Regulation within the supracellular highway - plasmodesma are the key
- Botha, Christiaan E J, Cross, Robin H M
- Authors: Botha, Christiaan E J , Cross, Robin H M
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6500 , http://hdl.handle.net/10962/d1005918
- Description: Plasmodesmal connections are unique, highly dynamic intercellular structures that are lined by the plasmamembrane. They are believed to be a vital intercellular communication channel between living cells, linking numbers of living cells into interconnected, highly specialised cellular domains, thus enabling the plant to act as an integrated organism. Their evolution in the higher plant was inevitable. It is accepted that cell heterogeneity rather than cell divergence pressurised developing plant systems along a route that led to the development of intercellular passages and connections. With time these connections have evolved to allow some degree of regulation and traffic control. This paper explores some of the structure/function relationships in plasmodesmata. Attention is focused on the potential role of the neck region of these remarkable structures and discusses models which may explain the processes involved in regulating the movement of substances from cell to cell.
- Full Text: false
- Date Issued: 2001
- Authors: Botha, Christiaan E J , Cross, Robin H M
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6500 , http://hdl.handle.net/10962/d1005918
- Description: Plasmodesmal connections are unique, highly dynamic intercellular structures that are lined by the plasmamembrane. They are believed to be a vital intercellular communication channel between living cells, linking numbers of living cells into interconnected, highly specialised cellular domains, thus enabling the plant to act as an integrated organism. Their evolution in the higher plant was inevitable. It is accepted that cell heterogeneity rather than cell divergence pressurised developing plant systems along a route that led to the development of intercellular passages and connections. With time these connections have evolved to allow some degree of regulation and traffic control. This paper explores some of the structure/function relationships in plasmodesmata. Attention is focused on the potential role of the neck region of these remarkable structures and discusses models which may explain the processes involved in regulating the movement of substances from cell to cell.
- Full Text: false
- Date Issued: 2001
The myth of authenticity : folktales and nationalism in the 'new South Africa'
- Authors: Naidu, Samantha
- Date: 2001
- Language: English
- Type: Article , text
- Identifier: vital:26378 , http://hdl.handle.net/10962/54047 , https://orcid.org/0000-0001-9456-8657
- Description: Folktales texts are published in glorious, polychromatic, innovative forms that promote the texts as both culturally educational and entertaining.
- Full Text: false
- Date Issued: 2001
- Authors: Naidu, Samantha
- Date: 2001
- Language: English
- Type: Article , text
- Identifier: vital:26378 , http://hdl.handle.net/10962/54047 , https://orcid.org/0000-0001-9456-8657
- Description: Folktales texts are published in glorious, polychromatic, innovative forms that promote the texts as both culturally educational and entertaining.
- Full Text: false
- Date Issued: 2001
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
A continuous process for the biological treatment of heavy metal contaminated acid mine water
- Van Hille, R P, Boshoff, G A, Rose, Peter D, Duncan, John R
- Authors: Van Hille, R P , Boshoff, G A , Rose, Peter D , Duncan, John R
- Date: 1999
- Language: English
- Type: Article
- Identifier: vital:6464 , http://hdl.handle.net/10962/d1005793 , dx.doi.org/10.1016/S0921-3449(99)00010-5
- Description: Alkaline precipitation of heavy metals from acidic water streams is a popular and long standing treatment process. While this process is efficient it requires the continuous addition of an alkaline material, such as lime. In the long term or when treating large volumes of effluent this process becomes expensive, with costs in the mining sector routinely exceeding millions of rands annually. The process described below utilises alkalinity generated by the alga Spirulina sp., in a continuous system to precipitate heavy metals. The design of the system separates the algal component from the metal containing stream to overcome metal toxicity. The primary treatment process consistently removed over 99% of the iron (98.9 mg/l) and between 80 and 95% of the zinc (7.16 mg/l) and lead (2.35 mg/l) over a 14-day period (20 l effluent treated). In addition the pH of the raw effluent was increased from 1.8 to over 7 in the post-treatment stream. Secondary treatment and polishing steps depend on the nature of the effluent treated. In the case of the high sulphate effluent the treated stream was passed into an anaerobic digester at a rate of 4 l/day. The combination of the primary and secondary treatments effected a removal of over 95% of all metals tested for as well as a 90% reduction in the sulphate load. The running cost of such a process would be low as the salinity and nutrient requirements for the algal culture could be provided by using tannery effluent or a combination of saline water and sewage. This would have the additional benefit of treating either a tannery or sewage effluent as part of an integrated process.
- Full Text:
- Date Issued: 1999
- Authors: Van Hille, R P , Boshoff, G A , Rose, Peter D , Duncan, John R
- Date: 1999
- Language: English
- Type: Article
- Identifier: vital:6464 , http://hdl.handle.net/10962/d1005793 , dx.doi.org/10.1016/S0921-3449(99)00010-5
- Description: Alkaline precipitation of heavy metals from acidic water streams is a popular and long standing treatment process. While this process is efficient it requires the continuous addition of an alkaline material, such as lime. In the long term or when treating large volumes of effluent this process becomes expensive, with costs in the mining sector routinely exceeding millions of rands annually. The process described below utilises alkalinity generated by the alga Spirulina sp., in a continuous system to precipitate heavy metals. The design of the system separates the algal component from the metal containing stream to overcome metal toxicity. The primary treatment process consistently removed over 99% of the iron (98.9 mg/l) and between 80 and 95% of the zinc (7.16 mg/l) and lead (2.35 mg/l) over a 14-day period (20 l effluent treated). In addition the pH of the raw effluent was increased from 1.8 to over 7 in the post-treatment stream. Secondary treatment and polishing steps depend on the nature of the effluent treated. In the case of the high sulphate effluent the treated stream was passed into an anaerobic digester at a rate of 4 l/day. The combination of the primary and secondary treatments effected a removal of over 95% of all metals tested for as well as a 90% reduction in the sulphate load. The running cost of such a process would be low as the salinity and nutrient requirements for the algal culture could be provided by using tannery effluent or a combination of saline water and sewage. This would have the additional benefit of treating either a tannery or sewage effluent as part of an integrated process.
- Full Text:
- Date Issued: 1999
The honeybees, Apis mellifera Linnaeus (Hymenoptera: Apidae) of woodland savanna of southeastern Africa
- Radloff, Sarah E, Hepburn, H Randall, Villet, Martin H
- Authors: Radloff, Sarah E , Hepburn, H Randall , Villet, Martin H
- Date: 1997
- Language: English
- Type: Article
- Identifier: vital:6829 , http://hdl.handle.net/10962/d1012341
- Description: The morphometric characters and sting pheromones of worker honeybees, Apis mellifera Linnaeus, were analysed by multivariate methods to identify discrete populations in the southeastern woodland savanna of Africa. A discrete population in Mozambique is classified as A. m. litorea Smith, a second in Zimbabwe as A. m. scutellata Lepeletier and a third group in southwestern Zambia as A.m. adansonii Latreille. A zone of introgression between the last two subspecies occurs in south-central Zambia and in the Zambezi Valley.
- Full Text:
- Date Issued: 1997
- Authors: Radloff, Sarah E , Hepburn, H Randall , Villet, Martin H
- Date: 1997
- Language: English
- Type: Article
- Identifier: vital:6829 , http://hdl.handle.net/10962/d1012341
- Description: The morphometric characters and sting pheromones of worker honeybees, Apis mellifera Linnaeus, were analysed by multivariate methods to identify discrete populations in the southeastern woodland savanna of Africa. A discrete population in Mozambique is classified as A. m. litorea Smith, a second in Zimbabwe as A. m. scutellata Lepeletier and a third group in southwestern Zambia as A.m. adansonii Latreille. A zone of introgression between the last two subspecies occurs in south-central Zambia and in the Zambezi Valley.
- Full Text:
- Date Issued: 1997
Racial segregation in East London, 1836-1948
- Authors: Nel, Etienne L
- Date: 1991
- Language: English
- Type: Article
- Identifier: vital:6717 , http://hdl.handle.net/10962/d1006790
- Description: Urban racial segregation in East London has a distinctive heritage, making the city one of South Africa's most segregated in the pre-Union era. Segregation was initiated by the British military in the then colony of British Kaffraria, and was later enhanced by successive municipal councils. Municipal ordinances ensured exceptionally high levels of segregation in the city during the 19th century. The enforcement of Asian segregation in this era is noteworthy. Urban planning in the 20th century resulted as much from local as national considerations and legislation. Segregation was a reality in East London prior to the passage of the Group Areas Act. The deteriorating social circumstances in the long-segregated African areas in particular receive special mention, as do government attempts to rectify the situation through the institution of state commissions.
- Full Text: false
- Date Issued: 1991
- Authors: Nel, Etienne L
- Date: 1991
- Language: English
- Type: Article
- Identifier: vital:6717 , http://hdl.handle.net/10962/d1006790
- Description: Urban racial segregation in East London has a distinctive heritage, making the city one of South Africa's most segregated in the pre-Union era. Segregation was initiated by the British military in the then colony of British Kaffraria, and was later enhanced by successive municipal councils. Municipal ordinances ensured exceptionally high levels of segregation in the city during the 19th century. The enforcement of Asian segregation in this era is noteworthy. Urban planning in the 20th century resulted as much from local as national considerations and legislation. Segregation was a reality in East London prior to the passage of the Group Areas Act. The deteriorating social circumstances in the long-segregated African areas in particular receive special mention, as do government attempts to rectify the situation through the institution of state commissions.
- Full Text: false
- Date Issued: 1991
The South African sugar industry
- Authors: Lewis, Colin A
- Date: 1990
- Language: English
- Type: Article
- Identifier: vital:6695 , http://hdl.handle.net/10962/d1006730
- Description: The sugar industry was established in Natal in the mid-nineteenth century. By the 1980s, South Africa produced c. 2 million metric tons of sugar per annum and, directly or indirectly, the industry supported almost one million people. Exports, which amounted for almost half the sugar produced in the 1970s, declined during the 1980s and low prices together with American and Canadian sanctions have forced the industry to consider alternative uses for sugar cane.
- Full Text: false
- Date Issued: 1990
- Authors: Lewis, Colin A
- Date: 1990
- Language: English
- Type: Article
- Identifier: vital:6695 , http://hdl.handle.net/10962/d1006730
- Description: The sugar industry was established in Natal in the mid-nineteenth century. By the 1980s, South Africa produced c. 2 million metric tons of sugar per annum and, directly or indirectly, the industry supported almost one million people. Exports, which amounted for almost half the sugar produced in the 1970s, declined during the 1980s and low prices together with American and Canadian sanctions have forced the industry to consider alternative uses for sugar cane.
- Full Text: false
- Date Issued: 1990
The Educational Journal
- Date: 1964-09
- Subjects: Education –- South Africa , South Africa -- Politics and government , Government, Resistance to -- South Africa
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/34702 , vital:33421 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa.
- Full Text: false
- Date Issued: 1964-09
- Date: 1964-09
- Subjects: Education –- South Africa , South Africa -- Politics and government , Government, Resistance to -- South Africa
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/34702 , vital:33421 , Bulk File 7
- Description: The Educational Journal was the official organ of the Teachers' League of South Africa and focussed on education within the context of a racialized South Africa.
- Full Text: false
- Date Issued: 1964-09