New and improved : Linda in Java
- Authors: Wells, George C
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6613 , http://hdl.handle.net/10962/d1011511 , http://www.sciencedirect.com/science/article/pii/S0167642305000869
- Description: This paper discusses the current resurgence of interest in the Linda coordination language for parallel and distributed programming. Particularly in the Java field, there have been a number of developments over the past few years. These developments are summarised together with the advantages of using Linda for programming concurrent systems. Some problems with the basic Linda approach are also discussed and a novel solution to these is presented. The power and flexibility of the proposed extensions to the Linda programming model are illustrated by considering a number of example applications, including a detailed case study of visual language parsing.
- Full Text:
- Authors: Wells, George C
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6613 , http://hdl.handle.net/10962/d1011511 , http://www.sciencedirect.com/science/article/pii/S0167642305000869
- Description: This paper discusses the current resurgence of interest in the Linda coordination language for parallel and distributed programming. Particularly in the Java field, there have been a number of developments over the past few years. These developments are summarised together with the advantages of using Linda for programming concurrent systems. Some problems with the basic Linda approach are also discussed and a novel solution to these is presented. The power and flexibility of the proposed extensions to the Linda programming model are illustrated by considering a number of example applications, including a detailed case study of visual language parsing.
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Estimating rainfall and water balance over the Okavango River Basin for hydrological applications
- Wilk, J, Kniveton, D, Andersson, L, Layberry, R, Todd, M C, Hughes, Denis A
- Authors: Wilk, J , Kniveton, D , Andersson, L , Layberry, R , Todd, M C , Hughes, Denis A
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7084 , http://hdl.handle.net/10962/d1012343 , http://dx.doi.org/10.1016/j.jhydrol.2006.04.049
- Description: A historical database for use in rainfall-runoff modeling of the Okavango River Basin in Southwest Africa is presented. The work has relevance for similar data-sparse regions. The parameters of main concern are rainfall and catchment water balance, which are key variables for subsequent studies of the hydrological impacts of development and climate change. Rainfall estimates are based on a combination of in situ gauges and satellite sources. Rain gauge measurements are most extensive from 1955 to 1972, after which they are drastically reduced due to the Angolan civil war. The sensitivity of the rainfall fields to spatial interpolation techniques and the density of gauges were evaluated. Satellite based rainfall estimates for the basin are developed for the period from 1991 onwards, based on the Tropical Rainfall Measuring Mission (TRMM) and Special Sensor Microwave Imager (SSM/I) datasets. The consistency between the gauges and satellite estimates was considered. A methodology was developed to allow calibration of the rainfall-runoff hydrological model against rain gauge data from 1960 to 1972, with the prerequisite that the model should be driven by satellite derived rainfall products from 1990 onwards. With the rain gauge data, addition of a single rainfall station (Longa) in regions where stations earlier were lacking was more important than the chosen interpolation method. Comparison of satellite and gauge rainfall outside the basin indicated that the satellite overestimates rainfall by 20%. A non-linear correction was derived by fitting the rainfall frequency characteristics to those of the historical rainfall data. This satellite rainfall dataset was found satisfactory when using the Pitman rainfall-runoff model (Hughes, D., Andersson, L., Wilk, J., Savenije, H.H.G., this issue. Regional calibration of the Pitman model for the Okavango River. Journal of Hydrology). Intensive monitoring in the region is recommended to increase accuracy of the comprehensive satellite rainfall estimate calibration procedure.
- Full Text:
- Authors: Wilk, J , Kniveton, D , Andersson, L , Layberry, R , Todd, M C , Hughes, Denis A
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7084 , http://hdl.handle.net/10962/d1012343 , http://dx.doi.org/10.1016/j.jhydrol.2006.04.049
- Description: A historical database for use in rainfall-runoff modeling of the Okavango River Basin in Southwest Africa is presented. The work has relevance for similar data-sparse regions. The parameters of main concern are rainfall and catchment water balance, which are key variables for subsequent studies of the hydrological impacts of development and climate change. Rainfall estimates are based on a combination of in situ gauges and satellite sources. Rain gauge measurements are most extensive from 1955 to 1972, after which they are drastically reduced due to the Angolan civil war. The sensitivity of the rainfall fields to spatial interpolation techniques and the density of gauges were evaluated. Satellite based rainfall estimates for the basin are developed for the period from 1991 onwards, based on the Tropical Rainfall Measuring Mission (TRMM) and Special Sensor Microwave Imager (SSM/I) datasets. The consistency between the gauges and satellite estimates was considered. A methodology was developed to allow calibration of the rainfall-runoff hydrological model against rain gauge data from 1960 to 1972, with the prerequisite that the model should be driven by satellite derived rainfall products from 1990 onwards. With the rain gauge data, addition of a single rainfall station (Longa) in regions where stations earlier were lacking was more important than the chosen interpolation method. Comparison of satellite and gauge rainfall outside the basin indicated that the satellite overestimates rainfall by 20%. A non-linear correction was derived by fitting the rainfall frequency characteristics to those of the historical rainfall data. This satellite rainfall dataset was found satisfactory when using the Pitman rainfall-runoff model (Hughes, D., Andersson, L., Wilk, J., Savenije, H.H.G., this issue. Regional calibration of the Pitman model for the Okavango River. Journal of Hydrology). Intensive monitoring in the region is recommended to increase accuracy of the comprehensive satellite rainfall estimate calibration procedure.
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Recruitment behaviour in the ponerine ant, Plectroctena mandibularis F. Smith (Hymenoptera: Formicidae)
- Wilkins, K J, Harman, K, Villet, Martin H
- Authors: Wilkins, K J , Harman, K , Villet, Martin H
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6887 , http://hdl.handle.net/10962/d1011647
- Description: Although workers of Plectroctena mandibularis laid trails with their stings while foraging, the trails appeared to be for individual orientation, because they never recruited nestmates to prey. However, both workers and queens laid trails when recruiting nestmates of either caste to new nest sites. During trail-laying, fluted hairs on the posterior edge of tergite VI were dragged along the ground, presumably applying a pheromone to the substrate. Anatomical and behavioural evidence suggests that pygidial gland secretions moved from the intersegmental pygidial gland between tergites VI and VII into a fingerprint-like, lamellar cuticular reservoir on the pygidium, and from there via the hairs to the substrate. These results suggest that recruitment may be crucial to moving nests but of value only to certain types of foraging, and that recruitment might even have originated in the Formicidae in the context of colony relocation, and then secondarily evolved to assist foraging.
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- Authors: Wilkins, K J , Harman, K , Villet, Martin H
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6887 , http://hdl.handle.net/10962/d1011647
- Description: Although workers of Plectroctena mandibularis laid trails with their stings while foraging, the trails appeared to be for individual orientation, because they never recruited nestmates to prey. However, both workers and queens laid trails when recruiting nestmates of either caste to new nest sites. During trail-laying, fluted hairs on the posterior edge of tergite VI were dragged along the ground, presumably applying a pheromone to the substrate. Anatomical and behavioural evidence suggests that pygidial gland secretions moved from the intersegmental pygidial gland between tergites VI and VII into a fingerprint-like, lamellar cuticular reservoir on the pygidium, and from there via the hairs to the substrate. These results suggest that recruitment may be crucial to moving nests but of value only to certain types of foraging, and that recruitment might even have originated in the Formicidae in the context of colony relocation, and then secondarily evolved to assist foraging.
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A history of southern African research relevant to forensic entomology
- Williams, K A, Villet, Martin H
- Authors: Williams, K A , Villet, Martin H
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6909 , http://hdl.handle.net/10962/d1011862
- Description: Entomological forensic evidence has been used in southern Africa for decades but explicitly forensic research began in southern Africa only 26 years ago. Although applicable local research has accumulated since 1921, it is scattered in a diverse literature or unpublished. Some overseas research has also touched on local species. This review uses a historical approach to synthesize the southern African literature and to illustrate the cross-disciplinary, opportunistic nature of forensic entomology. Distinct phases of research focused on agriculture (1921-1950), medicine (1952- 1965), ecology (1968-1990) and forensics (1980-2005), but systematics spanned the entire period and tended to be ad hoc. Few scientists were involved, situated at geographically distant locations and with widely disparate research interests. The review concludes with an overview of southern African entomologists who have been involved in medico-legal investigations, and a critical evaluation of the past and future of the discipline locally.
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- Authors: Williams, K A , Villet, Martin H
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6909 , http://hdl.handle.net/10962/d1011862
- Description: Entomological forensic evidence has been used in southern Africa for decades but explicitly forensic research began in southern Africa only 26 years ago. Although applicable local research has accumulated since 1921, it is scattered in a diverse literature or unpublished. Some overseas research has also touched on local species. This review uses a historical approach to synthesize the southern African literature and to illustrate the cross-disciplinary, opportunistic nature of forensic entomology. Distinct phases of research focused on agriculture (1921-1950), medicine (1952- 1965), ecology (1968-1990) and forensics (1980-2005), but systematics spanned the entire period and tended to be ad hoc. Few scientists were involved, situated at geographically distant locations and with widely disparate research interests. The review concludes with an overview of southern African entomologists who have been involved in medico-legal investigations, and a critical evaluation of the past and future of the discipline locally.
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Book review: Derek Barker: English Academic Literary Discourse in South Africa 1958-2004: A Review of 11 Academic Journals
- Authors: Wright, Laurence
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7044 , http://hdl.handle.net/10962/d1007386
- Description: Barker’s book concerns the evolution and publishing trajectories of South African journals devoted to English literary studies between the years 1958 (when the first such journal, English Studies in Africa, came into being) and 2004, the end-date of the survey. In other words, his work coincides with the period in South African history when apartheid’s protagonists were pushing for total political and social ascendancy through to the nation’s emergence into the arena of democratic possibility.
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- Authors: Wright, Laurence
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7044 , http://hdl.handle.net/10962/d1007386
- Description: Barker’s book concerns the evolution and publishing trajectories of South African journals devoted to English literary studies between the years 1958 (when the first such journal, English Studies in Africa, came into being) and 2004, the end-date of the survey. In other words, his work coincides with the period in South African history when apartheid’s protagonists were pushing for total political and social ascendancy through to the nation’s emergence into the arena of democratic possibility.
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Repositioning Renaissance studies in South Africa: strategic thinking or 'business-as-usual
- Authors: Wright, Laurence
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7054 , http://hdl.handle.net/10962/d1007415
- Description: Increasingly, in many leading South African tertiary departments of literature, early modern studies have a fairly slim hold on the core curriculum. More and more, departmental offerings concentrate on nineteenth and twentieth century literature, perhaps in the belief either that today’s students are so poorly prepared that they will never be able to cope with the mental shifts necessary to appreciate pre-industrial literature and its language, or, worse, that nothing before the C19 colonial incursion into South Africa can really matter very much to undergraduates. Whatever the reason, in such departments, it is no longer possible to get to grips with the contribution of the renaissance to the formation of the modern world. The significance of the broader nomenclature, early modern studies, doesn’t appear to strike home, especially the point that, if students want to understand the world we live in, they have to know this period particularly well. Indeed, they need to have some idea of the interaction between early modern Europe and the literature and ideas of the ancient civilizations of Rome and Greece. If we fail them in this regard, as I believe we are doing to an increasing extent, the result will be generations of intellectual sleepwalkers, denizens of mental landscapes they are responding to, or ‘reading’, in terms of an inner life unaware of important historical continuities and disjunctions; cut off, moreover, from understanding essential features of modernity.
- Full Text:
- Authors: Wright, Laurence
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7054 , http://hdl.handle.net/10962/d1007415
- Description: Increasingly, in many leading South African tertiary departments of literature, early modern studies have a fairly slim hold on the core curriculum. More and more, departmental offerings concentrate on nineteenth and twentieth century literature, perhaps in the belief either that today’s students are so poorly prepared that they will never be able to cope with the mental shifts necessary to appreciate pre-industrial literature and its language, or, worse, that nothing before the C19 colonial incursion into South Africa can really matter very much to undergraduates. Whatever the reason, in such departments, it is no longer possible to get to grips with the contribution of the renaissance to the formation of the modern world. The significance of the broader nomenclature, early modern studies, doesn’t appear to strike home, especially the point that, if students want to understand the world we live in, they have to know this period particularly well. Indeed, they need to have some idea of the interaction between early modern Europe and the literature and ideas of the ancient civilizations of Rome and Greece. If we fail them in this regard, as I believe we are doing to an increasing extent, the result will be generations of intellectual sleepwalkers, denizens of mental landscapes they are responding to, or ‘reading’, in terms of an inner life unaware of important historical continuities and disjunctions; cut off, moreover, from understanding essential features of modernity.
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Sand stress as a non-determinant of habitat segregation of indigenous (Perna perna) and invasive (Mytilus galloprovincialis) mussels in South Africa
- Zardi, Gerardo I, Nicastro, Katy R, Porri, Francesca, McQuaid, Christopher D
- Authors: Zardi, Gerardo I , Nicastro, Katy R , Porri, Francesca , McQuaid, Christopher D
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6946 , http://hdl.handle.net/10962/d1011974
- Description: Periodical sand inundation influences diversity and distribution of intertidal species throughout the world. This study investigates the effect of sand stress on survival and on habitat segregation of the two dominant mussel species living in South Africa, the invasive Mytilus galloprovincialis and the indigenous Perna perna. P. perna occupies a lower intertidal zone which, monthly surveys over 1.5 years showed, is covered by sand for longer periods than the higher M. galloprovincialis zone. Despite this, when buried under sand, P. perna mortality rates were significantly higher than those of M. galloprovincialis in both laboratory and in field experiments. Under anoxic condition, P. perna mortality rates were still significantly higher than those for M. galloprovincialis, but both species died later than when exposed to sand burial, underlining the importance of the physical action of sand on mussel internal organs. When buried, both species accumulate sediments within the shell valves while still alive, but the quantities are much greater for P. perna. This suggests that P. perna gills are more severely damaged by sand abrasion and could explain its higher mortality rates. M. galloprovincialis has longer labial palps than P. perna, indicating a higher particle sorting ability and consequently explaining its lower mortality rates when exposed to sand in suspension. Habitat segregation is often explained by physiological tolerances, but in this case, such explanations fail. Although sand stress strongly affects the survival of the two species, it does not explain their vertical zonation. Contrary to our expectations, the species that is less well adapted to cope with sand stress maintains dominance in a habitat where such stress is high.
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- Authors: Zardi, Gerardo I , Nicastro, Katy R , Porri, Francesca , McQuaid, Christopher D
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6946 , http://hdl.handle.net/10962/d1011974
- Description: Periodical sand inundation influences diversity and distribution of intertidal species throughout the world. This study investigates the effect of sand stress on survival and on habitat segregation of the two dominant mussel species living in South Africa, the invasive Mytilus galloprovincialis and the indigenous Perna perna. P. perna occupies a lower intertidal zone which, monthly surveys over 1.5 years showed, is covered by sand for longer periods than the higher M. galloprovincialis zone. Despite this, when buried under sand, P. perna mortality rates were significantly higher than those of M. galloprovincialis in both laboratory and in field experiments. Under anoxic condition, P. perna mortality rates were still significantly higher than those for M. galloprovincialis, but both species died later than when exposed to sand burial, underlining the importance of the physical action of sand on mussel internal organs. When buried, both species accumulate sediments within the shell valves while still alive, but the quantities are much greater for P. perna. This suggests that P. perna gills are more severely damaged by sand abrasion and could explain its higher mortality rates. M. galloprovincialis has longer labial palps than P. perna, indicating a higher particle sorting ability and consequently explaining its lower mortality rates when exposed to sand in suspension. Habitat segregation is often explained by physiological tolerances, but in this case, such explanations fail. Although sand stress strongly affects the survival of the two species, it does not explain their vertical zonation. Contrary to our expectations, the species that is less well adapted to cope with sand stress maintains dominance in a habitat where such stress is high.
- Full Text: