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
Introduction and extinction of brown trout (Salmo trutta L.) in an impoverished subantarctic stream
- Cooper, J, Crafford, J E, Hecht, Thomas
- Authors: Cooper, J , Crafford, J E , Hecht, Thomas
- Date: 1992
- Subjects: Anadromous fishes -- Marion Island
- Language: English
- Type: Article
- Identifier: vital:6767 , http://hdl.handle.net/10962/d1008044
- Description: Brown trout were introduced to the Van den Boogaard River on subantarctic Marion Island in 1964, and a small population became established. The last individual was seen in 1984, and the species is now considered to be extinct on the island. Their diet was exclusively allochthonous, with snails and spiders predominating. Ages estimated at six to eleven years showed that spawning must have occurred since the original introduction. Since the Van den Boogaard River enters the sea via a waterfall, it is postulated that trout were not able to practice an anadromous life-style, and that this, as well as other factors connected with the impoverished nature of the stream, led to dwarfing of the resident population. No further introductions of alien fish to Marion Island should be contemplated.
- Full Text:
- Date Issued: 1992
- Authors: Cooper, J , Crafford, J E , Hecht, Thomas
- Date: 1992
- Subjects: Anadromous fishes -- Marion Island
- Language: English
- Type: Article
- Identifier: vital:6767 , http://hdl.handle.net/10962/d1008044
- Description: Brown trout were introduced to the Van den Boogaard River on subantarctic Marion Island in 1964, and a small population became established. The last individual was seen in 1984, and the species is now considered to be extinct on the island. Their diet was exclusively allochthonous, with snails and spiders predominating. Ages estimated at six to eleven years showed that spawning must have occurred since the original introduction. Since the Van den Boogaard River enters the sea via a waterfall, it is postulated that trout were not able to practice an anadromous life-style, and that this, as well as other factors connected with the impoverished nature of the stream, led to dwarfing of the resident population. No further introductions of alien fish to Marion Island should be contemplated.
- Full Text:
- Date Issued: 1992
Disgraceland: history and the humanities in frontier country
- Authors: Cornwell, Gareth D N
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6117 , http://hdl.handle.net/10962/d1004618
- Description: This paper explores the significance of Coetzee's choice of Salem in the Eastern Cape as the (part) setting for his novel Disgrace. A determinedly local and historical reading of the text suggests that Lucy's conduct represents an "ideal" solution to the historical issues of wrong and reparation raised in the novel. This finding is scrutinized through a reading of "The Humanities in Africa" from Elizabeth Costello, and it is concluded that whatever hope for rehabilitation or redemption the novel holds out for white South Africans necessarily exists beyond the discourse of the humanities, indeed, outside of history itself.
- Full Text:
- Date Issued: 2003
- Authors: Cornwell, Gareth D N
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6117 , http://hdl.handle.net/10962/d1004618
- Description: This paper explores the significance of Coetzee's choice of Salem in the Eastern Cape as the (part) setting for his novel Disgrace. A determinedly local and historical reading of the text suggests that Lucy's conduct represents an "ideal" solution to the historical issues of wrong and reparation raised in the novel. This finding is scrutinized through a reading of "The Humanities in Africa" from Elizabeth Costello, and it is concluded that whatever hope for rehabilitation or redemption the novel holds out for white South Africans necessarily exists beyond the discourse of the humanities, indeed, outside of history itself.
- Full Text:
- Date Issued: 2003
"He and His Man": allegory and catachresis in J. M. Coetzee's Nobel Lecture
- Authors: Cornwell, Gareth D N
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:2261 , http://hdl.handle.net/10962/d1004619
- Description: This essay offers a reading of J.M. Coetzee's 2003 Nobel Lecture, "He and His Man," a narrative featuring the characters of Robinson Crusoe and Daniel Defoe that borrows extensively from Defoe's Journal of the Plague Year (1722) and Tour through the Whole Island of Great Britain (1724-26). In it Coetzee whimsically explores several concerns of central importance for the activities of reading and writing, most notably the seemingly unavoidable (though ostensibly disabling) phenomenon of displacement or substitution that -- at its most generalizable level -- is best characterized as catachresis.
- Full Text:
- Date Issued: 2007
- Authors: Cornwell, Gareth D N
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:2261 , http://hdl.handle.net/10962/d1004619
- Description: This essay offers a reading of J.M. Coetzee's 2003 Nobel Lecture, "He and His Man," a narrative featuring the characters of Robinson Crusoe and Daniel Defoe that borrows extensively from Defoe's Journal of the Plague Year (1722) and Tour through the Whole Island of Great Britain (1724-26). In it Coetzee whimsically explores several concerns of central importance for the activities of reading and writing, most notably the seemingly unavoidable (though ostensibly disabling) phenomenon of displacement or substitution that -- at its most generalizable level -- is best characterized as catachresis.
- Full Text:
- Date Issued: 2007
Don Maclennan (1929-2009): obituary
- Authors: Cornwell, Gareth D N
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6118 , http://hdl.handle.net/10962/d1004620
- Description: Donald Alasdair Calum Maclennan, the South African playwright, poet and critic, died in Port Elizabeth on February 9, 2009, at the age of 79. He will be remembered chiefly for the poetry that he published in the last three decades of his life.
- Full Text:
- Date Issued: 2009
- Authors: Cornwell, Gareth D N
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6118 , http://hdl.handle.net/10962/d1004620
- Description: Donald Alasdair Calum Maclennan, the South African playwright, poet and critic, died in Port Elizabeth on February 9, 2009, at the age of 79. He will be remembered chiefly for the poetry that he published in the last three decades of his life.
- Full Text:
- Date Issued: 2009
Jazz forum: Mongezi Feza
- Authors: Cotterrell, Roger
- Subjects: McGregor, Chris--1936-1990 , Feza, Mongezi , Brotherhood of Breath (Musical group) , Jazz , Jazz musicians
- Language: English
- Type: Article
- Identifier: vital:13522 , http://hdl.handle.net/10962/d1006099 , McGregor, Chris--1936-1990 , Feza, Mongezi , Brotherhood of Breath (Musical group) , Jazz , Jazz musicians
- Description: Photocopied article from the magazine Jazz Forum about Mongezi Feza's death.
- Full Text:
- Authors: Cotterrell, Roger
- Subjects: McGregor, Chris--1936-1990 , Feza, Mongezi , Brotherhood of Breath (Musical group) , Jazz , Jazz musicians
- Language: English
- Type: Article
- Identifier: vital:13522 , http://hdl.handle.net/10962/d1006099 , McGregor, Chris--1936-1990 , Feza, Mongezi , Brotherhood of Breath (Musical group) , Jazz , Jazz musicians
- Description: Photocopied article from the magazine Jazz Forum about Mongezi Feza's death.
- Full Text:
Stuffed birds on trees: an historical review of avian systematics in southern Africa
- Authors: Craig, Adrian J F K
- Date: 2000
- Language: English
- Type: Article
- Identifier: vital:6931 , http://hdl.handle.net/10962/d1011949
- Description: Avian systematics in southern Africa has been heavily dependent on a small number of museum-based specialists. They produced bird checklists which prescribed the names to be used by other scientists. After an initial phase of cataloguing the avifauna, a major preoccupation was the description of geographical variation, which was documented in an extensive subspecific nomenclature. Until recent years, few African ornithologists have been involved in systematics as a biological discipline. This historical overview considers the contribution of particular individuals from Andrew Smith to Phillip Clancey.
- Full Text: false
- Date Issued: 2000
- Authors: Craig, Adrian J F K
- Date: 2000
- Language: English
- Type: Article
- Identifier: vital:6931 , http://hdl.handle.net/10962/d1011949
- Description: Avian systematics in southern Africa has been heavily dependent on a small number of museum-based specialists. They produced bird checklists which prescribed the names to be used by other scientists. After an initial phase of cataloguing the avifauna, a major preoccupation was the description of geographical variation, which was documented in an extensive subspecific nomenclature. Until recent years, few African ornithologists have been involved in systematics as a biological discipline. This historical overview considers the contribution of particular individuals from Andrew Smith to Phillip Clancey.
- Full Text: false
- Date Issued: 2000
Iris colour in passerine birds: why be bright-eyed?
- Craig, Adrian J F K, Hulley, Patrick E
- Authors: Craig, Adrian J F K , Hulley, Patrick E
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6902 , http://hdl.handle.net/10962/d1011756
- Description: An initial survey of iris coloration in passerine birds (Aves: Passeriformes) showed that a brightly pigmented iris is much more common in southern African and Australian birds than in those from Europe, temperate North America, and Venezuela. However, the only statistical correlation reflected the distribution of particular bird families in these regions. Ten family-level groups considered to represent monophyletic taxa were then selected for a more detailed analysis, comparing iris coloration with distribution, status, taxonomy, plumage patterns, and some biological and behavioural characters for 1143 species. No pattern associating iris colour with particular traits was common to all families, but within families there were statistically significant associations with both plumage and biology. Our expectation that social behaviour would be an important predictor of iris colour was not supported, but critical information is still lacking for many species. Future studies of avian behavioural ecology should examine critically the role of iris coloration in individual species. , Rhodes Centenary issue
- Full Text:
- Date Issued: 2004
- Authors: Craig, Adrian J F K , Hulley, Patrick E
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6902 , http://hdl.handle.net/10962/d1011756
- Description: An initial survey of iris coloration in passerine birds (Aves: Passeriformes) showed that a brightly pigmented iris is much more common in southern African and Australian birds than in those from Europe, temperate North America, and Venezuela. However, the only statistical correlation reflected the distribution of particular bird families in these regions. Ten family-level groups considered to represent monophyletic taxa were then selected for a more detailed analysis, comparing iris coloration with distribution, status, taxonomy, plumage patterns, and some biological and behavioural characters for 1143 species. No pattern associating iris colour with particular traits was common to all families, but within families there were statistically significant associations with both plumage and biology. Our expectation that social behaviour would be an important predictor of iris colour was not supported, but critical information is still lacking for many species. Future studies of avian behavioural ecology should examine critically the role of iris coloration in individual species. , Rhodes Centenary issue
- Full Text:
- Date Issued: 2004
A common framework for lattice-valued uniform spaces and probabilistic uniform limit spaces
- Craig, Andrew, Jäger, Gunter
- Authors: Craig, Andrew , Jäger, Gunter
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6784 , http://hdl.handle.net/10962/d1006927
- Description: We study a category of lattice-valued uniform convergence spaces where the lattice is enriched by two algebraic operations. This general setting allows us to view the category of lattice-valued uniform spaces as a reflective subcategory of our category, and the category of probabilistic uniform limit spaces as a coreflective subcategory.
- Full Text:
- Date Issued: 2009
- Authors: Craig, Andrew , Jäger, Gunter
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6784 , http://hdl.handle.net/10962/d1006927
- Description: We study a category of lattice-valued uniform convergence spaces where the lattice is enriched by two algebraic operations. This general setting allows us to view the category of lattice-valued uniform spaces as a reflective subcategory of our category, and the category of probabilistic uniform limit spaces as a coreflective subcategory.
- Full Text:
- Date Issued: 2009
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
An approach to anaemia diagnosis – concerns in primary care
- Authors: D O’Mahony , M Mntonintshi
- Date: 2017
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/5616 , vital:44615
- Full Text:
- Authors: D O’Mahony , M Mntonintshi
- Date: 2017
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/5616 , vital:44615
- Full Text:
The effects of gold coated and uncoated zinc oxide nanohexagons on the photophysicochemical properties of the low symmetry zinc phthalocyanine
- D'Souza, Sarah, Ogbodu, Racheal O, Nyokong, Tebello
- Authors: D'Souza, Sarah , Ogbodu, Racheal O , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7280 , http://hdl.handle.net/10962/d1020317
- Description: A new low symmetry, Zn phthalocyanine monosubstituted with diethylaminoethanethiol (mDEAET ZnPc) was synthesized and characterized. This work reports on its photophysical and photochemical properties of mDEAET ZnPc alone and when conjugated to gold coated and uncoated zinc oxide nanohexagons (ZnO NHXs). The photophysicochemical properties generally improved in the presence of the ZnO NHXs. These complexes were also tested for their photodynamic antimicrobial activity against Staphylococcus aureus (S. aureus). The Pc alone showed remarkable growth inhibition even at concentrations as low as 0.05 mg/mL. The conjugates showed a high photoinactivation of S. aureus after 30 min at a fluence of 90 mW cm−2 at a concentration of 0.05 mg/mL. The ZnPc-ZnO NHX conjugates produced the best antimicrobial results. , Original publication is available at http://dx.doi.org/10.1016/j.molstruc.2015.06.088
- Full Text: false
- Authors: D'Souza, Sarah , Ogbodu, Racheal O , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7280 , http://hdl.handle.net/10962/d1020317
- Description: A new low symmetry, Zn phthalocyanine monosubstituted with diethylaminoethanethiol (mDEAET ZnPc) was synthesized and characterized. This work reports on its photophysical and photochemical properties of mDEAET ZnPc alone and when conjugated to gold coated and uncoated zinc oxide nanohexagons (ZnO NHXs). The photophysicochemical properties generally improved in the presence of the ZnO NHXs. These complexes were also tested for their photodynamic antimicrobial activity against Staphylococcus aureus (S. aureus). The Pc alone showed remarkable growth inhibition even at concentrations as low as 0.05 mg/mL. The conjugates showed a high photoinactivation of S. aureus after 30 min at a fluence of 90 mW cm−2 at a concentration of 0.05 mg/mL. The ZnPc-ZnO NHX conjugates produced the best antimicrobial results. , Original publication is available at http://dx.doi.org/10.1016/j.molstruc.2015.06.088
- Full Text: false
Non-steroidal anti-inflammatory agents, tolmetin and sulindac, inhibit liver tryptophan 2,3-dioxygenase activity and alter brain neurotransmitter levels
- Dairam, A, Antunes, Edith M, Saravanan, K S, Daya, Santylal
- Authors: Dairam, A , Antunes, Edith M , Saravanan, K S , Daya, Santylal
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6358 , http://hdl.handle.net/10962/d1006050 , http://dx.doi.org/10.1016/j.lfs.2006.07.028
- Description: Hepatic tryptophan 2,3-dioxygenase (TDO) is one of the rate-limiting enzymes in tryptophan catabolism and plays an important role in regulating the physiological flux of tryptophan into relevant metabolic pathways. In this study, we determined the effect of the non-steroidal anti-inflammatory agents, tolmetin and sulindac, on rat liver TDO activity and the subsequent changes in the hippocampal and striatal neurotransmitter levels. The amount of melatonin produced by the pineal gland was also measured using high performance liquid chromatography (HPLC). Treatment of rats with tolmetin or sulindac (5 mg/kg/bd for 5 days) significantly inhibited liver TDO activity. The results show that whilst tolmetin and sulindac increase serotonin levels in the hippocampus, these agents also significantly reduce dopamine levels in the striatum. Tolmetin, but not sulindac, increased the amount of melatonin produced by the pineal gland. The results of this study suggest that whilst tolmetin and sulindac may be beneficial for patients suffering from depression, these agents also have the potential to induce adverse effects in patients suffering with neurological disorders such as Parkinson's disease.
- Full Text:
- Date Issued: 2006
- Authors: Dairam, A , Antunes, Edith M , Saravanan, K S , Daya, Santylal
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6358 , http://hdl.handle.net/10962/d1006050 , http://dx.doi.org/10.1016/j.lfs.2006.07.028
- Description: Hepatic tryptophan 2,3-dioxygenase (TDO) is one of the rate-limiting enzymes in tryptophan catabolism and plays an important role in regulating the physiological flux of tryptophan into relevant metabolic pathways. In this study, we determined the effect of the non-steroidal anti-inflammatory agents, tolmetin and sulindac, on rat liver TDO activity and the subsequent changes in the hippocampal and striatal neurotransmitter levels. The amount of melatonin produced by the pineal gland was also measured using high performance liquid chromatography (HPLC). Treatment of rats with tolmetin or sulindac (5 mg/kg/bd for 5 days) significantly inhibited liver TDO activity. The results show that whilst tolmetin and sulindac increase serotonin levels in the hippocampus, these agents also significantly reduce dopamine levels in the striatum. Tolmetin, but not sulindac, increased the amount of melatonin produced by the pineal gland. The results of this study suggest that whilst tolmetin and sulindac may be beneficial for patients suffering from depression, these agents also have the potential to induce adverse effects in patients suffering with neurological disorders such as Parkinson's disease.
- Full Text:
- Date Issued: 2006
First results on bathymetry, stratification and physicochemical limnology of a small tropical African reservoir (Malilangwe, Zimbabwe)
- Dalu, Tatena, Thackeray, Zane, Leuci, Rio, Clegg, Bruce, Chari, Lenin D, Nhiwatiwa, Tamuka
- Authors: Dalu, Tatena , Thackeray, Zane , Leuci, Rio , Clegg, Bruce , Chari, Lenin D , Nhiwatiwa, Tamuka
- Date: 2013-01-11
- Language: English
- Type: Article
- Identifier: vital:6970 , http://hdl.handle.net/10962/d1013297
- Description: The study provides a 9-month record of Malilangwe Reservoir water chemistry periodicity, for the period between February and October 2011. Malilangwe Reservoir is a small (211 ha), shallow (mean depth 4.54 m) reservoir situated in the south-eastern lowveld of Zimbabwe. The reservoir has not spilled in nearly 11 years, which makes it a unique system as most reservoirs of comparable size spill annually. This is the first bathymetric and limnological study of the reservoir where the morphology and physicochemical quality of the water body were examined. The reservoir was not strongly stratified during the hot-wet and hot-dry season with oxygen depletion of < 2 mg·ℓ-1 DO being observed in the bottom layers (<6 m depth). Nutrient concentrations varied throughout the seasons. The reservoir exhibited marked seasonal fluctuations in water level, which decreased by over 149 cm between February and October. The N:P ratio rose to as high as 10.9 and generally reflected high levels of phosphorus in the reservoir. There were significant differences (p<0.05) in Secchi depth transparency between the study sites. Differences observed in water quality were due to water level fluctuations, with poor water quality conditions being experienced during the hot-dry season and the cool-dry season when water levels were low. The reservoir was classified as being mesotrophic. Therefore, there is a risk of eutrophication, especially since the reservoir is currently merely a sink for nutrients.
- Full Text:
- Authors: Dalu, Tatena , Thackeray, Zane , Leuci, Rio , Clegg, Bruce , Chari, Lenin D , Nhiwatiwa, Tamuka
- Date: 2013-01-11
- Language: English
- Type: Article
- Identifier: vital:6970 , http://hdl.handle.net/10962/d1013297
- Description: The study provides a 9-month record of Malilangwe Reservoir water chemistry periodicity, for the period between February and October 2011. Malilangwe Reservoir is a small (211 ha), shallow (mean depth 4.54 m) reservoir situated in the south-eastern lowveld of Zimbabwe. The reservoir has not spilled in nearly 11 years, which makes it a unique system as most reservoirs of comparable size spill annually. This is the first bathymetric and limnological study of the reservoir where the morphology and physicochemical quality of the water body were examined. The reservoir was not strongly stratified during the hot-wet and hot-dry season with oxygen depletion of < 2 mg·ℓ-1 DO being observed in the bottom layers (<6 m depth). Nutrient concentrations varied throughout the seasons. The reservoir exhibited marked seasonal fluctuations in water level, which decreased by over 149 cm between February and October. The N:P ratio rose to as high as 10.9 and generally reflected high levels of phosphorus in the reservoir. There were significant differences (p<0.05) in Secchi depth transparency between the study sites. Differences observed in water quality were due to water level fluctuations, with poor water quality conditions being experienced during the hot-dry season and the cool-dry season when water levels were low. The reservoir was classified as being mesotrophic. Therefore, there is a risk of eutrophication, especially since the reservoir is currently merely a sink for nutrients.
- Full Text:
Attitudes of Xhosa-speaking students at the University of Fort Hare towards the use of Xhosa as a language of learning and teaching (LOLT)
- Dalvit, Lorenzo, De Klerk, Vivian A
- Authors: Dalvit, Lorenzo , De Klerk, Vivian A
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6100 , http://hdl.handle.net/10962/d1008664
- Description: This article presents and discusses the results of a survey of a sample of Xhosa-speaking students at the University of Fort Hare regarding their attitudes towards the possible introduction of Xhosa as a medium of instruction at this institution. The research takes into account, among other things, the students' attitudes towards English and Xhosa and their opinions and beliefs about the introduction of dual-mediumship and its possible consequences. The survey was conducted with questionnaires and interviews and the results were first analysed as a whole, and then split into different categories according to gender, year of study, subject studied etc. This analysis indicates that while English is recognised as the dominant language in South Africa and, more specifically, in the domain of education, some categories of respondents acknowledge the usefulness of Xhosa as an additional medium of instruction. This survey clearly shows that it would make little sense to present Xhosa-speaking students at Fort Hare with a rigid choice between the existing English-medium and a dual-medium (English and Xhosa) policy and that more nuanced options would need to be offered. For example, respondents seem to consider the use of Xhosa as a medium of instruction more appropriate in the first years of study, for selected subjects and in some domains within the academic context rather than others. This study can be fruitfully compared with similar research carried out at other South African institutions. Moreover, the results of the present research can be used to inform future decisions regarding language policy at the University of Fort Hare.
- Full Text:
- Date Issued: 2005
- Authors: Dalvit, Lorenzo , De Klerk, Vivian A
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6100 , http://hdl.handle.net/10962/d1008664
- Description: This article presents and discusses the results of a survey of a sample of Xhosa-speaking students at the University of Fort Hare regarding their attitudes towards the possible introduction of Xhosa as a medium of instruction at this institution. The research takes into account, among other things, the students' attitudes towards English and Xhosa and their opinions and beliefs about the introduction of dual-mediumship and its possible consequences. The survey was conducted with questionnaires and interviews and the results were first analysed as a whole, and then split into different categories according to gender, year of study, subject studied etc. This analysis indicates that while English is recognised as the dominant language in South Africa and, more specifically, in the domain of education, some categories of respondents acknowledge the usefulness of Xhosa as an additional medium of instruction. This survey clearly shows that it would make little sense to present Xhosa-speaking students at Fort Hare with a rigid choice between the existing English-medium and a dual-medium (English and Xhosa) policy and that more nuanced options would need to be offered. For example, respondents seem to consider the use of Xhosa as a medium of instruction more appropriate in the first years of study, for selected subjects and in some domains within the academic context rather than others. This study can be fruitfully compared with similar research carried out at other South African institutions. Moreover, the results of the present research can be used to inform future decisions regarding language policy at the University of Fort Hare.
- Full Text:
- Date Issued: 2005
Energy versus angular momentum in black hole binaries
- Damour, T, Nagar, A, Pollney, D, Reisswig, C
- Authors: Damour, T , Nagar, A , Pollney, D , Reisswig, C
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6792 , http://hdl.handle.net/10962/d1006946
- Description: Using accurate numerical-relativity simulations of (nonspinning) black-hole binaries with mass ratios 1∶1, 2∶1, and 3∶1, we compute the gauge-invariant relation between the (reduced) binding energy E and the (reduced) angular momentum j of the system. We show that the relation E(j) is an accurate diagnostic of the dynamics of a black-hole binary in a highly relativistic regime. By comparing the numerical-relativity ENR(j) curve with the predictions of several analytic approximation schemes, we find that, while the canonically defined, nonresummed post-Newtonian–expanded EPN(j) relation exhibits large and growing deviations from ENR(j), the prediction of the effective one body formalism, based purely on known analytical results (without any calibration to numerical relativity), agrees strikingly well with the numerical-relativity results.
- Full Text:
- Date Issued: 2011
- Authors: Damour, T , Nagar, A , Pollney, D , Reisswig, C
- Date: 2011
- Language: English
- Type: Article
- Identifier: vital:6792 , http://hdl.handle.net/10962/d1006946
- Description: Using accurate numerical-relativity simulations of (nonspinning) black-hole binaries with mass ratios 1∶1, 2∶1, and 3∶1, we compute the gauge-invariant relation between the (reduced) binding energy E and the (reduced) angular momentum j of the system. We show that the relation E(j) is an accurate diagnostic of the dynamics of a black-hole binary in a highly relativistic regime. By comparing the numerical-relativity ENR(j) curve with the predictions of several analytic approximation schemes, we find that, while the canonically defined, nonresummed post-Newtonian–expanded EPN(j) relation exhibits large and growing deviations from ENR(j), the prediction of the effective one body formalism, based purely on known analytical results (without any calibration to numerical relativity), agrees strikingly well with the numerical-relativity results.
- Full Text:
- Date Issued: 2011
Nuclear translocation of the phosphoprotein Hop (Hsp70/Hsp90 organizing protein) occurs under heat shock, and its proposed nuclear localization signal is involved in Hsp90 binding
- Daniel, Sheril, Bradley, Graeme, Longshaw, Victoria M, Söti, Csaba, Csermely, Peter, Blatch, Gregory L
- Authors: Daniel, Sheril , Bradley, Graeme , Longshaw, Victoria M , Söti, Csaba , Csermely, Peter , Blatch, Gregory L
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6472 , http://hdl.handle.net/10962/d1005951 , http://dx.doi.org/10.1016/j.bbamcr.2008.01.014
- Description: The Hsp70–Hsp90 complex is implicated in the folding and regulation of numerous signaling proteins, and Hop, the Hsp70–Hsp90 Organizing Protein, facilitates the association of this multichaperone machinery. Phosphatase treatment of mouse cell extracts reduced the number of Hop isoforms compared to untreated extracts, providing the first direct evidence that Hop was phosphorylated in vivo. Furthermore, surface plasmon resonance (SPR) spectroscopy showed that a cdc2 kinase phosphorylation mimic of Hop had reduced affinity for Hsp90 binding. Hop was predominantly cytoplasmic, but translocated to the nucleus in response to heat shock. A putative bipartite nuclear localization signal (NLS) has been identified within the Hsp90-binding domain of Hop. Although substitution of residues within the major arm of this proposed NLS abolished Hop–Hsp90 interaction as determined by SPR, this was not sufficient to prevent the nuclear accumulation of Hop under leptomycin-B treatment and heat shock conditions. These results showed for the first time that the subcellular localization of Hop was stress regulated and that the major arm of the putative NLS was not directly important for nuclear translocation but was critical for Hop–Hsp90 association in vitro. We propose a model in which the association of Hop with Hsp90 and the phosphorylated status of Hop both play a role in the mechanism of nucleo-cytoplasmic shuttling of Hop.
- Full Text:
- Date Issued: 2008
- Authors: Daniel, Sheril , Bradley, Graeme , Longshaw, Victoria M , Söti, Csaba , Csermely, Peter , Blatch, Gregory L
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6472 , http://hdl.handle.net/10962/d1005951 , http://dx.doi.org/10.1016/j.bbamcr.2008.01.014
- Description: The Hsp70–Hsp90 complex is implicated in the folding and regulation of numerous signaling proteins, and Hop, the Hsp70–Hsp90 Organizing Protein, facilitates the association of this multichaperone machinery. Phosphatase treatment of mouse cell extracts reduced the number of Hop isoforms compared to untreated extracts, providing the first direct evidence that Hop was phosphorylated in vivo. Furthermore, surface plasmon resonance (SPR) spectroscopy showed that a cdc2 kinase phosphorylation mimic of Hop had reduced affinity for Hsp90 binding. Hop was predominantly cytoplasmic, but translocated to the nucleus in response to heat shock. A putative bipartite nuclear localization signal (NLS) has been identified within the Hsp90-binding domain of Hop. Although substitution of residues within the major arm of this proposed NLS abolished Hop–Hsp90 interaction as determined by SPR, this was not sufficient to prevent the nuclear accumulation of Hop under leptomycin-B treatment and heat shock conditions. These results showed for the first time that the subcellular localization of Hop was stress regulated and that the major arm of the putative NLS was not directly important for nuclear translocation but was critical for Hop–Hsp90 association in vitro. We propose a model in which the association of Hop with Hsp90 and the phosphorylated status of Hop both play a role in the mechanism of nucleo-cytoplasmic shuttling of Hop.
- Full Text:
- Date Issued: 2008
Pre-concentration of toxic metals using electrospun amino-functionalized nylon-6 nanofibre sorbent
- Darko, G, Sobola, A, Adewuyi, Sheriff, Okonkwo, J O, Torto, N
- Authors: Darko, G , Sobola, A , Adewuyi, Sheriff , Okonkwo, J O , Torto, N
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6571 , http://hdl.handle.net/10962/d1004134
- Description: This paper presents a new approach for pre-concentrating toxic metals (As, Cd, Ni and Pb) in aqueous environments using an amino-functionalized electrospun nanofibre sorbent. The sorbent, composed of nanofibres of average diameter 80 ± 10 nm and specific surface area of 58m2 g–1, exhibited fast adsorption kinetics (<20 min) for As, Cd, Ni and Pb. The optimalpHfor the uptake of As, Cd, Ni and Pb were 5.5, 6.0, 6.5 and 11, respectively. The adsorption process best fitted the Freundlich isothermand followed the first-order kinetics. The highest pre-concentration achieved using the sorbent was 41.99 (Ni in treated wastewater). The capacity of the sorbent to pre-concentrate the toxic metals was compared with those of aqua regia and HNO3+H2O2 digestions. The pre-concentration factors achieved for Cd in river water samples can be ranked as aqua regia digestion (0.73) > adsorption (0.34)>HNO3+H2O2 (0.23) digestion.Asimilar trend was observed for Ni in river water as well as Ni andCdin tap water samples. Pb ions in the river water samples were pre-concentrated slightly better using the two digestion methods pre-concentration factors ~22) compared to adsorption method (pre-concentration factor ~21). The use of the electrospun amino-functionalized nanofibre sorbent presentsanefficientand cost-effective alternative for pre-concentration of toxic metals inaqueousenvironments.
- Full Text:
- Date Issued: 2012
- Authors: Darko, G , Sobola, A , Adewuyi, Sheriff , Okonkwo, J O , Torto, N
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6571 , http://hdl.handle.net/10962/d1004134
- Description: This paper presents a new approach for pre-concentrating toxic metals (As, Cd, Ni and Pb) in aqueous environments using an amino-functionalized electrospun nanofibre sorbent. The sorbent, composed of nanofibres of average diameter 80 ± 10 nm and specific surface area of 58m2 g–1, exhibited fast adsorption kinetics (<20 min) for As, Cd, Ni and Pb. The optimalpHfor the uptake of As, Cd, Ni and Pb were 5.5, 6.0, 6.5 and 11, respectively. The adsorption process best fitted the Freundlich isothermand followed the first-order kinetics. The highest pre-concentration achieved using the sorbent was 41.99 (Ni in treated wastewater). The capacity of the sorbent to pre-concentrate the toxic metals was compared with those of aqua regia and HNO3+H2O2 digestions. The pre-concentration factors achieved for Cd in river water samples can be ranked as aqua regia digestion (0.73) > adsorption (0.34)>HNO3+H2O2 (0.23) digestion.Asimilar trend was observed for Ni in river water as well as Ni andCdin tap water samples. Pb ions in the river water samples were pre-concentrated slightly better using the two digestion methods pre-concentration factors ~22) compared to adsorption method (pre-concentration factor ~21). The use of the electrospun amino-functionalized nanofibre sorbent presentsanefficientand cost-effective alternative for pre-concentration of toxic metals inaqueousenvironments.
- Full Text:
- Date Issued: 2012
Municipal commonage policy and livestock owners : findings from the Eastern Cape, South Africa
- Davenport, Nicholas A, Gambiza, James
- Authors: Davenport, Nicholas A , Gambiza, James
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6628 , http://hdl.handle.net/10962/d1006820
- Description: The new African National Congress government announced after 1994 that municipal commonage would be a pillar of their land reform programme. The Department of Land Affairs spearheaded this by acquiring new land to complement the existing ‘old’ commonages. The aim of old commonage was to supplement the income of poor urban residents through the subsistence user system whereas new commonage was intended as a ‘stepping stone’ for emergent farmers. We investigated the differences between old and new commonage farmers as well as how they perceived the Makana local municipality's capacity to manage the commonage. The results showed that local institutions were weak. Only 46% of the old commonage farmers were members of a local livestock association whereas 74% of the new commonage farmers were members. Most old commonage farmers (59%) were dissatisfied with local government's management of the commonage. In contrast, only 37% of the new commonage farmers were dissatisfied with the management of the commonage. There were no differences between old and new commonage farmers in terms of livestock owners’ characteristics and mean annual net direct-use value of livestock. There were also no differences in the age of the two types of commonage farmers. Furthermore, there was no association between the type of commonage and level of education. The mean annual net direct-use value of livestock on old commonage was R6308 compared with R9707 on new commonage. Although the income from livestock for new commonage farmers varied slightly from that of old commonage farmers, the annual productive output per farmer on old commonage was R473 ha−1, three times higher than that of new commonage farmers which was R134 ha−1. We suggest that new land policy legislation is needed in which poverty as well as the legal arrangements between all stakeholders is clearly defined. Furthermore, national departments need to be more involved with local municipalities to increase local management capacity.
- Full Text:
- Date Issued: 2009
- Authors: Davenport, Nicholas A , Gambiza, James
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6628 , http://hdl.handle.net/10962/d1006820
- Description: The new African National Congress government announced after 1994 that municipal commonage would be a pillar of their land reform programme. The Department of Land Affairs spearheaded this by acquiring new land to complement the existing ‘old’ commonages. The aim of old commonage was to supplement the income of poor urban residents through the subsistence user system whereas new commonage was intended as a ‘stepping stone’ for emergent farmers. We investigated the differences between old and new commonage farmers as well as how they perceived the Makana local municipality's capacity to manage the commonage. The results showed that local institutions were weak. Only 46% of the old commonage farmers were members of a local livestock association whereas 74% of the new commonage farmers were members. Most old commonage farmers (59%) were dissatisfied with local government's management of the commonage. In contrast, only 37% of the new commonage farmers were dissatisfied with the management of the commonage. There were no differences between old and new commonage farmers in terms of livestock owners’ characteristics and mean annual net direct-use value of livestock. There were also no differences in the age of the two types of commonage farmers. Furthermore, there was no association between the type of commonage and level of education. The mean annual net direct-use value of livestock on old commonage was R6308 compared with R9707 on new commonage. Although the income from livestock for new commonage farmers varied slightly from that of old commonage farmers, the annual productive output per farmer on old commonage was R473 ha−1, three times higher than that of new commonage farmers which was R134 ha−1. We suggest that new land policy legislation is needed in which poverty as well as the legal arrangements between all stakeholders is clearly defined. Furthermore, national departments need to be more involved with local municipalities to increase local management capacity.
- Full Text:
- Date Issued: 2009
Ten years of marine natural products research at Rhodes University
- Davies-Coleman, Michael T, Beukes, Denzil R
- Authors: Davies-Coleman, Michael T , Beukes, Denzil R
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6568 , http://hdl.handle.net/10962/d1004131
- Description: Marine invertebrates, algae and microorganisms produce a plethora of structurally unique and biologically active secondary metabolites. The ecological roles of these natural products, although not completely understood, range from chemical defence against predation to intra-specific cues for larval settlement. Surprisingly, a number of these metabolites have also shown potential as new medicines for the treatment of a variety of diseases including cancer. The natural products chemistry of southern Africa’s unique marine flora and fauna is relatively unknown and this review provides an overview of the contribution made by the marine natural products research group at Rhodes University to the isolation, identification and synthesis of biologically active natural products from southern African marine microorganisms, algae, sponges, ascidians, soft corals and molluscs.
- Full Text:
- Date Issued: 2004
- Authors: Davies-Coleman, Michael T , Beukes, Denzil R
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6568 , http://hdl.handle.net/10962/d1004131
- Description: Marine invertebrates, algae and microorganisms produce a plethora of structurally unique and biologically active secondary metabolites. The ecological roles of these natural products, although not completely understood, range from chemical defence against predation to intra-specific cues for larval settlement. Surprisingly, a number of these metabolites have also shown potential as new medicines for the treatment of a variety of diseases including cancer. The natural products chemistry of southern Africa’s unique marine flora and fauna is relatively unknown and this review provides an overview of the contribution made by the marine natural products research group at Rhodes University to the isolation, identification and synthesis of biologically active natural products from southern African marine microorganisms, algae, sponges, ascidians, soft corals and molluscs.
- Full Text:
- Date Issued: 2004