An interdisciplinary cruise dedicated to understanding ocean eddies upstream of the Prince Edward Islands
- Ansorge, Isabelle J, Froneman, P William, Lutjeharms, Johan R E, Bernard, Kim S, Lange, Louise, Lukáč, D, Backburg, B, Blake, Justin, Bland, S, Burls, N, Davies-Coleman, Michael T, Gerber, R, Gildenhuys, S, Hayes-Foley, P, Ludford, A, Manzoni, T, Robertson, E, Southey, D, Swart, S, Van Rensburg, D, Wynne, S
- Authors: Ansorge, Isabelle J , Froneman, P William , Lutjeharms, Johan R E , Bernard, Kim S , Lange, Louise , Lukáč, D , Backburg, B , Blake, Justin , Bland, S , Burls, N , Davies-Coleman, Michael T , Gerber, R , Gildenhuys, S , Hayes-Foley, P , Ludford, A , Manzoni, T , Robertson, E , Southey, D , Swart, S , Van Rensburg, D , Wynne, S
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6830 , http://hdl.handle.net/10962/d1007566
- Description: A detailed hydrographic and biological survey was carried out in the region of the South-West Indian Ridge during April 2004. Altimetry and hydrographic data have identified this region as an area of high flow variability. Hydrographic data revealed that here the Subantarctic Polar Front (SAF) and Antarctic Polar Front (APF) converge to form a highly intense frontal system. Water masses identified during the survey showed a distinct separation in properties between the northwestern and southeastern corners. In the north-west, water masses were distinctly Subantarctic (>8.5°C, salinity >34.2), suggesting that the SAF lay extremely far to the south. In the southeast corner water masses were typical of the Antarctic zone, showing a distinct subsurface temperature minimum of <2.5°C. Total integrated chl-a concentration during the survey ranged from 4.15 to 22.81 mg chl-a m[superscript (-2)], with the highest concentrations recorded at stations occupied in the frontal region. These data suggest that the region of the South-West Indian Ridge represents not only an area of elevated biological activity but also acts as a strong biogeographic barrier to the spatial distribution of zooplankton.
- Full Text:
- Date Issued: 2004
- Authors: Ansorge, Isabelle J , Froneman, P William , Lutjeharms, Johan R E , Bernard, Kim S , Lange, Louise , Lukáč, D , Backburg, B , Blake, Justin , Bland, S , Burls, N , Davies-Coleman, Michael T , Gerber, R , Gildenhuys, S , Hayes-Foley, P , Ludford, A , Manzoni, T , Robertson, E , Southey, D , Swart, S , Van Rensburg, D , Wynne, S
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6830 , http://hdl.handle.net/10962/d1007566
- Description: A detailed hydrographic and biological survey was carried out in the region of the South-West Indian Ridge during April 2004. Altimetry and hydrographic data have identified this region as an area of high flow variability. Hydrographic data revealed that here the Subantarctic Polar Front (SAF) and Antarctic Polar Front (APF) converge to form a highly intense frontal system. Water masses identified during the survey showed a distinct separation in properties between the northwestern and southeastern corners. In the north-west, water masses were distinctly Subantarctic (>8.5°C, salinity >34.2), suggesting that the SAF lay extremely far to the south. In the southeast corner water masses were typical of the Antarctic zone, showing a distinct subsurface temperature minimum of <2.5°C. Total integrated chl-a concentration during the survey ranged from 4.15 to 22.81 mg chl-a m[superscript (-2)], with the highest concentrations recorded at stations occupied in the frontal region. These data suggest that the region of the South-West Indian Ridge represents not only an area of elevated biological activity but also acts as a strong biogeographic barrier to the spatial distribution of zooplankton.
- Full Text:
- Date Issued: 2004
Phylogeny, biogeography, and the evolution of life-history traits in Leucadendron (Proteaceae)
- Barker, Nigel P, Vanderpoorten, Alain, Morton, Cynthia M, Rourke, John P
- Authors: Barker, Nigel P , Vanderpoorten, Alain , Morton, Cynthia M , Rourke, John P
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6496 , http://hdl.handle.net/10962/d1004491
- Description: Leucadendron is a moderately large genus of Proteaceae almost entirely restricted to the Cape Floristic Region of southern Africa. The genus is unusual in being dioecious and sexually dimorphic. ITS sequence data were obtained from 62 of the 96 currently recognized taxa (85 species and 11 subspecies). Phylogenetic analyses were conducted under Maximum Likelihood and parsimony and resolved nine groups of species with varying degrees of bootstrap support, but relationships between these groups are largely unsupported. The phylogeny conflicts with the current taxonomic arrangement, which is based mainly on fruit morphology. The two sections of the genus, Alatosperma and Leucadendron, and several subsections within these sections, are resolved as non-monophyletic. This means that taxonomically important characters (such as fruit shape) have evolved multiple times, as the species with nutlike fruit (resolved into two of the nine groups) appear to have evolved independently from ancestors with winged fruit. Based on the topology obtained, the life history traits of anemophily, myrmechochory, and re-sprouting have also originated multiple times. Dispersal–Vicariance (DIVA) analysis suggests that the genus had an ancestral area in the Karoo Mountain and Southeastern phytogeographic centres of endemism in the southwestern Cape. , Elsevier
- Full Text:
- Date Issued: 2004
- Authors: Barker, Nigel P , Vanderpoorten, Alain , Morton, Cynthia M , Rourke, John P
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6496 , http://hdl.handle.net/10962/d1004491
- Description: Leucadendron is a moderately large genus of Proteaceae almost entirely restricted to the Cape Floristic Region of southern Africa. The genus is unusual in being dioecious and sexually dimorphic. ITS sequence data were obtained from 62 of the 96 currently recognized taxa (85 species and 11 subspecies). Phylogenetic analyses were conducted under Maximum Likelihood and parsimony and resolved nine groups of species with varying degrees of bootstrap support, but relationships between these groups are largely unsupported. The phylogeny conflicts with the current taxonomic arrangement, which is based mainly on fruit morphology. The two sections of the genus, Alatosperma and Leucadendron, and several subsections within these sections, are resolved as non-monophyletic. This means that taxonomically important characters (such as fruit shape) have evolved multiple times, as the species with nutlike fruit (resolved into two of the nine groups) appear to have evolved independently from ancestors with winged fruit. Based on the topology obtained, the life history traits of anemophily, myrmechochory, and re-sprouting have also originated multiple times. Dispersal–Vicariance (DIVA) analysis suggests that the genus had an ancestral area in the Karoo Mountain and Southeastern phytogeographic centres of endemism in the southwestern Cape. , Elsevier
- Full Text:
- Date Issued: 2004
A yellowwood by any other name: molecular systematics and the taxonomy of Podocarpus and the Podocarpaceae in southern Africa
- Barker, Nigel P, Muller, E M, Mill, R R
- Authors: Barker, Nigel P , Muller, E M , Mill, R R
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6495 , http://hdl.handle.net/10962/d1004488
- Description: We briefly review the taxonomic history of the Podocarpaceae, with an emphasis on the recognition of numerous segregate genera out of Podocarpus sensu lato. Despite some controversy over the recognition of these genera, molecular data (DNA sequences) provide evidence that supports this taxonomy. The implications for African Podocarpaceae are discussed. In particular, molecular data support the recognition of Afrocarpus as distinct from Podocarpus. Additional taxonomic problems concerning the possible segregation of Podocarpus milanjianus from P. latifolius are addressed using DNA sequence data from the nuclear internal transcribed spacer 2 (ITS2) region. Results of this are inconclusive, and suggest that alternative DNA-based evidence, such as from AFLPs or microsatellites, may be more informative in resolving such species complexes in African Podocarpus.
- Full Text:
- Date Issued: 2004
- Authors: Barker, Nigel P , Muller, E M , Mill, R R
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6495 , http://hdl.handle.net/10962/d1004488
- Description: We briefly review the taxonomic history of the Podocarpaceae, with an emphasis on the recognition of numerous segregate genera out of Podocarpus sensu lato. Despite some controversy over the recognition of these genera, molecular data (DNA sequences) provide evidence that supports this taxonomy. The implications for African Podocarpaceae are discussed. In particular, molecular data support the recognition of Afrocarpus as distinct from Podocarpus. Additional taxonomic problems concerning the possible segregation of Podocarpus milanjianus from P. latifolius are addressed using DNA sequence data from the nuclear internal transcribed spacer 2 (ITS2) region. Results of this are inconclusive, and suggest that alternative DNA-based evidence, such as from AFLPs or microsatellites, may be more informative in resolving such species complexes in African Podocarpus.
- Full Text:
- Date Issued: 2004
Molecular chaperones in biology, medicine and protein biotechnology
- Boshoff, Aileen, Nicoll, William S, Hennessy, Fritha, Ludewig, M H, Daniel, Sheril, Modisakeng, Keoagile W, Shonhai, Addmore, McNamara, Caryn, Bradley, Graeme, Blatch, Gregory L
- Authors: Boshoff, Aileen , Nicoll, William S , Hennessy, Fritha , Ludewig, M H , Daniel, Sheril , Modisakeng, Keoagile W , Shonhai, Addmore , McNamara, Caryn , Bradley, Graeme , Blatch, Gregory L
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6457 , http://hdl.handle.net/10962/d1004479
- Description: Molecular chaperones consist of several highly conserved families of proteins, many of which consist of heat shock proteins. The primary function of molecular chaperones is to facilitate the folding or refolding of proteins, and therefore they play an important role in diverse cellular processes including protein synthesis, protein translocation, and the refolding or degradation of proteins after cell stress. Cells are often exposed to different stressors, resulting in protein misfolding and aggregation. It is now well established that the levels of certain molecular chaperones are elevated during stress to provide protection to the cell. The focus of this review is on the impact of molecular chaperones in biology, medicine and protein biotechnology, and thus covers both fundamental and applied aspects of chaperone biology. Attention is paid to the functions and applications of molecular chaperones from bacterial and eukaryotic cells, focusing on the heat shock proteins 90 (Hsp90), 70 (Hsp70) and 40 (Hsp40) classes of chaperones, respectively. The role of these classes of chaperones in human diseases is discussed, as well as the parts played by chaperones produced by the causative agents of malaria and trypanosomiasis. Recent advances have seen the application of chaperones in improving the yields of a particular target protein in recombinant protein production. The prospects for the targeted use of molecular chaperones for the over-production of recombinant proteins is critically reviewed, and current research on these chaperones at Rhodes University is also discussed.
- Full Text:
- Date Issued: 2004
- Authors: Boshoff, Aileen , Nicoll, William S , Hennessy, Fritha , Ludewig, M H , Daniel, Sheril , Modisakeng, Keoagile W , Shonhai, Addmore , McNamara, Caryn , Bradley, Graeme , Blatch, Gregory L
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6457 , http://hdl.handle.net/10962/d1004479
- Description: Molecular chaperones consist of several highly conserved families of proteins, many of which consist of heat shock proteins. The primary function of molecular chaperones is to facilitate the folding or refolding of proteins, and therefore they play an important role in diverse cellular processes including protein synthesis, protein translocation, and the refolding or degradation of proteins after cell stress. Cells are often exposed to different stressors, resulting in protein misfolding and aggregation. It is now well established that the levels of certain molecular chaperones are elevated during stress to provide protection to the cell. The focus of this review is on the impact of molecular chaperones in biology, medicine and protein biotechnology, and thus covers both fundamental and applied aspects of chaperone biology. Attention is paid to the functions and applications of molecular chaperones from bacterial and eukaryotic cells, focusing on the heat shock proteins 90 (Hsp90), 70 (Hsp70) and 40 (Hsp40) classes of chaperones, respectively. The role of these classes of chaperones in human diseases is discussed, as well as the parts played by chaperones produced by the causative agents of malaria and trypanosomiasis. Recent advances have seen the application of chaperones in improving the yields of a particular target protein in recombinant protein production. The prospects for the targeted use of molecular chaperones for the over-production of recombinant proteins is critically reviewed, and current research on these chaperones at Rhodes University is also discussed.
- Full Text:
- Date Issued: 2004
Reduction in transport in wheat (Triticum aestivum) is caused by sustained phloem feeding by the Russian wheat aphid (Diuraphis noxia)
- Botha, Christiaan E J, Matsiliza, Babalwa
- Authors: Botha, Christiaan E J , Matsiliza, Babalwa
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6498 , http://hdl.handle.net/10962/d1004498
- Description: The Russian wheat aphid (Diuraphis noxia) feeds preferentially from the phloem of longitudinal veins of nonresistant wheat leaves. The xenobiotic, 5,6-CFDA was applied to exposed leaf blade mesophyll cells in control and aphid-infested plants. In control plants, the fluorophore moved approximately 5–6cm from the point of application of 5,6-CFDA within 3h of application. The fluorochrome was transported in the sieve tube companion cell complex, including those in the numerous interconnecting transverse veins. Leaf blades on which the Russian wheat aphid had been feeding demonstrated a marked decrease in 5,6-CF transport. Aphids feeding on the leaves formed local sinks and redirected the fluorophore (and presumably associated assimilate) to the aphids’ gut, with little longitudinal translocation of 5,6-CF below inserted stylets or aphid feeding areas. Aniline blue staining revealed massive deposits of wound and reaction callose caused by the aphids, with callose associated with the sieve plates, pore-plasmodesma between the companion cells and their associated sieve tubes, as well as with plasmodesmal aggregates in parenchymatous elements within the vascular bundles. Leaves that had been colonised by aphids but from which the aphids were removed, showed extensive wound callose deposits, which persisted for up to 48h after removal of aphid colonies, suggesting that the damage caused by aphid feeding is a long-term, non-transient event in non-resistant plants.
- Full Text:
- Date Issued: 2004
- Authors: Botha, Christiaan E J , Matsiliza, Babalwa
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6498 , http://hdl.handle.net/10962/d1004498
- Description: The Russian wheat aphid (Diuraphis noxia) feeds preferentially from the phloem of longitudinal veins of nonresistant wheat leaves. The xenobiotic, 5,6-CFDA was applied to exposed leaf blade mesophyll cells in control and aphid-infested plants. In control plants, the fluorophore moved approximately 5–6cm from the point of application of 5,6-CFDA within 3h of application. The fluorochrome was transported in the sieve tube companion cell complex, including those in the numerous interconnecting transverse veins. Leaf blades on which the Russian wheat aphid had been feeding demonstrated a marked decrease in 5,6-CF transport. Aphids feeding on the leaves formed local sinks and redirected the fluorophore (and presumably associated assimilate) to the aphids’ gut, with little longitudinal translocation of 5,6-CF below inserted stylets or aphid feeding areas. Aniline blue staining revealed massive deposits of wound and reaction callose caused by the aphids, with callose associated with the sieve plates, pore-plasmodesma between the companion cells and their associated sieve tubes, as well as with plasmodesmal aggregates in parenchymatous elements within the vascular bundles. Leaves that had been colonised by aphids but from which the aphids were removed, showed extensive wound callose deposits, which persisted for up to 48h after removal of aphid colonies, suggesting that the damage caused by aphid feeding is a long-term, non-transient event in non-resistant plants.
- Full Text:
- Date Issued: 2004
The microstructure of plasmodesmata in internodal stem tissue of the Saccharum hybrid var. NCo376 : evidence for an apoplasmic loading pathway
- Botha, Christiaan E J, Cross, Robin H M, Gerber, Jacques
- Authors: Botha, Christiaan E J , Cross, Robin H M , Gerber, Jacques
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6494 , http://hdl.handle.net/10962/d1004487
- Description: The distribution, structure and functional state of plasmodesmata were investigated to gain a clearer understanding of the sucrose transport pathway to the storage parenchyma cells in stem tissue in Saccharum officinarum var. NCo376. Evidence from structural studies on sugarcane stems by electron microscopy indicated that there are numerous plasmodesmata from the vascular bundles through to the storage parenchyma cells in mature stem tissue. Our studies, supported by fluorescence microscopy and iontophoresis, indicate that there are functional plasmodesmata in the phloemunloading pathway from transport phloem tissue to the bundle sheath in Saccharum, which could support symplasmic transport; plasmodesmata outside of the sheath cells in the storage parenchyma appear to be constricted by sphincter-like structures within their neck regions. Staining with Aniline Blue revealed evidence of large callose deposits, which co-localized with plasmodesmatal aggregates in the walls of the storage parenchyma cells. This suggests that the sucrose transport into, and accumulation by, storage parenchyma of mature stem tissue is under apoplasmic control.
- Full Text:
- Date Issued: 2004
- Authors: Botha, Christiaan E J , Cross, Robin H M , Gerber, Jacques
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6494 , http://hdl.handle.net/10962/d1004487
- Description: The distribution, structure and functional state of plasmodesmata were investigated to gain a clearer understanding of the sucrose transport pathway to the storage parenchyma cells in stem tissue in Saccharum officinarum var. NCo376. Evidence from structural studies on sugarcane stems by electron microscopy indicated that there are numerous plasmodesmata from the vascular bundles through to the storage parenchyma cells in mature stem tissue. Our studies, supported by fluorescence microscopy and iontophoresis, indicate that there are functional plasmodesmata in the phloemunloading pathway from transport phloem tissue to the bundle sheath in Saccharum, which could support symplasmic transport; plasmodesmata outside of the sheath cells in the storage parenchyma appear to be constricted by sphincter-like structures within their neck regions. Staining with Aniline Blue revealed evidence of large callose deposits, which co-localized with plasmodesmatal aggregates in the walls of the storage parenchyma cells. This suggests that the sucrose transport into, and accumulation by, storage parenchyma of mature stem tissue is under apoplasmic control.
- Full Text:
- Date Issued: 2004
Market profiles and trade in medicinal plants in the Lowveld, South Africa
- Botha, Jenny, Witkowski, Ed T F, Shackleton, Charlie M
- Authors: Botha, Jenny , Witkowski, Ed T F , Shackleton, Charlie M
- Date: 2004
- Subjects: Kruger National Park
- Language: English
- Type: Article
- Identifier: vital:6625 , http://hdl.handle.net/10962/d1006817
- Description: Rising demand for medicinal plants has led to increased pressure on wild plant populations. This, combined with shrinking habitats, means that many species in South Africa are now facing local extinction. In 1997, a study was initiated to determine the extent of trade in medicinal plants in the South African Lowveld (the low lying plains to the east of the Drakensberg escarpment), and to investigate socio-economic factors influencing trade and resource management. Trade was not as extensive in the Lowveld as in major urban markets such as Durban or the Witwatersrand (Johannesburg and surrounding towns), either in terms of the quantity, number or range of species sold, or the numbers of people relying on the trade for an income. In markets assessed in Mpumalanga Province, 176 species were identified (71% of the vernacular names encountered in the market place), representing 69 plant families. In Limpopo, 70 different species were identified (84% of the vernacular names encountered in the market place), representing 40 families. Imports were significant in Mpumalanga (33% of the plants on offer), mainly from Mozambique. A detrended correspondence analysis showed substantial differences between species traded in Mpumalanga and those sold in Limpopo. There was little variation in the species stocked by vendors in Mpumalanga, regardless of the season, the attributes of the seller, or whether business was carried out in urban or rural areas. In contrast, there was considerable variation in the stock inventories of the Limpopo traders. Despite the lower levels of local trade, increased harvesting pressure is being experienced regionally, to meet demand in metropolitan centres such as the Witwatersrand. This study showed considerable local variation and complexities in the harvesting and marketing of medicinal plants, with both a national and an international dimension. This dual spatial scale presents both opportunities and challenges in the management of these plants, which need to be addressed simultaneously, particularly with respect to research requirements and development of predictive models and capacity. Cooperation in conservation strategies and policies is required at regional, national and international levels, while ensuring that management initiatives take into account local market conditions and the socio-economic realities facing both consumers and those who depend on the trade for their livelihoods.
- Full Text:
- Date Issued: 2004
- Authors: Botha, Jenny , Witkowski, Ed T F , Shackleton, Charlie M
- Date: 2004
- Subjects: Kruger National Park
- Language: English
- Type: Article
- Identifier: vital:6625 , http://hdl.handle.net/10962/d1006817
- Description: Rising demand for medicinal plants has led to increased pressure on wild plant populations. This, combined with shrinking habitats, means that many species in South Africa are now facing local extinction. In 1997, a study was initiated to determine the extent of trade in medicinal plants in the South African Lowveld (the low lying plains to the east of the Drakensberg escarpment), and to investigate socio-economic factors influencing trade and resource management. Trade was not as extensive in the Lowveld as in major urban markets such as Durban or the Witwatersrand (Johannesburg and surrounding towns), either in terms of the quantity, number or range of species sold, or the numbers of people relying on the trade for an income. In markets assessed in Mpumalanga Province, 176 species were identified (71% of the vernacular names encountered in the market place), representing 69 plant families. In Limpopo, 70 different species were identified (84% of the vernacular names encountered in the market place), representing 40 families. Imports were significant in Mpumalanga (33% of the plants on offer), mainly from Mozambique. A detrended correspondence analysis showed substantial differences between species traded in Mpumalanga and those sold in Limpopo. There was little variation in the species stocked by vendors in Mpumalanga, regardless of the season, the attributes of the seller, or whether business was carried out in urban or rural areas. In contrast, there was considerable variation in the stock inventories of the Limpopo traders. Despite the lower levels of local trade, increased harvesting pressure is being experienced regionally, to meet demand in metropolitan centres such as the Witwatersrand. This study showed considerable local variation and complexities in the harvesting and marketing of medicinal plants, with both a national and an international dimension. This dual spatial scale presents both opportunities and challenges in the management of these plants, which need to be addressed simultaneously, particularly with respect to research requirements and development of predictive models and capacity. Cooperation in conservation strategies and policies is required at regional, national and international levels, while ensuring that management initiatives take into account local market conditions and the socio-economic realities facing both consumers and those who depend on the trade for their livelihoods.
- Full Text:
- Date Issued: 2004
100 years of chemistry at Rhodes University
- Brown, Michael E, Eve, Desmond John, Kaye, Perry T, Rivett, Douglas E A, Watkins, Gareth M
- Authors: Brown, Michael E , Eve, Desmond John , Kaye, Perry T , Rivett, Douglas E A , Watkins, Gareth M
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6564 , http://hdl.handle.net/10962/d1004123
- Description: The history of Grahamstown is well documented and two books deal with the history of Rhodes University.1,2 Although the Chemistry Department was one of the founding departments, coverage in the official histories is minimal and sometimes inaccurate or misleading. The Rhodes University Centenary is an appropriate time to look back on some of the achievements of the department and some of its graduates over the past 100 years.
- Full Text:
- Date Issued: 2004
- Authors: Brown, Michael E , Eve, Desmond John , Kaye, Perry T , Rivett, Douglas E A , Watkins, Gareth M
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6564 , http://hdl.handle.net/10962/d1004123
- Description: The history of Grahamstown is well documented and two books deal with the history of Rhodes University.1,2 Although the Chemistry Department was one of the founding departments, coverage in the official histories is minimal and sometimes inaccurate or misleading. The Rhodes University Centenary is an appropriate time to look back on some of the achievements of the department and some of its graduates over the past 100 years.
- Full Text:
- Date Issued: 2004
Variability in pH, fCO2, oxygen and flux of CO2 in the surface water along a transect in the Atlantic sector of the Southern Ocean
- Chierici, M, Fransson, A, Turner, D R, Pakhomov, E A, Froneman, Pierre William
- Authors: Chierici, M , Fransson, A , Turner, D R , Pakhomov, E A , Froneman, Pierre William
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6847 , http://hdl.handle.net/10962/d1011105
- Description: Underway sampling and measurements of pH, fCO2, oxygen and Chlorophyll a (Chl a) were performed in the surface waters from Cape Town (South Africa) to Queen Maud Land (Antarctica) in the Atlantic sector of the Southern Ocean during the austral summer 1997/1998. From direct measurements of these parameters and from calculated fCO2 the oceanic carbon dioxide system was studied and related to hydrological and biological parameters. fCO2 was in general undersaturated relative to the atmosphere and showed a large variability with values ranging from 313 to 377 μatm with a mean value of 346±13 μatm. The undersaturation was more pronounced in areas associated with fronts where high Chl a and high pH in situ values were observed. Using shipboard wind speed data, estimates of the CO2 flux were made along the transect and during three mesoscale surveys on the northward return transect in the area of the Spring Ice Edge (SIE), the Winter Ice Edge (WIE) and in the Antarctic Polar Front (APF). The undersaturation observed during the transect caused the ocean to act as a sink for CO2 with a mean sea–air flux for the entire transect of −3±5 mmol m−2 d−1 with a large variability between −20 mmol m−2 d−1 (oceanic uptake) to 1.3 mmol m−2 d−1 (oceanic source). The lowest fCO2 values (largest oceanic uptake of CO2) were found at the southern boundary of the APF at 53°S, which coincided with a supersaturation in oxygen and high pH values. Oxygen concentrations were measured from 50°S to 63°S and varied between 324 and 359 μmol kg−1 with a mean value of 347±9 μmol kg−1. In general only small deviations from equilibrium oxygen saturation were observed (mean value=99±2%). However, in the SIE oxygen was clearly undersaturated, probably an effect of upwelling of oxygen poor deep water which had not yet been compensated for by biological production. Three weeks later, the ice edge had retreated in the SIE region and the Chl a concentration had increased three-fold, suggesting the start of a phytoplankton bloom. This was also seen in the oxygen concentration which had increased and showed supersaturation. This coincided with an increased oceanic uptake of CO2 in the SIE during the mesoscale survey.
- Full Text:
- Date Issued: 2004
- Authors: Chierici, M , Fransson, A , Turner, D R , Pakhomov, E A , Froneman, Pierre William
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6847 , http://hdl.handle.net/10962/d1011105
- Description: Underway sampling and measurements of pH, fCO2, oxygen and Chlorophyll a (Chl a) were performed in the surface waters from Cape Town (South Africa) to Queen Maud Land (Antarctica) in the Atlantic sector of the Southern Ocean during the austral summer 1997/1998. From direct measurements of these parameters and from calculated fCO2 the oceanic carbon dioxide system was studied and related to hydrological and biological parameters. fCO2 was in general undersaturated relative to the atmosphere and showed a large variability with values ranging from 313 to 377 μatm with a mean value of 346±13 μatm. The undersaturation was more pronounced in areas associated with fronts where high Chl a and high pH in situ values were observed. Using shipboard wind speed data, estimates of the CO2 flux were made along the transect and during three mesoscale surveys on the northward return transect in the area of the Spring Ice Edge (SIE), the Winter Ice Edge (WIE) and in the Antarctic Polar Front (APF). The undersaturation observed during the transect caused the ocean to act as a sink for CO2 with a mean sea–air flux for the entire transect of −3±5 mmol m−2 d−1 with a large variability between −20 mmol m−2 d−1 (oceanic uptake) to 1.3 mmol m−2 d−1 (oceanic source). The lowest fCO2 values (largest oceanic uptake of CO2) were found at the southern boundary of the APF at 53°S, which coincided with a supersaturation in oxygen and high pH values. Oxygen concentrations were measured from 50°S to 63°S and varied between 324 and 359 μmol kg−1 with a mean value of 347±9 μmol kg−1. In general only small deviations from equilibrium oxygen saturation were observed (mean value=99±2%). However, in the SIE oxygen was clearly undersaturated, probably an effect of upwelling of oxygen poor deep water which had not yet been compensated for by biological production. Three weeks later, the ice edge had retreated in the SIE region and the Chl a concentration had increased three-fold, suggesting the start of a phytoplankton bloom. This was also seen in the oxygen concentration which had increased and showed supersaturation. This coincided with an increased oceanic uptake of CO2 in the SIE during the mesoscale survey.
- Full Text:
- Date Issued: 2004
Concerning secondary thermoluminescence peaks in α-Al_2_O_3_:C
- Authors: Chithambo, Makaiko L
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6793 , http://hdl.handle.net/10962/d1003823
- Description: Thermoluminescence characteristics of two subsidiary glow peaks, one below 100°C and the other above 300°C, have been studied for measurements between 30°C and 500°C in α-Al_2_O_3_:C. The thermoluminescence intensity of the lower temperature peak decreased with storage with a half-life of about 150 s. In contrast, the intensity of the higher temperature peak increased with storage towards some maximum. The peak-temperature of each of the secondary glow peaks was essentially constant with dose, whereas that of the main peak decreased with irradiation. The dose response for the three peaks was similar except for sublinear growth in the higher temperature peak at low dose values. These effects are discussed in terms of changes in the concentration of F+ luminescence precursors brought about by competitive electron retrapping at deep electron-traps or hole-traps. This work refines the physics and application of α-Al_2_O_3_:C luminescence in radiation dosimetry.
- Full Text:
- Date Issued: 2004
- Authors: Chithambo, Makaiko L
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6793 , http://hdl.handle.net/10962/d1003823
- Description: Thermoluminescence characteristics of two subsidiary glow peaks, one below 100°C and the other above 300°C, have been studied for measurements between 30°C and 500°C in α-Al_2_O_3_:C. The thermoluminescence intensity of the lower temperature peak decreased with storage with a half-life of about 150 s. In contrast, the intensity of the higher temperature peak increased with storage towards some maximum. The peak-temperature of each of the secondary glow peaks was essentially constant with dose, whereas that of the main peak decreased with irradiation. The dose response for the three peaks was similar except for sublinear growth in the higher temperature peak at low dose values. These effects are discussed in terms of changes in the concentration of F+ luminescence precursors brought about by competitive electron retrapping at deep electron-traps or hole-traps. This work refines the physics and application of α-Al_2_O_3_:C luminescence in radiation dosimetry.
- Full Text:
- Date Issued: 2004
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
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
Pre-emigration reflections : Afrikaans speakers moving to New Zealand
- De Klerk, Vivian A, Barkhuizen, Gary
- Authors: De Klerk, Vivian A , Barkhuizen, Gary
- Date: 2004
- Language: English
- Type: Article , text
- Identifier: vital:6138 , http://hdl.handle.net/10962/d1011590
- Description: This article reports on the pre-emigration reflections of 15 Afrikaans speakers, all of whom were in the final stages of preparing to emigrate to New Zealand. The study explores the linguistic histories of the participants, their attitudes to their mother tongue (Afrikaans) and to English, and their views on South Africa's language policy and how it has influenced their decisions to leave the country. The paper also offers a view on possible long-term linguistic outcomes for these families.
- Full Text:
- Date Issued: 2004
- Authors: De Klerk, Vivian A , Barkhuizen, Gary
- Date: 2004
- Language: English
- Type: Article , text
- Identifier: vital:6138 , http://hdl.handle.net/10962/d1011590
- Description: This article reports on the pre-emigration reflections of 15 Afrikaans speakers, all of whom were in the final stages of preparing to emigrate to New Zealand. The study explores the linguistic histories of the participants, their attitudes to their mother tongue (Afrikaans) and to English, and their views on South Africa's language policy and how it has influenced their decisions to leave the country. The paper also offers a view on possible long-term linguistic outcomes for these families.
- Full Text:
- Date Issued: 2004
Constructing a cardinal measure of democratic development in a transition polity: the Nigerian example
- Dinneya, Godson E, Tsegaye, Asrat
- Authors: Dinneya, Godson E , Tsegaye, Asrat
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6076 , http://hdl.handle.net/10962/d1003837
- Description: Existing measures of the level of democracy present in a given state treat democracy as a product and therefore place undue emphasis on actual freedoms enjoyed by the citizens of the country. In transition polities where the actual levels of freedom are low despite continuing efforts to democratize, democracy should be seen as a process rather than a product. A measure that dilutes the end product to capture today's struggles against undemocratic structures and policies does so in order to recognize the foundations these inputs lay for future democratic development. Nigeria exemplifies the many polities in transition on the African continent. This essay looks at the major political events that typify the processes of power change, quality of governance, political environment and democratic dividends, and uses them to construct democratization indices to determine the pattern and level of democratization in Nigeria since political independence. This exercise sets the stage for assessing the impacts of various dimensions of democratization on the performance of the Nigerian economy.
- Full Text:
- Date Issued: 2004
- Authors: Dinneya, Godson E , Tsegaye, Asrat
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6076 , http://hdl.handle.net/10962/d1003837
- Description: Existing measures of the level of democracy present in a given state treat democracy as a product and therefore place undue emphasis on actual freedoms enjoyed by the citizens of the country. In transition polities where the actual levels of freedom are low despite continuing efforts to democratize, democracy should be seen as a process rather than a product. A measure that dilutes the end product to capture today's struggles against undemocratic structures and policies does so in order to recognize the foundations these inputs lay for future democratic development. Nigeria exemplifies the many polities in transition on the African continent. This essay looks at the major political events that typify the processes of power change, quality of governance, political environment and democratic dividends, and uses them to construct democratization indices to determine the pattern and level of democratization in Nigeria since political independence. This exercise sets the stage for assessing the impacts of various dimensions of democratization on the performance of the Nigerian economy.
- Full Text:
- Date Issued: 2004
Drimia chalumnensis (Hyacinthaceae - Urgineoideae), a new species from Eastern Cape, South Africa
- Dold, Anthony P, Brink, Estelle
- Authors: Dold, Anthony P , Brink, Estelle
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6516 , http://hdl.handle.net/10962/d1005944
- Description: Drimia chalumnensis, a new inconspicuous dwarf species from the Albany Centre of Floristic Endemism in Eastern Cape, South Africa, is restricted to the coastal plains of the Chalumna river in small scattered aggregated colonies on exposed sandstone sheets in pockets of loose sandy soil. It is distinguished by its capitate inflorescence, separate, petiolate bulb scales, and prostrate, coriaceous, linear-lanceolate leaves with cartilaginous margins.
- Full Text:
- Date Issued: 2004
- Authors: Dold, Anthony P , Brink, Estelle
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6516 , http://hdl.handle.net/10962/d1005944
- Description: Drimia chalumnensis, a new inconspicuous dwarf species from the Albany Centre of Floristic Endemism in Eastern Cape, South Africa, is restricted to the coastal plains of the Chalumna river in small scattered aggregated colonies on exposed sandstone sheets in pockets of loose sandy soil. It is distinguished by its capitate inflorescence, separate, petiolate bulb scales, and prostrate, coriaceous, linear-lanceolate leaves with cartilaginous margins.
- Full Text:
- Date Issued: 2004
Pictograms for conveying medicine instructions: comprehension in various South African language groups
- Dowse, Roslind, Ehlers, Martina S
- Authors: Dowse, Roslind , Ehlers, Martina S
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6354 , http://hdl.handle.net/10962/d1006038
- Description: The comprehension of medicine instructions is essential for the safe and effective use of medicines. In cases where low literacy constitutes a possible barrier to understanding written medicine information fully, the inclusion of pictograms may facilitate comprehension. Twenty-three internationally available pictograms and 23 corresponding locally developed images were evaluated in 304 low-literate respondents from eight different South African language groups. Demographic data were collected and an English literacy test was administered to those respondents who had stated that they could read English. Interviewees were shown the 46 pictograms in random order and were asked for their interpretation. Preference for either the international or local version was assessed. Correct interpretation of individual pictograms ranged from 14% to 97%. Images which had been developed locally were more successful in eliciting correct interpretations than those obtained from an international source (USP pictograms). Only 2 of the 23 USP pictograms achieved the 85% criterion of the American National Standards Institute compared with 12 of 23 locally developed counterparts. Local pictograms were preferred over the American ones in all cases. Standard of education had a significant influence on interpretation, whereas no significant differences in interpretation could be attributed to cultural diversity between the African language groups. Almost all respondents (98%) reacted positively to the idea of having pictograms on their medicine labels. The success of the local pictograms highlighted the value of a rigorous and consultative design and test process. Results from one African language group can reliably be extrapolated to other groups in South Africa.
- Full Text:
- Date Issued: 2004
- Authors: Dowse, Roslind , Ehlers, Martina S
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6354 , http://hdl.handle.net/10962/d1006038
- Description: The comprehension of medicine instructions is essential for the safe and effective use of medicines. In cases where low literacy constitutes a possible barrier to understanding written medicine information fully, the inclusion of pictograms may facilitate comprehension. Twenty-three internationally available pictograms and 23 corresponding locally developed images were evaluated in 304 low-literate respondents from eight different South African language groups. Demographic data were collected and an English literacy test was administered to those respondents who had stated that they could read English. Interviewees were shown the 46 pictograms in random order and were asked for their interpretation. Preference for either the international or local version was assessed. Correct interpretation of individual pictograms ranged from 14% to 97%. Images which had been developed locally were more successful in eliciting correct interpretations than those obtained from an international source (USP pictograms). Only 2 of the 23 USP pictograms achieved the 85% criterion of the American National Standards Institute compared with 12 of 23 locally developed counterparts. Local pictograms were preferred over the American ones in all cases. Standard of education had a significant influence on interpretation, whereas no significant differences in interpretation could be attributed to cultural diversity between the African language groups. Almost all respondents (98%) reacted positively to the idea of having pictograms on their medicine labels. The success of the local pictograms highlighted the value of a rigorous and consultative design and test process. Results from one African language group can reliably be extrapolated to other groups in South Africa.
- Full Text:
- Date Issued: 2004
A Trypanosoma cruzi heat shock protein 40 is able to stimulate the adenosine triphosphate hydrolysis activity of heat shock protein 70 and can substitute for a yeast heat shock protein 40
- Edkins, Adrienne L, Ludewig, M H, Blatch, Gregory L
- Authors: Edkins, Adrienne L , Ludewig, M H , Blatch, Gregory L
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6465 , http://hdl.handle.net/10962/d1005794 , http://dx.doi.org/10.1016/j.biocel.2004.01.016
- Description: The process of assisted protein folding, characteristic of members of the heat shock protein 70 (Hsp70) and heat shock protein 40 (Hsp40) molecular chaperone families, is important for maintaining the structural integrity of cellular protein machinery under normal and stressful conditions. Hsp70 and Hsp40 cooperate to bind non-native protein conformations in a process of adenosine triphosphate (ATP)-regulated assisted protein folding. We have analysed the molecular chaperone activity of the cytoplasmic inducible Hsp70 from Trypanosoma cruzi (TcHsp70) and its interactions with its potential partner Hsp40s (T. cruzi DnaJ protein 1 [Tcj1] and T. cruzi DnaJ protein 2 [Tcj2]). Histidine-tagged TcHsp70 (His-TcHsp70), Tcj1 (Tcj1-His) and Tcj2 (His-Tcj2) were over-produced in Escherichia coli and purified by nickel affinity chromatography. The in vitro basal specific ATP hydrolysis activity (ATPase activity) of His-TcHsp70 was determined as 40 nmol phosphate/min/mg protein, significantly higher than that reported for other Hsp70s. The basal specific ATPase activity was stimulated to a maximal level of 60 nmol phosphate/min/mg protein in the presence of His-Tcj2 and a model substrate, reduced carboxymethylated α-lactalbumin. In vivo complementation assays showed that Tcj2 was able to overcome the temperature sensitivity of the ydj1 mutant Saccharomyces cerevisiae strain JJ160, suggesting that Tcj2 may be functionally equivalent to the yeast Hsp40 homologue (yeast DnaJ protein 1, Ydj1). These data suggest that Tcj2 is involved in cytoprotection in a similar fashion to Ydj1, and that TcHsp70 and Tcj2 may interact in a nucleotide-regulated process of chaperone-assisted protein folding.
- Full Text:
- Date Issued: 2004
- Authors: Edkins, Adrienne L , Ludewig, M H , Blatch, Gregory L
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6465 , http://hdl.handle.net/10962/d1005794 , http://dx.doi.org/10.1016/j.biocel.2004.01.016
- Description: The process of assisted protein folding, characteristic of members of the heat shock protein 70 (Hsp70) and heat shock protein 40 (Hsp40) molecular chaperone families, is important for maintaining the structural integrity of cellular protein machinery under normal and stressful conditions. Hsp70 and Hsp40 cooperate to bind non-native protein conformations in a process of adenosine triphosphate (ATP)-regulated assisted protein folding. We have analysed the molecular chaperone activity of the cytoplasmic inducible Hsp70 from Trypanosoma cruzi (TcHsp70) and its interactions with its potential partner Hsp40s (T. cruzi DnaJ protein 1 [Tcj1] and T. cruzi DnaJ protein 2 [Tcj2]). Histidine-tagged TcHsp70 (His-TcHsp70), Tcj1 (Tcj1-His) and Tcj2 (His-Tcj2) were over-produced in Escherichia coli and purified by nickel affinity chromatography. The in vitro basal specific ATP hydrolysis activity (ATPase activity) of His-TcHsp70 was determined as 40 nmol phosphate/min/mg protein, significantly higher than that reported for other Hsp70s. The basal specific ATPase activity was stimulated to a maximal level of 60 nmol phosphate/min/mg protein in the presence of His-Tcj2 and a model substrate, reduced carboxymethylated α-lactalbumin. In vivo complementation assays showed that Tcj2 was able to overcome the temperature sensitivity of the ydj1 mutant Saccharomyces cerevisiae strain JJ160, suggesting that Tcj2 may be functionally equivalent to the yeast Hsp40 homologue (yeast DnaJ protein 1, Ydj1). These data suggest that Tcj2 is involved in cytoprotection in a similar fashion to Ydj1, and that TcHsp70 and Tcj2 may interact in a nucleotide-regulated process of chaperone-assisted protein folding.
- Full Text:
- Date Issued: 2004
Developing evidence-based practice: the role of case-based research
- Edwards, D J A, Dattilio, F M, Bromley, D B
- Authors: Edwards, D J A , Dattilio, F M , Bromley, D B
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6243 , http://hdl.handle.net/10962/d1007856
- Description: How can practitioners engage in evidence-based practice when the evidence for effectiveness of psychological treatments comes from randomized controlled trials using patient populations different from those encountered in everyday settings and treatment manuals that seem oversimplified and inflexible? The authors argue that important evidence about best practice comes from case-based research, which builds knowledge in a clinically useful manner and complements what is achieved by multivariate research methods. A multidimensional model of the research process is provided that includes clinical practice and case-based research as significant contributors. The authors summarize the principles of case-based research and provide examples of recent technical advances. Finally, the authors suggest ways in which practitioners can apply the case-based approach in researching and publishing their own cases, perhaps in collaboration with university-based researchers.
- Full Text:
- Date Issued: 2004
- Authors: Edwards, D J A , Dattilio, F M , Bromley, D B
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6243 , http://hdl.handle.net/10962/d1007856
- Description: How can practitioners engage in evidence-based practice when the evidence for effectiveness of psychological treatments comes from randomized controlled trials using patient populations different from those encountered in everyday settings and treatment manuals that seem oversimplified and inflexible? The authors argue that important evidence about best practice comes from case-based research, which builds knowledge in a clinically useful manner and complements what is achieved by multivariate research methods. A multidimensional model of the research process is provided that includes clinical practice and case-based research as significant contributors. The authors summarize the principles of case-based research and provide examples of recent technical advances. Finally, the authors suggest ways in which practitioners can apply the case-based approach in researching and publishing their own cases, perhaps in collaboration with university-based researchers.
- Full Text:
- Date Issued: 2004
Spatial structure of recruitment in the mussel Perna perna at local scales: effects of adults, algae and recruit size
- Erlandsson, Johan, McQuaid, Christopher D
- Authors: Erlandsson, Johan , McQuaid, Christopher D
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6898 , http://hdl.handle.net/10962/d1011660
- Description: To test the assumption that there is no spatial structure in small-scale recruitment variability of rocky shore mussels, we examined spatial dependence in the distribution of density of recruits (late plantigrades: 0.5 to 3.5 mm; larger recruits: 3.5 to 10 mm) and adults of the brown mussel Perna perna within local scales (30 lags ranging between 0.35 and 10.5 m) in mid- and upper mussel beds. Spatial heterogeneity was estimated by analyzing scaling properties of semivariograms using a fractal approach. Relationships between density of mussel recruits and adults and biomass of the red alga Gelidium pristoides at the different scales were examined by cross-semivariograms. We found that the distribution of adults showed spatial dependence at all transects, often with higher spatial heterogeneity (higher fractal dimension, D) at smaller scales (1st scaling region). The distribution of larger recruits exhibited spatial dependence at all transects, revealing a spatial structure, which was related to that of adults. In contrast, the distribution of late plantigrades showed mainly spatial independence (random pattern; 1.97 < D ≤ 2). Densities of both size classes of recruits were positively related to those of adults at all transects and scales, but the relationship was stronger for larger recruits than late plantigrades, explaining why there was clearer spatial structure of larger recruits. The relationship with algae was mainly negative for larger recruits, while it tended to be positive at many scales for late plantigrades. Thus, both adult mussels and G. pristoides are suitable habitats for plantigrades, while mussels are the main habitat for larger recruits. This may mean that recruits on algae either die or migrate to mussel clumps at a certain size. This study highlights the importance of recruit size when analyzing recruitment patchiness of mussels, and has implications for sustainable management of P. perna.
- Full Text:
- Date Issued: 2004
- Authors: Erlandsson, Johan , McQuaid, Christopher D
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6898 , http://hdl.handle.net/10962/d1011660
- Description: To test the assumption that there is no spatial structure in small-scale recruitment variability of rocky shore mussels, we examined spatial dependence in the distribution of density of recruits (late plantigrades: 0.5 to 3.5 mm; larger recruits: 3.5 to 10 mm) and adults of the brown mussel Perna perna within local scales (30 lags ranging between 0.35 and 10.5 m) in mid- and upper mussel beds. Spatial heterogeneity was estimated by analyzing scaling properties of semivariograms using a fractal approach. Relationships between density of mussel recruits and adults and biomass of the red alga Gelidium pristoides at the different scales were examined by cross-semivariograms. We found that the distribution of adults showed spatial dependence at all transects, often with higher spatial heterogeneity (higher fractal dimension, D) at smaller scales (1st scaling region). The distribution of larger recruits exhibited spatial dependence at all transects, revealing a spatial structure, which was related to that of adults. In contrast, the distribution of late plantigrades showed mainly spatial independence (random pattern; 1.97 < D ≤ 2). Densities of both size classes of recruits were positively related to those of adults at all transects and scales, but the relationship was stronger for larger recruits than late plantigrades, explaining why there was clearer spatial structure of larger recruits. The relationship with algae was mainly negative for larger recruits, while it tended to be positive at many scales for late plantigrades. Thus, both adult mussels and G. pristoides are suitable habitats for plantigrades, while mussels are the main habitat for larger recruits. This may mean that recruits on algae either die or migrate to mussel clumps at a certain size. This study highlights the importance of recruit size when analyzing recruitment patchiness of mussels, and has implications for sustainable management of P. perna.
- Full Text:
- Date Issued: 2004
‘The Gentle Art of Letting the Other Fellow Have Your Own Way': Viewpoints on a media narrative used to promote the proposed N2 toll road
- Farrington, Katie, Davies, Kate
- Authors: Farrington, Katie , Davies, Kate
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6098 , http://hdl.handle.net/10962/d1008628
- Description: This viewpoint paper is written in response to a South African National Roads Agency (SANRAL) advertorial published in various South African regional newspapers in February 2004. We highlight the importance of developing ‘media literacy’ – reading skills which enable the critical deconstruction of media texts. We explore, more specifically, the public relations strategies used by large corporations, and the media’s role as disseminators of corporate marketing material.We also look at the relevance in identifying the language and discourse positioning the writer, photographer, reader and their choice representative medium.
- Full Text:
- Date Issued: 2004
- Authors: Farrington, Katie , Davies, Kate
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6098 , http://hdl.handle.net/10962/d1008628
- Description: This viewpoint paper is written in response to a South African National Roads Agency (SANRAL) advertorial published in various South African regional newspapers in February 2004. We highlight the importance of developing ‘media literacy’ – reading skills which enable the critical deconstruction of media texts. We explore, more specifically, the public relations strategies used by large corporations, and the media’s role as disseminators of corporate marketing material.We also look at the relevance in identifying the language and discourse positioning the writer, photographer, reader and their choice representative medium.
- Full Text:
- Date Issued: 2004