The importance of phytoplankton size in mediating trophic interactions within the plankton of a southern African estuary
- Authors: Froneman, P William
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6928 , http://hdl.handle.net/10962/d1011944
- Description: The influence of the phytoplankton size composition in mediating the trophic interactions between the bacteria, phytoplankton, microheterotrophs (<200 μm) and mesozooplankton (>200 μm) was investigated on three occasions in a warm temperate, temporarily open/closed estuary situated along the southern African coastline. Results of the investigation indicated that the microheterotrophs represented the most important consumers of bacteria and chlorophyll (chl)-a <5.0 μm. The low impact of the mesozooplankton on the bacteria and chl-a <5.0 μm during the study appeared to be related to the inability of the larger zooplankton to feed efficiently on small particles. During those periods when total chl-a concentration was dominated by picophytoplankton (<2.0 μm) and microphytoplankton (>20 μm), mesozooplankton were unable to feed efficiently on the chl-a due to feeding constraints. In response to the unfavorable size structure of the phytoplankton assemblages, mesozooplankton appeared to consume the microheterotrophs. The negative impact of the mesozooplankton on the microheterotrophs resulted in a decrease in the impact of these organisms on the bacteria and the chl-a <5.0 μm. This result is consistent with the predator-prey cascades. On the other hand, when the total chl-a was dominated by nanophytoplankton (2–20 μm), mesozooplankton were able to feed directly on the phytoplankton. Results of the study indicate that size structure of the phytoplankton assemblages within estuaries plays an important role in mediating the trophic interactions between the various components of the plankton food web.
- Full Text:
- Date Issued: 2006
- Authors: Froneman, P William
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6928 , http://hdl.handle.net/10962/d1011944
- Description: The influence of the phytoplankton size composition in mediating the trophic interactions between the bacteria, phytoplankton, microheterotrophs (<200 μm) and mesozooplankton (>200 μm) was investigated on three occasions in a warm temperate, temporarily open/closed estuary situated along the southern African coastline. Results of the investigation indicated that the microheterotrophs represented the most important consumers of bacteria and chlorophyll (chl)-a <5.0 μm. The low impact of the mesozooplankton on the bacteria and chl-a <5.0 μm during the study appeared to be related to the inability of the larger zooplankton to feed efficiently on small particles. During those periods when total chl-a concentration was dominated by picophytoplankton (<2.0 μm) and microphytoplankton (>20 μm), mesozooplankton were unable to feed efficiently on the chl-a due to feeding constraints. In response to the unfavorable size structure of the phytoplankton assemblages, mesozooplankton appeared to consume the microheterotrophs. The negative impact of the mesozooplankton on the microheterotrophs resulted in a decrease in the impact of these organisms on the bacteria and the chl-a <5.0 μm. This result is consistent with the predator-prey cascades. On the other hand, when the total chl-a was dominated by nanophytoplankton (2–20 μm), mesozooplankton were able to feed directly on the phytoplankton. Results of the study indicate that size structure of the phytoplankton assemblages within estuaries plays an important role in mediating the trophic interactions between the various components of the plankton food web.
- Full Text:
- Date Issued: 2006
The Educational Journal
- Date: 2006-03
- Subjects: Education -- South Africa , Economics -- South Africa , South Africa -- Social conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/38279 , vital:34542 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2006-03
- Date: 2006-03
- Subjects: Education -- South Africa , Economics -- South Africa , South Africa -- Social conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/38279 , vital:34542 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2006-03
The Educational Journal
- Date: 2006-06
- Subjects: Education – South Africa , South Africa – Economic conditions , South Africa – Social conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/38309 , vital:34548 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2006-06
- Date: 2006-06
- Subjects: Education – South Africa , South Africa – Economic conditions , South Africa – Social conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/38309 , vital:34548 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2006-06
The Educational Journal
- Date: 2006-09
- Subjects: Education – South Africa , South Africa – Social conditions , South Africa – Economic conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/41199 , vital:36400 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2006-09
- Date: 2006-09
- Subjects: Education – South Africa , South Africa – Social conditions , South Africa – Economic conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/41199 , vital:36400 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2006-09
The Educational Journal
- Date: 2006-12
- Subjects: Education – South Africa , South Africa – Economic conditions , South Africa – Social conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/41677 , vital:36554 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2006-12
- Date: 2006-12
- Subjects: Education – South Africa , South Africa – Economic conditions , South Africa – Social conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/41677 , vital:36554 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2006-12
A stability-indicating high performance liquid chromatographic (HPLC) assay for the simultaneous determination of atorvastatin and amlodipine in commercial tablets
- Mohammadi, Ali, Rezanour, N, Ansari Dogaheh, M, Ghorbani Bidkorbeh, F, Hashem, M, Walker, Roderick B
- Authors: Mohammadi, Ali , Rezanour, N , Ansari Dogaheh, M , Ghorbani Bidkorbeh, F , Hashem, M , Walker, Roderick B
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6403 , http://hdl.handle.net/10962/d1006340
- Description: A simple, rapid, precise and accurate isocratic reversed-phase stability-indicating HPLC method was developed and validated for the simultaneous determination of atorvastatin (AT) and amlodipine (AM) in commercial tablets. The method has shown adequate separation for AM, AT from their associated main impurities and their degradation products. Separation was achieved on a Perfectsil® Target ODS-3, 5 μm, 250 mm × 4.6 mm i.d. column using a mobile phase consisting of acetonitrile–0.025 M NaH2PO4 buffer (pH 4.5) (55:45, v/v) at a flow rate of 1 ml/min and UV detection at 237 nm. The drugs were subjected to oxidation, hydrolysis, photolysis and heat to apply stress conditions. The linearity of the proposed method was investigated in the range of 2–30 μg/ml (r = 0.9994) for AT and 1–20 μg/ml (r = 0.9993) for AM. The limits of detection were 0.65 μg/ml and 0.35 μg/ml for AT and AM, respectively. The limits of quantitation were 2 μg/ml and 1 μg/ml for AT and AM, respectively. Degradation products produced as a result of stress studies did not interfere with the detection of AT and AM and the assay can thus be considered stability-indicating.
- Full Text:
- Date Issued: 2007
- Authors: Mohammadi, Ali , Rezanour, N , Ansari Dogaheh, M , Ghorbani Bidkorbeh, F , Hashem, M , Walker, Roderick B
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6403 , http://hdl.handle.net/10962/d1006340
- Description: A simple, rapid, precise and accurate isocratic reversed-phase stability-indicating HPLC method was developed and validated for the simultaneous determination of atorvastatin (AT) and amlodipine (AM) in commercial tablets. The method has shown adequate separation for AM, AT from their associated main impurities and their degradation products. Separation was achieved on a Perfectsil® Target ODS-3, 5 μm, 250 mm × 4.6 mm i.d. column using a mobile phase consisting of acetonitrile–0.025 M NaH2PO4 buffer (pH 4.5) (55:45, v/v) at a flow rate of 1 ml/min and UV detection at 237 nm. The drugs were subjected to oxidation, hydrolysis, photolysis and heat to apply stress conditions. The linearity of the proposed method was investigated in the range of 2–30 μg/ml (r = 0.9994) for AT and 1–20 μg/ml (r = 0.9993) for AM. The limits of detection were 0.65 μg/ml and 0.35 μg/ml for AT and AM, respectively. The limits of quantitation were 2 μg/ml and 1 μg/ml for AT and AM, respectively. Degradation products produced as a result of stress studies did not interfere with the detection of AT and AM and the assay can thus be considered stability-indicating.
- Full Text:
- Date Issued: 2007
Quality of life in South Africa: the first ten years of democracy
- Authors: Moller, Valerie
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:7110 , http://hdl.handle.net/10962/d1010741
- Description: South Africa celebrated ten years of democracy in 2004. This special issue of Social Indicators Research (SIR) reviews developments that have impacted on the quality of life of ordinary South Africans during the transition period. The issue updates an earlier volume of SIR (Volume 41) published in 1997 and as a stand-alone volume. The earlier volume was initiated following SIR editor Alex Michalos’ first visit to South Africa. This update on quality of life in South Africa follows on his return visit to the country in 2004 to see firsthand the changes that had occured in the meantime. This introductory article outlines major achievements of and setbacks for the new democracy and the challenges facing it in future. It provides the backround for the evaluations of a range of quality of life domains and issues including poverty and inequality, crime, the HIV/AIDS epidemic, migration and housing, religiosity, reconciliation, and optimism for the future which are covered in the eleven articles that follow. The introduction divides the articles under the headings of challenges, achievements, monitoring quality of life, and social capital for the future. The overview article concludes that improvements in quality of life have been uneven but goodwill and a positive outlook bode well for South African quality of life in future.
- Full Text:
- Date Issued: 2007
- Authors: Moller, Valerie
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:7110 , http://hdl.handle.net/10962/d1010741
- Description: South Africa celebrated ten years of democracy in 2004. This special issue of Social Indicators Research (SIR) reviews developments that have impacted on the quality of life of ordinary South Africans during the transition period. The issue updates an earlier volume of SIR (Volume 41) published in 1997 and as a stand-alone volume. The earlier volume was initiated following SIR editor Alex Michalos’ first visit to South Africa. This update on quality of life in South Africa follows on his return visit to the country in 2004 to see firsthand the changes that had occured in the meantime. This introductory article outlines major achievements of and setbacks for the new democracy and the challenges facing it in future. It provides the backround for the evaluations of a range of quality of life domains and issues including poverty and inequality, crime, the HIV/AIDS epidemic, migration and housing, religiosity, reconciliation, and optimism for the future which are covered in the eleven articles that follow. The introduction divides the articles under the headings of challenges, achievements, monitoring quality of life, and social capital for the future. The overview article concludes that improvements in quality of life have been uneven but goodwill and a positive outlook bode well for South African quality of life in future.
- Full Text:
- Date Issued: 2007
Spermiogenesis in three species of cicadas (Hemiptera: Cicadidae)
- Chawanji, A S, Hodgson, Alan N, Villet, Martin H, Sanborn, Allen F, Phillips, P K
- Authors: Chawanji, A S , Hodgson, Alan N , Villet, Martin H , Sanborn, Allen F , Phillips, P K
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6865 , http://hdl.handle.net/10962/d1011207
- Description: Spermiogenesis in three species of cicadas representing one cicadettine (Monomatapa matoposa Boulard) and two cicadines (Diceroprocta biconica [Walker] and Kongota punctigera [Walker]) was investigated by light and electron microscopy. Although spermiogenesis was occurring in the testis of adult males of all species, earlier spermiogenic stages were observed in D. biconica only. While spermiogenesis was similar to that described for other insects, some differences were noted. For example granular material did not assemble around the centriole to form a centriolar adjunct but did accumulate in the cytoplasm of early spermatids adjacent to a region of the nuclear membrane where nuclear pores were aggregated. In late spermatids this material accumulated anterior to the mitochondrial derivatives in a developing postero-lateral nuclear groove. While this material has been named the ‘centriolar adjunct’ by previous authors, its formation away from the centriole raises questions about its true identity. Second, during acrosome maturation an ante-acrosomal region of cytoplasm develops. Although present in later spermatids, this region is lost in spermatozoa. Interspecific variations in chromatin condensation patterns and the number of microtubule layers encircling the spermatid nucleus during spermiogenesis were noted.
- Full Text:
- Date Issued: 2007
- Authors: Chawanji, A S , Hodgson, Alan N , Villet, Martin H , Sanborn, Allen F , Phillips, P K
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6865 , http://hdl.handle.net/10962/d1011207
- Description: Spermiogenesis in three species of cicadas representing one cicadettine (Monomatapa matoposa Boulard) and two cicadines (Diceroprocta biconica [Walker] and Kongota punctigera [Walker]) was investigated by light and electron microscopy. Although spermiogenesis was occurring in the testis of adult males of all species, earlier spermiogenic stages were observed in D. biconica only. While spermiogenesis was similar to that described for other insects, some differences were noted. For example granular material did not assemble around the centriole to form a centriolar adjunct but did accumulate in the cytoplasm of early spermatids adjacent to a region of the nuclear membrane where nuclear pores were aggregated. In late spermatids this material accumulated anterior to the mitochondrial derivatives in a developing postero-lateral nuclear groove. While this material has been named the ‘centriolar adjunct’ by previous authors, its formation away from the centriole raises questions about its true identity. Second, during acrosome maturation an ante-acrosomal region of cytoplasm develops. Although present in later spermatids, this region is lost in spermatozoa. Interspecific variations in chromatin condensation patterns and the number of microtubule layers encircling the spermatid nucleus during spermiogenesis were noted.
- Full Text:
- Date Issued: 2007
Using the tutorial system to improve the quality of feedback to students in large class teaching
- Snowball, Jeanette D, Sayigh, E
- Authors: Snowball, Jeanette D , Sayigh, E
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70848 , vital:29752
- Description: In many universities, economics teachers now face the challenge of dealing with large, diverse classes, especially at undergraduate level. A common concern is the non-attendance at lectures of unmotivated (conscript) students. This paper presents the results of a student assessment of a macroeconomics 1 course, coupled with a self-assessment of their own input into the course. The results obtained, using an econometric model, suggest that what students do outside of lectures is equally, or more, important than lecture attendance itself. The paper concludes by examining the possibility of using peer assessed group learning as a feasible way to encourage deep learning in large classes.
- Full Text:
- Date Issued: 2007
- Authors: Snowball, Jeanette D , Sayigh, E
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70848 , vital:29752
- Description: In many universities, economics teachers now face the challenge of dealing with large, diverse classes, especially at undergraduate level. A common concern is the non-attendance at lectures of unmotivated (conscript) students. This paper presents the results of a student assessment of a macroeconomics 1 course, coupled with a self-assessment of their own input into the course. The results obtained, using an econometric model, suggest that what students do outside of lectures is equally, or more, important than lecture attendance itself. The paper concludes by examining the possibility of using peer assessed group learning as a feasible way to encourage deep learning in large classes.
- Full Text:
- Date Issued: 2007
The Educational Journal
- Date: 2007-03
- Subjects: Education – South Africa , South Africa – Social conditions , South Africa – Economic conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/41189 , vital:36399 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2007-03
- Date: 2007-03
- Subjects: Education – South Africa , South Africa – Social conditions , South Africa – Economic conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/41189 , vital:36399 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2007-03
The Educational Journal
- Date: 2007-09
- Subjects: Education – South Africa , South Africa – Social conditions , South Africa – Economic conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/41209 , vital:36401 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2007-09
- Date: 2007-09
- Subjects: Education – South Africa , South Africa – Social conditions , South Africa – Economic conditions
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/41209 , vital:36401 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa. From the 2000s, the journal was published by the National Union of Public Service and Allied Workers (NUPSAW), a trade union formed in August 1998 from the amalgamation of militant and moderate trade unions and also operated in the education sphere.
- Full Text: false
- Date Issued: 2007-09
Handling multiple levels of data and multiple research questions in an embedded case study : methodological challenges
- Authors: Edwards, David J A
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6247 , http://hdl.handle.net/10962/d1007865
- Description: Hougaard et al. report an embedded case study in which nine socially phobic clients were treated as part of a therapy program, which incorporated individual and group therapy and which was largely delivered by trainee clinicians. An important focus of the report is on the effectiveness of their treatment model. This commentary draws attention to the size and complexity of the available data, and it suggests ways in which the use of a more explicitly interpretative methodology can draw out additional dimensions of the data and allow a more systematic contribution to be made to the development of clinical theory.
- Full Text:
- Date Issued: 2008
- Authors: Edwards, David J A
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6247 , http://hdl.handle.net/10962/d1007865
- Description: Hougaard et al. report an embedded case study in which nine socially phobic clients were treated as part of a therapy program, which incorporated individual and group therapy and which was largely delivered by trainee clinicians. An important focus of the report is on the effectiveness of their treatment model. This commentary draws attention to the size and complexity of the available data, and it suggests ways in which the use of a more explicitly interpretative methodology can draw out additional dimensions of the data and allow a more systematic contribution to be made to the development of clinical theory.
- Full Text:
- Date Issued: 2008
Mimics and magnets : The importance of color and ecological facilitation in floral deception
- Peter, Craig I, Johnson, Steven D
- Authors: Peter, Craig I , Johnson, Steven D
- Date: 2008
- Identifier: vital:6536 , http://hdl.handle.net/10962/d1005977
- Description: Plants that lack floral rewards can attract pollinators if they share attractive floral signals with rewarding plants. These deceptive plants should benefit from flowering in close proximity to such rewarding plants, because pollinators are locally conditioned on floral signals of the rewarding plants (mimic effect) and because pollinators are more abundant close to rewarding plants (magnet effect). We tested these ideas using the non-rewarding South African plant Eulophia zeyheriana (Orchidaceae) as a study system. Field observations revealed that E. zeyheriana is pollinated solely by solitary bees belonging to a single species of Lipotriches (Halictidae) that appears to be closely associated with the flowers of Wahlenbergia cuspidata (Campanulaceae), a rewarding plant with which the orchid is often sympatric. The pale blue color of the flowers of E. zeyheriana differs strongly from flowers of its congeners, but is very similar to that of flowers of W. cuspidata. Analysis of spectral reflectance patterns using a bee vision model showed that bees are unlikely to be able to distinguish the two species in terms of flower color. A UV-absorbing sunscreen was applied to the flowers of the orchid in order to alter their color, and this resulted in a significant decline in pollinator visits, thus indicating the importance of flower color for attraction of Lipotriches bees. Pollination success in the orchid was strongly affected by proximity to patches of W. cuspidata. This was evident from one of two surveys of natural populations of the orchid, as well as experiments in which we translocated inflorescences of the orchid either into patches of W. cuspidata or 40 m outside such patches. Flower color and location of E. zeyheriana plants relative to rewarding magnet patches are therefore key components of the exploitation by this orchid of the relationship between W. cuspidata and Lipotriches bee pollinators.
- Full Text:
- Date Issued: 2008
- Authors: Peter, Craig I , Johnson, Steven D
- Date: 2008
- Identifier: vital:6536 , http://hdl.handle.net/10962/d1005977
- Description: Plants that lack floral rewards can attract pollinators if they share attractive floral signals with rewarding plants. These deceptive plants should benefit from flowering in close proximity to such rewarding plants, because pollinators are locally conditioned on floral signals of the rewarding plants (mimic effect) and because pollinators are more abundant close to rewarding plants (magnet effect). We tested these ideas using the non-rewarding South African plant Eulophia zeyheriana (Orchidaceae) as a study system. Field observations revealed that E. zeyheriana is pollinated solely by solitary bees belonging to a single species of Lipotriches (Halictidae) that appears to be closely associated with the flowers of Wahlenbergia cuspidata (Campanulaceae), a rewarding plant with which the orchid is often sympatric. The pale blue color of the flowers of E. zeyheriana differs strongly from flowers of its congeners, but is very similar to that of flowers of W. cuspidata. Analysis of spectral reflectance patterns using a bee vision model showed that bees are unlikely to be able to distinguish the two species in terms of flower color. A UV-absorbing sunscreen was applied to the flowers of the orchid in order to alter their color, and this resulted in a significant decline in pollinator visits, thus indicating the importance of flower color for attraction of Lipotriches bees. Pollination success in the orchid was strongly affected by proximity to patches of W. cuspidata. This was evident from one of two surveys of natural populations of the orchid, as well as experiments in which we translocated inflorescences of the orchid either into patches of W. cuspidata or 40 m outside such patches. Flower color and location of E. zeyheriana plants relative to rewarding magnet patches are therefore key components of the exploitation by this orchid of the relationship between W. cuspidata and Lipotriches bee pollinators.
- Full Text:
- Date Issued: 2008
The effects of load and gradient on hand force responses during dynamic pushing and pulling tasks
- Bennett, Anthea I, Desai, Sheena D, Todd, Andrew I, Freeland, H
- Authors: Bennett, Anthea I , Desai, Sheena D , Todd, Andrew I , Freeland, H
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6757 , http://hdl.handle.net/10962/d1009459
- Description: The limited attention afforded to push/pull activities and the motion phases (initial, sustained and ending) characteristic of these tasks has prompted a research focus in this area. The present study examined biomechanical responses in the form of hand forces during dynamic submaximal trolley pushing and pulling. Participants pushed/pulled loads of 100, 200 and 300 kg on the level (determining impact of load) or pushed 100 kg along a 12° ramp (uphill and downhill- determining impact of gradient). During level exertions significant differences (p<0.05) in hand forces occurred between loads of 100 and 200 kg, and 100 and 300 kg for initial and sustained forces but not ending forces. Values were similar for pushing and pulling at respective loads and motion phases. Strong correlations indicate that initial forces can be used to accurately estimate sustained and ending forces. Importantly, correct technique is essential in force reduction. Forces were highest during uphill initial and sustained phases and the downhill sustained phase. For the initial phase, the forces were highest during uphill pushing (86.5 ± 25.73 N); for the sustained phase, there was no difference between uphill and downhill forces but level forces were significantly lower (18.19 ± 8.09 N) than either of the other two conditions; for the ending phase, the highest forces were produced during downhill pushing (-53.34 ± 13.65N). As sustained forces equaled or exceeded initial forces for uphill and downhill efforts, consideration of sustained forces may be appropriate in determining the inherent potential risk of graded pushing.
- Full Text:
- Date Issued: 2008
- Authors: Bennett, Anthea I , Desai, Sheena D , Todd, Andrew I , Freeland, H
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6757 , http://hdl.handle.net/10962/d1009459
- Description: The limited attention afforded to push/pull activities and the motion phases (initial, sustained and ending) characteristic of these tasks has prompted a research focus in this area. The present study examined biomechanical responses in the form of hand forces during dynamic submaximal trolley pushing and pulling. Participants pushed/pulled loads of 100, 200 and 300 kg on the level (determining impact of load) or pushed 100 kg along a 12° ramp (uphill and downhill- determining impact of gradient). During level exertions significant differences (p<0.05) in hand forces occurred between loads of 100 and 200 kg, and 100 and 300 kg for initial and sustained forces but not ending forces. Values were similar for pushing and pulling at respective loads and motion phases. Strong correlations indicate that initial forces can be used to accurately estimate sustained and ending forces. Importantly, correct technique is essential in force reduction. Forces were highest during uphill initial and sustained phases and the downhill sustained phase. For the initial phase, the forces were highest during uphill pushing (86.5 ± 25.73 N); for the sustained phase, there was no difference between uphill and downhill forces but level forces were significantly lower (18.19 ± 8.09 N) than either of the other two conditions; for the ending phase, the highest forces were produced during downhill pushing (-53.34 ± 13.65N). As sustained forces equaled or exceeded initial forces for uphill and downhill efforts, consideration of sustained forces may be appropriate in determining the inherent potential risk of graded pushing.
- Full Text:
- Date Issued: 2008
APDUSA Views
- Date: 2008-09
- Subjects: Government, Resistance to -- South Africa , South Africa -- History -- 20th century , South Africa -- Politics and government
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/33649 , vital:32912 , Bulk File 7
- Description: APDUSA Views was published by the African People’s Democratic Union of Southern Africa (Natal), an affiliate of the New Unity Movement.
- Full Text: false
- Date Issued: 2008-09
- Date: 2008-09
- Subjects: Government, Resistance to -- South Africa , South Africa -- History -- 20th century , South Africa -- Politics and government
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/33649 , vital:32912 , Bulk File 7
- Description: APDUSA Views was published by the African People’s Democratic Union of Southern Africa (Natal), an affiliate of the New Unity Movement.
- Full Text: false
- Date Issued: 2008-09
A test for Allee effects in the self-incompatible wasp-pollinated milkweed Gomphocarpus physocarpus
- Coombs, Gareth, Peter, Craig I, Johnson, Steven D
- Authors: Coombs, Gareth , Peter, Craig I , Johnson, Steven D
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6511 , http://hdl.handle.net/10962/d1005938 , http://dx.doi.org/10.1111/j.1442-9993.2009.01976.x
- Description: It has been suggested that plants which are good colonizers will generally have either an ability to self-fertilize or a generalist pollination system. This prediction is based on the idea that these reproductive traits should confer resistance to Allee effects in founder populations and was tested using Gomphocarpus physocarpus (Asclepiadoideae; Apocynaceae), a species native to South Africa that is invasive in other parts of the world. We found no significant relationships between the size of G. physocarpus populations and various measures of pollination success (pollen deposition, pollen removal, and pollen transfer efficiency) and fruit set. A breeding system experiment showed that plants in a South African population are genetically self-incompatible and thus obligate outcrossers. Out-crossing is further enhanced by mechanical reconfiguration of removed pollinaria before the pollinia can be deposited. Selfpollination is reduced when such reconfiguration exceeds the average duration of pollinator visits to a plant. Observations suggest that a wide variety of wasp species in the genera Belonogaster and Polistes (Vespidae) are the primary pollinators. We conclude that efficient pollination of plants in small founding populations, resulting from their generalist wasp-pollination system, contributes in part to the colonizing success of G. physocarpus. The presence of similar wasps in other parts of the world has evidently facilitated the expansion of the range of this milkweed.
- Full Text:
- Date Issued: 2009
- Authors: Coombs, Gareth , Peter, Craig I , Johnson, Steven D
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6511 , http://hdl.handle.net/10962/d1005938 , http://dx.doi.org/10.1111/j.1442-9993.2009.01976.x
- Description: It has been suggested that plants which are good colonizers will generally have either an ability to self-fertilize or a generalist pollination system. This prediction is based on the idea that these reproductive traits should confer resistance to Allee effects in founder populations and was tested using Gomphocarpus physocarpus (Asclepiadoideae; Apocynaceae), a species native to South Africa that is invasive in other parts of the world. We found no significant relationships between the size of G. physocarpus populations and various measures of pollination success (pollen deposition, pollen removal, and pollen transfer efficiency) and fruit set. A breeding system experiment showed that plants in a South African population are genetically self-incompatible and thus obligate outcrossers. Out-crossing is further enhanced by mechanical reconfiguration of removed pollinaria before the pollinia can be deposited. Selfpollination is reduced when such reconfiguration exceeds the average duration of pollinator visits to a plant. Observations suggest that a wide variety of wasp species in the genera Belonogaster and Polistes (Vespidae) are the primary pollinators. We conclude that efficient pollination of plants in small founding populations, resulting from their generalist wasp-pollination system, contributes in part to the colonizing success of G. physocarpus. The presence of similar wasps in other parts of the world has evidently facilitated the expansion of the range of this milkweed.
- Full Text:
- Date Issued: 2009
De La Rey rides (yet) again : Afrikaner identity politics and nostalgia in post-apartheid South Africa
- Authors: Baines, Gary F
- Date: 2009
- Language: English
- Type: Conference paper
- Identifier: vital:6158 , http://hdl.handle.net/10962/d1007078
- Description: In 2006 a relatively unknown South African artist with the stage name Bok van Blerk released his debut album called “De la Rey”. The album included a music video of the title track that calls upon the legendary Boer War general to save the volk (people) from the wantonly destructive strategies of the British imperial forces: the scorched earth policy and the subsequent internment of women and children in concentration camps. The British justified such extreme – some would say ‘genocidal’ – strategies so as to prevent non-combatants from supporting the irregular Boer soldiers. Although he did not believe that the war could be won on account of the overwhelming odds that the Boer forces faced, De la Rey still fought to the bitter end. Needless to say, he was on the losing side.
- Full Text:
- Date Issued: 2009
- Authors: Baines, Gary F
- Date: 2009
- Language: English
- Type: Conference paper
- Identifier: vital:6158 , http://hdl.handle.net/10962/d1007078
- Description: In 2006 a relatively unknown South African artist with the stage name Bok van Blerk released his debut album called “De la Rey”. The album included a music video of the title track that calls upon the legendary Boer War general to save the volk (people) from the wantonly destructive strategies of the British imperial forces: the scorched earth policy and the subsequent internment of women and children in concentration camps. The British justified such extreme – some would say ‘genocidal’ – strategies so as to prevent non-combatants from supporting the irregular Boer soldiers. Although he did not believe that the war could be won on account of the overwhelming odds that the Boer forces faced, De la Rey still fought to the bitter end. Needless to say, he was on the losing side.
- Full Text:
- Date Issued: 2009
Investigating how the attributes of live theatre productions influence consumption choices using conjoint analysis : the example of the National Arts Festival, South Africa
- Willis, K G, Snowball, Jeanette D
- Authors: Willis, K G , Snowball, Jeanette D
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6075 , http://hdl.handle.net/10962/d1003825 , http://dx.doi.org/10.1007/s10824-009-9097-z
- Description: While there is a fair amount of work on determinants of demand for the live performing arts, results have often been contradictory with little explanatory power. This may be because of the difficulty in describing the attributes of a performance, particularly in terms of its quality, and the heterogeneity of consumer preferences. This article uses conjoint analysis, also called choice experiments, to investigate the impact of the attributes of live theatre performances on demand, using data collected from 483 randomly chosen attenders at live theatre performances at the 2008 South African National Arts Festival. Attributes include the type of cast (professional, semi-professional or amateur), reputation of the producer/director, the context or setting, production type and ticket price of the show. Results largely support the a priori expectations based on the results of other demand studies. For example, it is found that the age of consumers affects the type of show chosen, that utility and willingness to pay increase for shows with professional and semi-professional casts and that 93% of the potential audience prefer shows with a South African context. It is concluded that the method could prove useful to both event organisers and policy makers, especially where the goal is to broaden access to the arts.
- Full Text:
- Date Issued: 2009
- Authors: Willis, K G , Snowball, Jeanette D
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6075 , http://hdl.handle.net/10962/d1003825 , http://dx.doi.org/10.1007/s10824-009-9097-z
- Description: While there is a fair amount of work on determinants of demand for the live performing arts, results have often been contradictory with little explanatory power. This may be because of the difficulty in describing the attributes of a performance, particularly in terms of its quality, and the heterogeneity of consumer preferences. This article uses conjoint analysis, also called choice experiments, to investigate the impact of the attributes of live theatre performances on demand, using data collected from 483 randomly chosen attenders at live theatre performances at the 2008 South African National Arts Festival. Attributes include the type of cast (professional, semi-professional or amateur), reputation of the producer/director, the context or setting, production type and ticket price of the show. Results largely support the a priori expectations based on the results of other demand studies. For example, it is found that the age of consumers affects the type of show chosen, that utility and willingness to pay increase for shows with professional and semi-professional casts and that 93% of the potential audience prefer shows with a South African context. It is concluded that the method could prove useful to both event organisers and policy makers, especially where the goal is to broaden access to the arts.
- Full Text:
- Date Issued: 2009
Mulch tower treatment system for greywater reuse Part II: destructive testing and effluent treatment
- Tandlich, Roman, Zuma, Bongumusa M, Whittington-Jones, Kevin J, Burgess, Jo E
- Authors: Tandlich, Roman , Zuma, Bongumusa M , Whittington-Jones, Kevin J , Burgess, Jo E
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71547 , vital:29863 , https://doi.org/10.1016/j.desal.2008.03.031
- Description: The mulch tower (MT) system described in Part I was tested to failure to determine its range of operating conditions. An increase in the influent temperature led to a statistically significant release of components of the chemical oxygen demand (COD) and the five day biochemical oxygen demand (BOD5), as well as phosphates from the MT system. Heterotrophic plate count (HPC) of the mulch layer dropped from 1.2 (± 0.6) × 106/g dry weight to 1.5 (± 0.3) × 105/g dry weight of the mulch layer with increases of the influent temperature. This indicates that the increase in influent temperature killed off some of the active biomass in the MT biofilm. After a five day drying period under active aeration, the MT system retained the ability to remove COD, total suspended solids (TSS), and nitrates. Greywater treatment by the MT system became impossible after a 48 day drying period under active aeration. Chlorination of the simulated MT effluent with a mixture of sodium dichloroisocyanurate and trichloroisocyanuric acid decreased the faecal coliform concentrations (FC) and the total coliform concentrations (TC) below 800 CFUs/100 ml within 65 h. Beyond 65 h, the pH of the effluent became highly acidic. To maintain optimum performance influent should be fed into the MT system at least once every 5 days, sufficient aeration should be guaranteed, and the MT effluent should be chlorinated for 65 h to eliminate all pathogens before any reuse.
- Full Text: false
- Date Issued: 2009
Mulch tower treatment system for greywater reuse Part II: destructive testing and effluent treatment
- Authors: Tandlich, Roman , Zuma, Bongumusa M , Whittington-Jones, Kevin J , Burgess, Jo E
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71547 , vital:29863 , https://doi.org/10.1016/j.desal.2008.03.031
- Description: The mulch tower (MT) system described in Part I was tested to failure to determine its range of operating conditions. An increase in the influent temperature led to a statistically significant release of components of the chemical oxygen demand (COD) and the five day biochemical oxygen demand (BOD5), as well as phosphates from the MT system. Heterotrophic plate count (HPC) of the mulch layer dropped from 1.2 (± 0.6) × 106/g dry weight to 1.5 (± 0.3) × 105/g dry weight of the mulch layer with increases of the influent temperature. This indicates that the increase in influent temperature killed off some of the active biomass in the MT biofilm. After a five day drying period under active aeration, the MT system retained the ability to remove COD, total suspended solids (TSS), and nitrates. Greywater treatment by the MT system became impossible after a 48 day drying period under active aeration. Chlorination of the simulated MT effluent with a mixture of sodium dichloroisocyanurate and trichloroisocyanuric acid decreased the faecal coliform concentrations (FC) and the total coliform concentrations (TC) below 800 CFUs/100 ml within 65 h. Beyond 65 h, the pH of the effluent became highly acidic. To maintain optimum performance influent should be fed into the MT system at least once every 5 days, sufficient aeration should be guaranteed, and the MT effluent should be chlorinated for 65 h to eliminate all pathogens before any reuse.
- Full Text: false
- Date Issued: 2009
On location: Narratives of the South African city of the late 1940s and 1950s in film and literature
- Authors: Baines, Gary F
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125397 , vital:35779 , https://doi.10.1080/02582470308671922
- Description: This article is about narratives, about the forms and meanings constructed by South African storytellers, especially writers and filmmakers. It examines the relationships between examples of these two different narrative forms of literature (fiction and non-fiction) and feature film. Following Turner, the point of departure is that the study of narrative has the potential to provide a framework within which such a two pronged approach can be undertaken. This is not to say that the production of meaning takes place within an exclusive literary or cinematic context. Rather, this approach will allow us to obtain a fuller picture of the narrative of the South African city than is possible by concentrating on one medium. It is based on the premise that narratives are ultimately produced by culture; thus these cultural constructions generate meanings, take on a significance, and assume forms that are articufations of the values, beliefs -the ideology - of the culture.' Literature and film offer specific forms for such narratives. By adopting an interdisciplinary approach which borrows insights from literary and film studies, this article attempts to make a contribution to the fledgling field of South African cultural studies.
- Full Text:
- Date Issued: 2009
On location: Narratives of the South African city of the late 1940s and 1950s in film and literature
- Authors: Baines, Gary F
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125397 , vital:35779 , https://doi.10.1080/02582470308671922
- Description: This article is about narratives, about the forms and meanings constructed by South African storytellers, especially writers and filmmakers. It examines the relationships between examples of these two different narrative forms of literature (fiction and non-fiction) and feature film. Following Turner, the point of departure is that the study of narrative has the potential to provide a framework within which such a two pronged approach can be undertaken. This is not to say that the production of meaning takes place within an exclusive literary or cinematic context. Rather, this approach will allow us to obtain a fuller picture of the narrative of the South African city than is possible by concentrating on one medium. It is based on the premise that narratives are ultimately produced by culture; thus these cultural constructions generate meanings, take on a significance, and assume forms that are articufations of the values, beliefs -the ideology - of the culture.' Literature and film offer specific forms for such narratives. By adopting an interdisciplinary approach which borrows insights from literary and film studies, this article attempts to make a contribution to the fledgling field of South African cultural studies.
- Full Text:
- Date Issued: 2009