A preliminary survey of the estuaries on the south coast of South Africa, Cape St Blaize, Mossel Bay - Robberg Peninsula, Plettenberg Bay, with particular reference to the fish fauna
- James, Nicola Caroline, Harrison, T D
- Authors: James, Nicola Caroline , Harrison, T D
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:7141 , http://hdl.handle.net/10962/d1011834
- Description: The coastal river systems on the south coast of South Africa from Cape St Blaize to Robberg Peninsula were surveyed during October and November 1994. The ichthyofaunal and physico-chemical characteristics of each system are presented and their suitability as estuarine nursery areas is discussed. Five systems (Rooi, Meul, Grooteiland, Kranshoek and Crooks) are outlets of small coastal streams and probably provide little or no habitat for either resident estuarine or migrant marine fishes owing to their small size. Four systems (Maalgate, Gwaing, Skaapkop and Kaaimans) are located within deeply incised valleys and have a permanent connection with the sea. The amount of marginal and intertidal habitat available to fishes, however, is limited due to their morphology. Six systems (Hartenbos, Groot Brak, Touw, Swartvlei, Goukamma and Noetsie) are intermittently open to the sea. Although the Touw and Swartvlei are connected to coastal lake systems, flow within these estuaries is not sufficient to prevent the build up of a sand barrier at the mouth. The Hartenbos, Groot Brak, Goukamma, and Noetsie are also periodically closed by a sand bar. The construction of a dam in the lower catchment of the Groot Brak has affected the hydrology of the system. The two remaining estuaries (Klein Brak and Knysna) are permanently open. In addition to strong tidal currents, the fixing of the mouth of the Knysna Estuary between rocky headlands also serves to maintain a permanent connection with the sea. Mugilidae and Sparidae were represented by the greatest number of species, and also dominated catches numerically and by mass. The fish fauna of all the estuaries surveyed were dominated by the juveniles of estuarine-dependent marine species and estuarine-resident species were also well represented in catches. The estuaries surveyed provide a vital habitat for both marine migrant species and resident species, most of which are endemic to the region.
- Full Text:
- Date Issued: 2008
- Authors: James, Nicola Caroline , Harrison, T D
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:7141 , http://hdl.handle.net/10962/d1011834
- Description: The coastal river systems on the south coast of South Africa from Cape St Blaize to Robberg Peninsula were surveyed during October and November 1994. The ichthyofaunal and physico-chemical characteristics of each system are presented and their suitability as estuarine nursery areas is discussed. Five systems (Rooi, Meul, Grooteiland, Kranshoek and Crooks) are outlets of small coastal streams and probably provide little or no habitat for either resident estuarine or migrant marine fishes owing to their small size. Four systems (Maalgate, Gwaing, Skaapkop and Kaaimans) are located within deeply incised valleys and have a permanent connection with the sea. The amount of marginal and intertidal habitat available to fishes, however, is limited due to their morphology. Six systems (Hartenbos, Groot Brak, Touw, Swartvlei, Goukamma and Noetsie) are intermittently open to the sea. Although the Touw and Swartvlei are connected to coastal lake systems, flow within these estuaries is not sufficient to prevent the build up of a sand barrier at the mouth. The Hartenbos, Groot Brak, Goukamma, and Noetsie are also periodically closed by a sand bar. The construction of a dam in the lower catchment of the Groot Brak has affected the hydrology of the system. The two remaining estuaries (Klein Brak and Knysna) are permanently open. In addition to strong tidal currents, the fixing of the mouth of the Knysna Estuary between rocky headlands also serves to maintain a permanent connection with the sea. Mugilidae and Sparidae were represented by the greatest number of species, and also dominated catches numerically and by mass. The fish fauna of all the estuaries surveyed were dominated by the juveniles of estuarine-dependent marine species and estuarine-resident species were also well represented in catches. The estuaries surveyed provide a vital habitat for both marine migrant species and resident species, most of which are endemic to the region.
- Full Text:
- Date Issued: 2008
Chieftainship in Transkeian political development
- Authors: Hammond-Tooke, W D
- Date: 1964
- Language: English
- Type: Article
- Identifier: vital:6113 , http://hdl.handle.net/10962/d1003835
- Description: In November 1963 the inhabitants of the Transkeian Territories, the largest block of Bantu reserve in the Republic of South Africa, went to the polls to elect representatives for a Legislative Assembly, upon whom the responsibility for the government of this, the first so-called ‘Bantustan’ to achieve a limited form of self-government, is to be laid. The election was the culminating point in a series of changes in the administrative structure of the area which have been characterized by an emphasis on the institution of chieftainship as the basis of local government. After approximately 60 years of rule through magistrates (later supplemented by a system of district councils) the Bantu Authorities Act of 1955 was introduced, giving greatly enhanced powers to the Chiefs, who now became the heads of the tribally-structured Bantu Authorities.
- Full Text:
- Date Issued: 1964
- Authors: Hammond-Tooke, W D
- Date: 1964
- Language: English
- Type: Article
- Identifier: vital:6113 , http://hdl.handle.net/10962/d1003835
- Description: In November 1963 the inhabitants of the Transkeian Territories, the largest block of Bantu reserve in the Republic of South Africa, went to the polls to elect representatives for a Legislative Assembly, upon whom the responsibility for the government of this, the first so-called ‘Bantustan’ to achieve a limited form of self-government, is to be laid. The election was the culminating point in a series of changes in the administrative structure of the area which have been characterized by an emphasis on the institution of chieftainship as the basis of local government. After approximately 60 years of rule through magistrates (later supplemented by a system of district councils) the Bantu Authorities Act of 1955 was introduced, giving greatly enhanced powers to the Chiefs, who now became the heads of the tribally-structured Bantu Authorities.
- Full Text:
- Date Issued: 1964
Development of a regional GPS-based ionospheric TEC model for South Africa
- Opperman, Ben D L, Cilliers, Pierre J, McKinnell, Lee-Anne, Haggard, Raymond
- Authors: Opperman, Ben D L , Cilliers, Pierre J , McKinnell, Lee-Anne , Haggard, Raymond
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6799 , http://hdl.handle.net/10962/d1003925
- Description: Advances in South African space physics research and related disciplines require better spatial and time resolution ionospheric information than was previously possible with the existing ionosonde network. A GPS-based, variable degree adjusted spherical harmonic (ASHA) model was developed for near real-time regional ionospheric total electron content (TEC) mapping over South Africa. Slant TEC values along oblique GPS signal paths are quantified from a network of GPS receivers and converted to vertical TEC by means of the single layer mapping function. The ASHA model coefficients and GPS differential biases are estimated from vertical TEC at the ionospheric pierce points and used to interpolate TEC at any location within the region of interest. Diurnal TEC variations with one minute time resolution and time-varying 2D regional TEC maps are constructed. In order to validate the ASHA method, simulations with an IRI ionosphere were performed, while the ASHA results from actual data were compared with two independent GPS-based methodologies and measured ionosonde data.
- Full Text:
- Date Issued: 2007
- Authors: Opperman, Ben D L , Cilliers, Pierre J , McKinnell, Lee-Anne , Haggard, Raymond
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6799 , http://hdl.handle.net/10962/d1003925
- Description: Advances in South African space physics research and related disciplines require better spatial and time resolution ionospheric information than was previously possible with the existing ionosonde network. A GPS-based, variable degree adjusted spherical harmonic (ASHA) model was developed for near real-time regional ionospheric total electron content (TEC) mapping over South Africa. Slant TEC values along oblique GPS signal paths are quantified from a network of GPS receivers and converted to vertical TEC by means of the single layer mapping function. The ASHA model coefficients and GPS differential biases are estimated from vertical TEC at the ionospheric pierce points and used to interpolate TEC at any location within the region of interest. Diurnal TEC variations with one minute time resolution and time-varying 2D regional TEC maps are constructed. In order to validate the ASHA method, simulations with an IRI ionosphere were performed, while the ASHA results from actual data were compared with two independent GPS-based methodologies and measured ionosonde data.
- Full Text:
- Date Issued: 2007
Electrocatalysis of asulam on cobalt phthalocyanine modified multi-walled carbon nanotubes immobilized on a basal plane pyrolytic graphite electrode
- Siswana, Msimelelo P, Ozoemena, Kenneth I, Nyokong, Tebello
- Authors: Siswana, Msimelelo P , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6595 , http://hdl.handle.net/10962/d1004344
- Description: This work describes the electrochemical properties of cobalt tetra-aminophthalocyanine (CoTAPc) complex electropolymerized at the surface of multi-walled carbon nanotube (MWCNT) abrasively immobilized onto a basal plane pyrolytic graphite electrode (BPPGE). The constructed electrode displayed excellent electrocatalytic behaviour towards the oxidation of the herbicide, asulam, as evidenced by the enhancement of the oxidation peak current (~6 times) and the shift in the oxidation potential to lower values (by ~120 mV) in comparison with the bare BPPGE. The chronoamperometric detection of asulam which was carried out in 0.10 M phosphate buffer (pH 7.0) at a fixed potential of 0.65 V (versus Ag|AgCl) yielded excellent analytical parameters; a linear concentration range of 4.5–20 μM, a sensitivity of 241 × 10[superscript −3] μA/μM, a detection limit of 1.15 μM asulam (using the Y[subscript B] + 3σ criterion) and a response time of ~2 s.
- Full Text:
- Date Issued: 2006
- Authors: Siswana, Msimelelo P , Ozoemena, Kenneth I , Nyokong, Tebello
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6595 , http://hdl.handle.net/10962/d1004344
- Description: This work describes the electrochemical properties of cobalt tetra-aminophthalocyanine (CoTAPc) complex electropolymerized at the surface of multi-walled carbon nanotube (MWCNT) abrasively immobilized onto a basal plane pyrolytic graphite electrode (BPPGE). The constructed electrode displayed excellent electrocatalytic behaviour towards the oxidation of the herbicide, asulam, as evidenced by the enhancement of the oxidation peak current (~6 times) and the shift in the oxidation potential to lower values (by ~120 mV) in comparison with the bare BPPGE. The chronoamperometric detection of asulam which was carried out in 0.10 M phosphate buffer (pH 7.0) at a fixed potential of 0.65 V (versus Ag|AgCl) yielded excellent analytical parameters; a linear concentration range of 4.5–20 μM, a sensitivity of 241 × 10[superscript −3] μA/μM, a detection limit of 1.15 μM asulam (using the Y[subscript B] + 3σ criterion) and a response time of ~2 s.
- Full Text:
- Date Issued: 2006
Evaluating the IRI topside model for the South African region: An overview of the modelling techniques
- Sibanda, Patrick, McKinnell, Lee-Anne
- Authors: Sibanda, Patrick , McKinnell, Lee-Anne
- Date: 2009
- Language: English
- Type: text , Article
- Identifier: vital:6810 , http://hdl.handle.net/10962/d1004303
- Description: The representation of the topside ionosphere (the region above the F2 peak) is critical because of the limited experimental data available. Over the years, a wide range of models have been developed in an effort to represent the behaviour and the shape of the electron density (Ne) profile of the topside ionosphere. Various studies have been centred around calculating the vertical scale height (VSH) and have included (a) obtaining VSH from Global Positioning System (GPS) derived total electron content (TEC), (b) calculating the VSH from ground-based ionosonde measurements, (c) using topside sounder vertical Ne profiles to obtain the VSH. One or a combination of the topside profilers (Chapman function, exponential function, sech-squared (Epstein) function, and/or parabolic function) is then used to reconstruct the topside Ne profile. The different approaches and the modelling techniques are discussed with a view to identifying the most adequate approach to apply to the South African region’s topside modelling efforts. The IRI-2001 topside model is evaluated based on how well it reproduces measured topside profiles over the South African region. This study is a first step in the process of developing a South African topside ionosphere model.
- Full Text:
- Date Issued: 2009
- Authors: Sibanda, Patrick , McKinnell, Lee-Anne
- Date: 2009
- Language: English
- Type: text , Article
- Identifier: vital:6810 , http://hdl.handle.net/10962/d1004303
- Description: The representation of the topside ionosphere (the region above the F2 peak) is critical because of the limited experimental data available. Over the years, a wide range of models have been developed in an effort to represent the behaviour and the shape of the electron density (Ne) profile of the topside ionosphere. Various studies have been centred around calculating the vertical scale height (VSH) and have included (a) obtaining VSH from Global Positioning System (GPS) derived total electron content (TEC), (b) calculating the VSH from ground-based ionosonde measurements, (c) using topside sounder vertical Ne profiles to obtain the VSH. One or a combination of the topside profilers (Chapman function, exponential function, sech-squared (Epstein) function, and/or parabolic function) is then used to reconstruct the topside Ne profile. The different approaches and the modelling techniques are discussed with a view to identifying the most adequate approach to apply to the South African region’s topside modelling efforts. The IRI-2001 topside model is evaluated based on how well it reproduces measured topside profiles over the South African region. This study is a first step in the process of developing a South African topside ionosphere model.
- Full Text:
- Date Issued: 2009
Fishes of the deep demersal habitat at Ngazidja (Grand Comoro) Island, Western Indian Ocean
- Heemstra, P C, Hissmann, K, Fricke, H
- Authors: Heemstra, P C , Hissmann, K , Fricke, H
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7128 , http://hdl.handle.net/10962/d1010638
- Description: Underwater observations of the coelacanth, Latimeria chalumnae Smith, 1939, from a research submersible provided opportunities to study the deep demersal fish fauna at the Comoro Islands. The demersal habitat in depths of 150–400 m at the volcanic island of Ngazidja is low in fish diversity and biomass, compared with the shallow-water coral reef habitat of Ngazidja or the deep demersal habitats of other localities in the Indo-Pacific region. The resident deep demersal fish fauna at Ngazidja is dominated by the coelacanth, an ancient predator that is specially adapted for this low-energy environment. Other large fish predators are scarce in this environment, because of the heavy fishing pressure from local fishermen. Eighty-nine fish taxa (including 65 recognizable species) were recorded from videotapes, photographs, visual observations, fishermen’s catches and ancillary attempts to sample the fish fauna with baited fish traps, gill nets, and hook and line. Although no coelacanth feeding events were seen, seven fish species are known from coelacanth stomach contents, and 64 other fish species in this habitat are considered potential prey of this dominant predator.
- Full Text:
- Date Issued: 2006
- Authors: Heemstra, P C , Hissmann, K , Fricke, H
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7128 , http://hdl.handle.net/10962/d1010638
- Description: Underwater observations of the coelacanth, Latimeria chalumnae Smith, 1939, from a research submersible provided opportunities to study the deep demersal fish fauna at the Comoro Islands. The demersal habitat in depths of 150–400 m at the volcanic island of Ngazidja is low in fish diversity and biomass, compared with the shallow-water coral reef habitat of Ngazidja or the deep demersal habitats of other localities in the Indo-Pacific region. The resident deep demersal fish fauna at Ngazidja is dominated by the coelacanth, an ancient predator that is specially adapted for this low-energy environment. Other large fish predators are scarce in this environment, because of the heavy fishing pressure from local fishermen. Eighty-nine fish taxa (including 65 recognizable species) were recorded from videotapes, photographs, visual observations, fishermen’s catches and ancillary attempts to sample the fish fauna with baited fish traps, gill nets, and hook and line. Although no coelacanth feeding events were seen, seven fish species are known from coelacanth stomach contents, and 64 other fish species in this habitat are considered potential prey of this dominant predator.
- Full Text:
- Date Issued: 2006
Fishes of the deep demersal habitat at Ngazidja (Grand Comoro) Island, Western Indian Ocean
- Heemstra, P C, Hissmann, K, Fricke, H
- Authors: Heemstra, P C , Hissmann, K , Fricke, H
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7158 , http://hdl.handle.net/10962/d1011885
- Description: Underwater observations of the coelacanth, Latimeria chalumnae Smith, 1939, from a research submersible provided opportunities to study the deep demersal fish fauna at the Comoro Islands. The demersal habitat in depths of 150–400 m at the volcanic island of Ngazidja is low in fish diversity and biomass, compared with the shallow-water coral reef habitat of Ngazidja or the deep demersal habitats of other localities in the Indo-Pacific region. The resident deep demersal fish fauna at Ngazidja is dominated by the coelacanth, an ancient predator that is specially adapted for this low-energy environment. Other large fish predators are scarce in this environment, because of the heavy fishing pressure from local fishermen. Eighty-nine fish taxa (including 65 recognizable species) were recorded from videotapes, photographs, visual observations, fishermen’s catches and ancillary attempts to sample the fish fauna with baited fish traps, gill nets, and hook and line. Although no coelacanth feeding events were seen, seven fish species are known from coelacanth stomach contents, and 64 other fish species in this habitat are considered potential prey of this dominant predator.
- Full Text:
- Date Issued: 2006
- Authors: Heemstra, P C , Hissmann, K , Fricke, H
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7158 , http://hdl.handle.net/10962/d1011885
- Description: Underwater observations of the coelacanth, Latimeria chalumnae Smith, 1939, from a research submersible provided opportunities to study the deep demersal fish fauna at the Comoro Islands. The demersal habitat in depths of 150–400 m at the volcanic island of Ngazidja is low in fish diversity and biomass, compared with the shallow-water coral reef habitat of Ngazidja or the deep demersal habitats of other localities in the Indo-Pacific region. The resident deep demersal fish fauna at Ngazidja is dominated by the coelacanth, an ancient predator that is specially adapted for this low-energy environment. Other large fish predators are scarce in this environment, because of the heavy fishing pressure from local fishermen. Eighty-nine fish taxa (including 65 recognizable species) were recorded from videotapes, photographs, visual observations, fishermen’s catches and ancillary attempts to sample the fish fauna with baited fish traps, gill nets, and hook and line. Although no coelacanth feeding events were seen, seven fish species are known from coelacanth stomach contents, and 64 other fish species in this habitat are considered potential prey of this dominant predator.
- Full Text:
- Date Issued: 2006
Fuelwood harvesting and selection in Valley Thicket, South Africa
- Pote, J, Shackleton, Charlie M, Cocks, Michelle L, Lubke, Roy
- Authors: Pote, J , Shackleton, Charlie M , Cocks, Michelle L , Lubke, Roy
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6531 , http://hdl.handle.net/10962/d1005972
- Description: The Thicket Biome is the second smallest biome in South Africa, and is renowned for its high biodiversity. Yet, less than 5% of the biome is in formal conservation areas. Much of the currently intact thicket outside protected areas is threatened by land transformation to commercial agriculture or heavy use by rural communities. There is limited understanding of the ecological structure and function of thicket communities and their response to these human pressures. This paper reports on a study to characterize the woody communities in Valley Thicket and Thornveld surrounding a rural village. We also examined the demand and selection for specific woody species. There was a marked selection for key species for different uses, including fuelwood, construction timber, and cultural stacks. There was also strong selection for specific size classes of stem, especially those between 16–45 cm circumference. The density, biomass and species richness of woody species was reduced close to the village, and increased with distance away from human settlement. A similar trend was found for the basal area of preferred species, but not for the basal area of all species. The strong selectivity for both species and size class means that the anthropogenic impacts are not uniform within the woody strata, leading to marked changes in community structure and floristics at a local scale.
- Full Text:
- Date Issued: 2006
- Authors: Pote, J , Shackleton, Charlie M , Cocks, Michelle L , Lubke, Roy
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6531 , http://hdl.handle.net/10962/d1005972
- Description: The Thicket Biome is the second smallest biome in South Africa, and is renowned for its high biodiversity. Yet, less than 5% of the biome is in formal conservation areas. Much of the currently intact thicket outside protected areas is threatened by land transformation to commercial agriculture or heavy use by rural communities. There is limited understanding of the ecological structure and function of thicket communities and their response to these human pressures. This paper reports on a study to characterize the woody communities in Valley Thicket and Thornveld surrounding a rural village. We also examined the demand and selection for specific woody species. There was a marked selection for key species for different uses, including fuelwood, construction timber, and cultural stacks. There was also strong selection for specific size classes of stem, especially those between 16–45 cm circumference. The density, biomass and species richness of woody species was reduced close to the village, and increased with distance away from human settlement. A similar trend was found for the basal area of preferred species, but not for the basal area of all species. The strong selectivity for both species and size class means that the anthropogenic impacts are not uniform within the woody strata, leading to marked changes in community structure and floristics at a local scale.
- Full Text:
- Date Issued: 2006
Global diversity of mayflies (Ephemeroptera, Insecta) in freshwater
- Barber-James, Helen M, Gattolliat, J-L, Sartori, Michel, Hubbard, Michael D
- Authors: Barber-James, Helen M , Gattolliat, J-L , Sartori, Michel , Hubbard, Michael D
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6895 , http://hdl.handle.net/10962/d1011655
- Description: The extant global Ephemeroptera fauna is represented by over 3,000 described species in 42 families and more than 400 genera. The highest generic diversity occurs in the Neotropics, with a correspondingly high species diversity, while the Palaearctic has the lowest generic diversity, but a high species diversity. Such distribution patterns may relate to how long evolutionary processes have been carrying on in isolation in a bioregion. Over an extended period, there may be extinction of species, but evolution of more genera. Dramatic extinction events such as the K-T mass extinction have affected current mayfly diversity and distribution. Climatic history plays an important role in the rate of speciation in an area, with regions which have been climatically stable over long periods having fewer species per genus, when compared to regions subjected to climatic stresses, such as glaciation. A total of 13 families are endemic to specific bioregions, with eight among them being monospecific. Most of these have restricted distributions which may be the result of them being the relict of a previously more diverse, but presently almost completely extinct family, or may be the consequence of vicariance events, resulting from evolution due to long-term isolation.
- Full Text:
- Date Issued: 2008
- Authors: Barber-James, Helen M , Gattolliat, J-L , Sartori, Michel , Hubbard, Michael D
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6895 , http://hdl.handle.net/10962/d1011655
- Description: The extant global Ephemeroptera fauna is represented by over 3,000 described species in 42 families and more than 400 genera. The highest generic diversity occurs in the Neotropics, with a correspondingly high species diversity, while the Palaearctic has the lowest generic diversity, but a high species diversity. Such distribution patterns may relate to how long evolutionary processes have been carrying on in isolation in a bioregion. Over an extended period, there may be extinction of species, but evolution of more genera. Dramatic extinction events such as the K-T mass extinction have affected current mayfly diversity and distribution. Climatic history plays an important role in the rate of speciation in an area, with regions which have been climatically stable over long periods having fewer species per genus, when compared to regions subjected to climatic stresses, such as glaciation. A total of 13 families are endemic to specific bioregions, with eight among them being monospecific. Most of these have restricted distributions which may be the result of them being the relict of a previously more diverse, but presently almost completely extinct family, or may be the consequence of vicariance events, resulting from evolution due to long-term isolation.
- Full Text:
- Date Issued: 2008
Global diversity of mayflies (Ephemeroptera, Insecta) in freshwater
- Barber-James, Helen M, Gattolliat, Jean-Luc, Sartori, Michel, Hubbard, Michael D
- Authors: Barber-James, Helen M , Gattolliat, Jean-Luc , Sartori, Michel , Hubbard, Michael D
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:7002 , http://hdl.handle.net/10962/d1008361
- Description: The extant global Ephemeroptera fauna is represented by over 3,000 described species in 42 families and more than 400 genera. The highest generic diversity occurs in the Neotropics, with a correspondingly high species diversity, while the Palaearctic has the lowest generic diversity, but a high species diversity. Such distribution patterns may relate to how long evolutionary processes have been carrying on in isolation in a bioregion. Over an extended period, there may be extinction of species, but evolution of more genera. Dramatic extinction events such as the K-T mass extinction have affected current mayfly diversity and distribution. Climatic history plays an important role in the rate of speciation in an area, with regions which have been climatically stable over long periods having fewer species per genus, when compared to regions subjected to climatic stresses, such as glaciation. A total of 13 families are endemic to specific bioregions, with eight among them being monospecific. Most of these have restricted distributions which may be the result of them being the relict of a previously more diverse, but presently almost completely extinct family, or may be the consequence of vicariance events, resulting from evolution due to long-term isolation.
- Full Text:
- Date Issued: 2007
- Authors: Barber-James, Helen M , Gattolliat, Jean-Luc , Sartori, Michel , Hubbard, Michael D
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:7002 , http://hdl.handle.net/10962/d1008361
- Description: The extant global Ephemeroptera fauna is represented by over 3,000 described species in 42 families and more than 400 genera. The highest generic diversity occurs in the Neotropics, with a correspondingly high species diversity, while the Palaearctic has the lowest generic diversity, but a high species diversity. Such distribution patterns may relate to how long evolutionary processes have been carrying on in isolation in a bioregion. Over an extended period, there may be extinction of species, but evolution of more genera. Dramatic extinction events such as the K-T mass extinction have affected current mayfly diversity and distribution. Climatic history plays an important role in the rate of speciation in an area, with regions which have been climatically stable over long periods having fewer species per genus, when compared to regions subjected to climatic stresses, such as glaciation. A total of 13 families are endemic to specific bioregions, with eight among them being monospecific. Most of these have restricted distributions which may be the result of them being the relict of a previously more diverse, but presently almost completely extinct family, or may be the consequence of vicariance events, resulting from evolution due to long-term isolation.
- Full Text:
- Date Issued: 2007
Nicknames as sex-role stereotypes
- De Klerk, Vivian A, Bosch, Agnes Barbara
- Authors: De Klerk, Vivian A , Bosch, Agnes Barbara
- Date: 1996
- Language: English
- Type: Article
- Identifier: vital:6134 , http://hdl.handle.net/10962/d1011586
- Description: Nicknames are powerful indicators of attitudes towards gender categories and because of their transient and optional nature, it has been argued that they are more likely to show a closer relationship to ongoing trends in the culture and society than other more fixed parts of the language E. B. Phillips (1990) ["Nicknames and Sex Role Stereotypes," Sex Roles, Vol. 23, pp. 281-289]. This study reports on a survey of nickname usage among a group of South African adolescents from mixed socioeconomic backgrounds (approximately 25% other than white) in an attempt to explicate gender-linked trends in frequency of occurrence, usage and attitudes to such special names. It reveals that conventions regarding nickname coinage and usage are intimately connected to the gender of bearers and users, and that more males have nicknames and coin them than females; it also shows significant sex-linked differences in the linguistic sources and users of nicknames, and reveals a greater tendency for female nicknames to function as indicators of affection rather than for humorous or critical effect. It could be argued that these trends could be linked to the nurturing and nurtured role of females in society, and to the differences in social power generally between males and females.
- Full Text:
- Date Issued: 1996
- Authors: De Klerk, Vivian A , Bosch, Agnes Barbara
- Date: 1996
- Language: English
- Type: Article
- Identifier: vital:6134 , http://hdl.handle.net/10962/d1011586
- Description: Nicknames are powerful indicators of attitudes towards gender categories and because of their transient and optional nature, it has been argued that they are more likely to show a closer relationship to ongoing trends in the culture and society than other more fixed parts of the language E. B. Phillips (1990) ["Nicknames and Sex Role Stereotypes," Sex Roles, Vol. 23, pp. 281-289]. This study reports on a survey of nickname usage among a group of South African adolescents from mixed socioeconomic backgrounds (approximately 25% other than white) in an attempt to explicate gender-linked trends in frequency of occurrence, usage and attitudes to such special names. It reveals that conventions regarding nickname coinage and usage are intimately connected to the gender of bearers and users, and that more males have nicknames and coin them than females; it also shows significant sex-linked differences in the linguistic sources and users of nicknames, and reveals a greater tendency for female nicknames to function as indicators of affection rather than for humorous or critical effect. It could be argued that these trends could be linked to the nurturing and nurtured role of females in society, and to the differences in social power generally between males and females.
- Full Text:
- Date Issued: 1996
Olive Schreiner in Rhodesia: an episode in a biography
- Walters, Paul S, Fogg, W Jeremy M
- Authors: Walters, Paul S , Fogg, W Jeremy M
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6123 , http://hdl.handle.net/10962/d1004707
- Description: Readers of biographies of Olive Schreiner - except for the pioneering work of Vera Buchanan-Gould (see 1948, 198-99) - could be forgiven for doubting whether Olive Schreiner ever was in Rhodesia. Although her husband's edition of her Letters includes three which cover this journey (Cronwright-Schreiner 1924a), he makes no mention of it in his Life (1924), and it is not touched on either in First and Scott (1980) or in Stanley's impressive biographical chapter (2002). Arguably, it does nothing to alter the by now well-established outlines of Olive Schreiner's life; yet, as we shall see, the visit itself might have meant the premature end of that life. Moreover, it documents Schreiner's visit to two sites of immense importance to her : the 'Hanging Tree' in Bulawayo which features in the (deliberately shocking) photographic frontispiece to the first edition of Trooper Peter Halket of Mashonaland (1897), and, secondly, Cecil Rhodes's grave in the Matopos. In just over a decade (13 Aug. 1921), she too would lie in her chosen mountaintop tomb.
- Full Text:
- Date Issued: 2007
- Authors: Walters, Paul S , Fogg, W Jeremy M
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6123 , http://hdl.handle.net/10962/d1004707
- Description: Readers of biographies of Olive Schreiner - except for the pioneering work of Vera Buchanan-Gould (see 1948, 198-99) - could be forgiven for doubting whether Olive Schreiner ever was in Rhodesia. Although her husband's edition of her Letters includes three which cover this journey (Cronwright-Schreiner 1924a), he makes no mention of it in his Life (1924), and it is not touched on either in First and Scott (1980) or in Stanley's impressive biographical chapter (2002). Arguably, it does nothing to alter the by now well-established outlines of Olive Schreiner's life; yet, as we shall see, the visit itself might have meant the premature end of that life. Moreover, it documents Schreiner's visit to two sites of immense importance to her : the 'Hanging Tree' in Bulawayo which features in the (deliberately shocking) photographic frontispiece to the first edition of Trooper Peter Halket of Mashonaland (1897), and, secondly, Cecil Rhodes's grave in the Matopos. In just over a decade (13 Aug. 1921), she too would lie in her chosen mountaintop tomb.
- Full Text:
- Date Issued: 2007
Optimization of salbutamol sulfate dissolution from sustained release matrix formulations using an artificial neural network
- Chaibva, Faith A, Burton, Michael, Walker, Roderick B
- Authors: Chaibva, Faith A , Burton, Michael , Walker, Roderick B
- Date: 2010
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Article
- Identifier: vital:6352 , http://hdl.handle.net/10962/d1006034
- Description: An artificial neural network was used to optimize the release of salbutamol sulfate from hydrophilic matrix formulations. Model formulations to be used for training, testing and validating the neural network were manufactured with the aid of a central composite design with varying the levels of Methocel® K100M, xanthan gum, Carbopol® 974P and Surelease® as the input factors. In vitro dissolution time profiles at six different sampling times were used as target data in training the neural network for formulation optimization. A multi layer perceptron with one hidden layer was constructed using Matlab®, and the number of nodes in the hidden layer was optimized by trial and error to develop a model with the best predictive ability. The results revealed that a neural network with nine nodes was optimal for developing and optimizing formulations. Simulations undertaken with the training data revealed that the constructed model was useable. The optimized neural network was used for optimization of formulation with desirable release characteristics and the results indicated that there was agreement between the predicted formulation and the manufactured formulation. This work illustrates the possible utility of artificial neural networks for the optimization of pharmaceutical formulations with desirable performance characteristics.
- Full Text:
- Date Issued: 2010
- Authors: Chaibva, Faith A , Burton, Michael , Walker, Roderick B
- Date: 2010
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Article
- Identifier: vital:6352 , http://hdl.handle.net/10962/d1006034
- Description: An artificial neural network was used to optimize the release of salbutamol sulfate from hydrophilic matrix formulations. Model formulations to be used for training, testing and validating the neural network were manufactured with the aid of a central composite design with varying the levels of Methocel® K100M, xanthan gum, Carbopol® 974P and Surelease® as the input factors. In vitro dissolution time profiles at six different sampling times were used as target data in training the neural network for formulation optimization. A multi layer perceptron with one hidden layer was constructed using Matlab®, and the number of nodes in the hidden layer was optimized by trial and error to develop a model with the best predictive ability. The results revealed that a neural network with nine nodes was optimal for developing and optimizing formulations. Simulations undertaken with the training data revealed that the constructed model was useable. The optimized neural network was used for optimization of formulation with desirable release characteristics and the results indicated that there was agreement between the predicted formulation and the manufactured formulation. This work illustrates the possible utility of artificial neural networks for the optimization of pharmaceutical formulations with desirable performance characteristics.
- Full Text:
- Date Issued: 2010
Physical and biological coupling in eddies in the lee of the South-West Indian Ridge
- Ansorge, Isabelle J, Pakhomov, E A, Kaehler, Sven, Lutjeharms, Johan R E, Durgadoo, J V
- Authors: Ansorge, Isabelle J , Pakhomov, E A , Kaehler, Sven , Lutjeharms, Johan R E , Durgadoo, J V
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6493 , http://hdl.handle.net/10962/d1004477
- Description: Eddies have some decisive functions in the dynamics of the Southern Ocean ecosystems. This is particularly true in the Indian sector of the Southern Ocean, where a region of unusually high-mesoscale variability has been observed in the vicinity of the South-West Indian Ridge. In April 2003, three eddies were studied: eddy A, a recently spawned anticyclone south of the Antarctic Polar Front (APF),; eddy B, an anticyclone north of lying between the Subantarctic Front and the APF; and eddy C, a cyclone north of the APF west of the ridge. Elevated concentrations of total Chl-a coincided with the edges of the cyclonic eddy, whereas both anticyclonic eddies A and B were characterised by low total Chl-a concentrations. Biologically, the two anticyclonic eddies A and B were distinctly different in their biogeographic origin. The zooplankton community in the larger anticyclonic eddy A was similar in composition to the Antarctic Polar Frontal Zone (APFZ) community with an addition of some Antarctic species suggesting an origin just north of the APF. In contrast, the species composition within the second anticyclonic eddy B appeared to be more typical of the transitional nature of the APFZ, comprising species of both subantarctic and subtropical origin and thus influenced by intrusions of water masses from both north and south of the Subantarctic Front. Back-tracking of these features shows that the biological composition clearly demarcates the hydrographic origin of these features.
- Full Text:
- Date Issued: 2010
- Authors: Ansorge, Isabelle J , Pakhomov, E A , Kaehler, Sven , Lutjeharms, Johan R E , Durgadoo, J V
- Date: 2010
- Language: English
- Type: Article
- Identifier: vital:6493 , http://hdl.handle.net/10962/d1004477
- Description: Eddies have some decisive functions in the dynamics of the Southern Ocean ecosystems. This is particularly true in the Indian sector of the Southern Ocean, where a region of unusually high-mesoscale variability has been observed in the vicinity of the South-West Indian Ridge. In April 2003, three eddies were studied: eddy A, a recently spawned anticyclone south of the Antarctic Polar Front (APF),; eddy B, an anticyclone north of lying between the Subantarctic Front and the APF; and eddy C, a cyclone north of the APF west of the ridge. Elevated concentrations of total Chl-a coincided with the edges of the cyclonic eddy, whereas both anticyclonic eddies A and B were characterised by low total Chl-a concentrations. Biologically, the two anticyclonic eddies A and B were distinctly different in their biogeographic origin. The zooplankton community in the larger anticyclonic eddy A was similar in composition to the Antarctic Polar Frontal Zone (APFZ) community with an addition of some Antarctic species suggesting an origin just north of the APF. In contrast, the species composition within the second anticyclonic eddy B appeared to be more typical of the transitional nature of the APFZ, comprising species of both subantarctic and subtropical origin and thus influenced by intrusions of water masses from both north and south of the Subantarctic Front. Back-tracking of these features shows that the biological composition clearly demarcates the hydrographic origin of these features.
- Full Text:
- Date Issued: 2010
Politics, latent and overt, in Hill of Fools
- Authors: Wright, Laurence
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:7064 , http://hdl.handle.net/10962/d1007430
- Description: [From the text]: R. L. Peteni’s novel Hill of Fools (1976) is a work that benefits greatly when Collingwood’s maxim is observed. The author’s family history and the circumstances surrounding the book’s publication add a dimension of political and social meaning which its surface deliberately occludes. Perhaps more importantly, while the story can readily be enjoyed, the quality of sensibility behind the work is not readily accessed without understanding some of the socio-political background.
- Full Text:
- Date Issued: 2004
- Authors: Wright, Laurence
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:7064 , http://hdl.handle.net/10962/d1007430
- Description: [From the text]: R. L. Peteni’s novel Hill of Fools (1976) is a work that benefits greatly when Collingwood’s maxim is observed. The author’s family history and the circumstances surrounding the book’s publication add a dimension of political and social meaning which its surface deliberately occludes. Perhaps more importantly, while the story can readily be enjoyed, the quality of sensibility behind the work is not readily accessed without understanding some of the socio-political background.
- Full Text:
- Date Issued: 2004
Presidential Address
- Date: 1962-04
- 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/10948/33978 , vital:33171 , Bulk File 7
- Description: This is a Presidential Address given by the notable IB Tabata at APDUSA's first National Conference.
- Full Text: false
- Date Issued: 1962-04
- Date: 1962-04
- 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/10948/33978 , vital:33171 , Bulk File 7
- Description: This is a Presidential Address given by the notable IB Tabata at APDUSA's first National Conference.
- Full Text: false
- Date Issued: 1962-04
Pretopological and topological lattice-valued convergence spaces
- Authors: Jäger, Gunter
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6827 , http://hdl.handle.net/10962/d1012337
- Description: We show that the classical axiom which characterizes pretopological convergence spaces splits into two axioms in the general Heyting algebra-valued case. Furthermore we present a generalization of Kowalski’s diagonal condition to the lattice-valued case.
- Full Text:
- Date Issued: 2007
- Authors: Jäger, Gunter
- Date: 2007
- Language: English
- Type: text , Article
- Identifier: vital:6827 , http://hdl.handle.net/10962/d1012337
- Description: We show that the classical axiom which characterizes pretopological convergence spaces splits into two axioms in the general Heyting algebra-valued case. Furthermore we present a generalization of Kowalski’s diagonal condition to the lattice-valued case.
- Full Text:
- Date Issued: 2007
Radiocarbon dates and the Late Quaternary palaeogeography of the Province of the Eastern Cape, South Africa
- Authors: Lewis, Colin A
- Date: 2002
- Language: English
- Type: Article
- Identifier: vital:6693 , http://hdl.handle.net/10962/d1006728
- Description: A total of 193 dates are listed from the Eastern Cape. Middle Stone Age hunter-gatherers existed in the Drakensberg prior to the rigours of cold climatic conditions after ca. 22,000 BP. These uplands were reoccupied under more favourable climatic conditions after ca. 12,600 BP but were apparently abandoned between ca. 6000 BP and 3000 BP. Hunter-gatherer occupation throughout the Holocene is indicated at lower altitudes, with in-migration of pastoralists ca. 1800 BP in the Fish River area, and with Iron Age farmers entering coastal districts and adjacent river valleys from ca. 1400 BP. Sand dunes accumulated in the Holocene adjacent to the Indian Ocean. Flood plain development in the early Holocene was succeeded by incision of rivers in the later Holocene. Flood plain deposition began again in the Southern Drakensberg ca. 1000 BP. Palynological studies evidence marked climatic oscillations around the Late Glacial/Holocene boundary, with apparent stability at high altitude subsequent to 2700 BP.
- Full Text:
- Date Issued: 2002
- Authors: Lewis, Colin A
- Date: 2002
- Language: English
- Type: Article
- Identifier: vital:6693 , http://hdl.handle.net/10962/d1006728
- Description: A total of 193 dates are listed from the Eastern Cape. Middle Stone Age hunter-gatherers existed in the Drakensberg prior to the rigours of cold climatic conditions after ca. 22,000 BP. These uplands were reoccupied under more favourable climatic conditions after ca. 12,600 BP but were apparently abandoned between ca. 6000 BP and 3000 BP. Hunter-gatherer occupation throughout the Holocene is indicated at lower altitudes, with in-migration of pastoralists ca. 1800 BP in the Fish River area, and with Iron Age farmers entering coastal districts and adjacent river valleys from ca. 1400 BP. Sand dunes accumulated in the Holocene adjacent to the Indian Ocean. Flood plain development in the early Holocene was succeeded by incision of rivers in the later Holocene. Flood plain deposition began again in the Southern Drakensberg ca. 1000 BP. Palynological studies evidence marked climatic oscillations around the Late Glacial/Holocene boundary, with apparent stability at high altitude subsequent to 2700 BP.
- Full Text:
- Date Issued: 2002
Recent progress in electrochemical oxidation of saccharides at gold and copper electrodes in alkaline solutions
- Torto, N
- Authors: Torto, N
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6599 , http://hdl.handle.net/10962/d1004348
- Description: This article reviews the progress made in the past 10 years, on electrochemical oxidation of saccharides in alkaline media for gold and copper electrodes. The mechanism and processes associated with the electrochemical oxidation of saccharides at native and surface coated electrodes continues to be of great interest. Despite the effort and various mechanisms proposed, still the need for an electrochemically active material that understands the complexity associated with saccharides continues to increase as their detection poses a challenge for bioanalytical chemistry and liquid chromatography.
- Full Text:
- Date Issued: 2009
- Authors: Torto, N
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6599 , http://hdl.handle.net/10962/d1004348
- Description: This article reviews the progress made in the past 10 years, on electrochemical oxidation of saccharides in alkaline media for gold and copper electrodes. The mechanism and processes associated with the electrochemical oxidation of saccharides at native and surface coated electrodes continues to be of great interest. Despite the effort and various mechanisms proposed, still the need for an electrochemically active material that understands the complexity associated with saccharides continues to increase as their detection poses a challenge for bioanalytical chemistry and liquid chromatography.
- Full Text:
- Date Issued: 2009
Resistance or tolerance: an examination of aphid (Sitobion yakini) phloem feeding on Betta and Betta-Dn wheat (Triticum aestivum)
- De Wet, L R, Botha, Christiaan E J
- Authors: De Wet, L R , Botha, Christiaan E J
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6517 , http://hdl.handle.net/10962/d1005945
- Description: Engineering pest resistance into crops is important. However, the mechanisms of resistance are not clearly understood. In this study, we examined the effects of aphid feeding on Russian wheat aphid-resistant and -susceptible cultivars of wheat (Triticum aestivum L.); Betta-Dn and Betta, respectively, by the grass aphid, Sitobion yakini (Eastop). These cultivars were grown with or without aphid colonies. In each case, we examined the plants specifically for the formation of wound callose associated with the phloem, using aniline blue and fluorescence microscopy. We observed that aphid feeding stimulated the formation of wound callose in the susceptible cultivar, but that callose was comparatively reduced in the resistant cultivar of wheat. In a separate series of experiments, the xenobiotic, 5, 6-carboxyfluorescein diacetate was applied to attached sink leaves, distal to feeding aphids. When leaf segments were examined four hours after application, little evidence of phloem transport of the fluorescent cleavage product, 5, 6-carboxyfluorescein (5, 6-CF), was evident below known aphid-probed sieve tubes. Low levels or absence of 5, 6-CF indicates that either the aphids have successfully redirected sap to themselves, or that the phloem is no longer functional. In contrast, 5, 6-CF transport was evident below sites of aphid probing in Betta-Dn, suggesting that the phloem was still capable of long-distance transport. In addition, callose deposition was reduced in Betta-Dn leaf phloem and it is surmised that transport was not as affected by aphid feeding in the resistant cultivar. This indicates that the ‘resistant’ wheat cultivar may in fact be tolerant to aphid feeding by successfully overcoming the nutrient drain that feeding aphids imposed on the phloem transport system.
- Full Text:
- Date Issued: 2007
- Authors: De Wet, L R , Botha, Christiaan E J
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6517 , http://hdl.handle.net/10962/d1005945
- Description: Engineering pest resistance into crops is important. However, the mechanisms of resistance are not clearly understood. In this study, we examined the effects of aphid feeding on Russian wheat aphid-resistant and -susceptible cultivars of wheat (Triticum aestivum L.); Betta-Dn and Betta, respectively, by the grass aphid, Sitobion yakini (Eastop). These cultivars were grown with or without aphid colonies. In each case, we examined the plants specifically for the formation of wound callose associated with the phloem, using aniline blue and fluorescence microscopy. We observed that aphid feeding stimulated the formation of wound callose in the susceptible cultivar, but that callose was comparatively reduced in the resistant cultivar of wheat. In a separate series of experiments, the xenobiotic, 5, 6-carboxyfluorescein diacetate was applied to attached sink leaves, distal to feeding aphids. When leaf segments were examined four hours after application, little evidence of phloem transport of the fluorescent cleavage product, 5, 6-carboxyfluorescein (5, 6-CF), was evident below known aphid-probed sieve tubes. Low levels or absence of 5, 6-CF indicates that either the aphids have successfully redirected sap to themselves, or that the phloem is no longer functional. In contrast, 5, 6-CF transport was evident below sites of aphid probing in Betta-Dn, suggesting that the phloem was still capable of long-distance transport. In addition, callose deposition was reduced in Betta-Dn leaf phloem and it is surmised that transport was not as affected by aphid feeding in the resistant cultivar. This indicates that the ‘resistant’ wheat cultivar may in fact be tolerant to aphid feeding by successfully overcoming the nutrient drain that feeding aphids imposed on the phloem transport system.
- Full Text:
- Date Issued: 2007