“As soon as the four sides are all equal, then the angles must be 90° each”: children's misconceptions in geometry
- Atebe, Humphrey U, Schäfer, Marc
- Authors: Atebe, Humphrey U , Schäfer, Marc
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140983 , vital:37934 , DOI: 10.1080/10288457.2008.10740634
- Description: This study describes Nigerian and South African students' conceptual understanding in high school geometry based on the van Hiele model of geometric thinking levels. The study further highlights students' misconceptions in school geometry. Concepts of triangles and quadrilaterals were investigated among 36 mathematics learners drawn from grades 10 through 12 who participated in this study. The tasks included identifying and naming shapes, sorting of shapes, stating the properties of shapes, defining of shapes and establishing class inclusions of shapes. The results indicated that many Nigerian and South African high school learners in Grade 10, 11 and 12 hold a number of misconceptions about geometric concepts of triangles and quadrilaterals.
- Full Text:
- Date Issued: 2013
- Authors: Atebe, Humphrey U , Schäfer, Marc
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140983 , vital:37934 , DOI: 10.1080/10288457.2008.10740634
- Description: This study describes Nigerian and South African students' conceptual understanding in high school geometry based on the van Hiele model of geometric thinking levels. The study further highlights students' misconceptions in school geometry. Concepts of triangles and quadrilaterals were investigated among 36 mathematics learners drawn from grades 10 through 12 who participated in this study. The tasks included identifying and naming shapes, sorting of shapes, stating the properties of shapes, defining of shapes and establishing class inclusions of shapes. The results indicated that many Nigerian and South African high school learners in Grade 10, 11 and 12 hold a number of misconceptions about geometric concepts of triangles and quadrilaterals.
- Full Text:
- Date Issued: 2013
A global study of forensically significant calliphorids: implications for identification
- Harvey, M L, Gaudieri, S, Villet, Martin H, Dadour, I R
- Authors: Harvey, M L , Gaudieri, S , Villet, Martin H , Dadour, I R
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6863 , http://hdl.handle.net/10962/d1011156
- Description: A proliferation of molecular studies of the forensically significant Calliphoridae in the last decade has seen molecule-based identification of immature and damaged specimens become a routine complement to traditional morphological identification as a preliminary to the accurate estimation of post-mortem intervals (PMI), which depends on the use of species-specific developmental data. Published molecular studies have tended to focus on generating data for geographically localised communities of species of importance, which has limited the consideration of intraspecific variation in species of global distribution. This study used phylogenetic analysis to assess the species status of 27 forensically important calliphorid species based on 1167 base pairs of the COI gene of 119 specimens from 22 countries, and confirmed the utility of the COI gene in identifying most species. The species Lucilia cuprina, Chrysomya megacephala, Ch. saffranea, Ch. albifrontalis and Calliphora stygia were unable to be monophyletically resolved based on these data. Identification of phylogenetically young species will require a faster-evolving molecular marker, but most species could be unambiguously characterised by sampling relatively few conspecific individuals if they were from distant localities. Intraspecific geographical variation was observed within Ch. rufifacies and L. cuprina, and is discussed with reference to unrecognised species.
- Full Text:
- Date Issued: 2008
- Authors: Harvey, M L , Gaudieri, S , Villet, Martin H , Dadour, I R
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6863 , http://hdl.handle.net/10962/d1011156
- Description: A proliferation of molecular studies of the forensically significant Calliphoridae in the last decade has seen molecule-based identification of immature and damaged specimens become a routine complement to traditional morphological identification as a preliminary to the accurate estimation of post-mortem intervals (PMI), which depends on the use of species-specific developmental data. Published molecular studies have tended to focus on generating data for geographically localised communities of species of importance, which has limited the consideration of intraspecific variation in species of global distribution. This study used phylogenetic analysis to assess the species status of 27 forensically important calliphorid species based on 1167 base pairs of the COI gene of 119 specimens from 22 countries, and confirmed the utility of the COI gene in identifying most species. The species Lucilia cuprina, Chrysomya megacephala, Ch. saffranea, Ch. albifrontalis and Calliphora stygia were unable to be monophyletically resolved based on these data. Identification of phylogenetically young species will require a faster-evolving molecular marker, but most species could be unambiguously characterised by sampling relatively few conspecific individuals if they were from distant localities. Intraspecific geographical variation was observed within Ch. rufifacies and L. cuprina, and is discussed with reference to unrecognised species.
- Full Text:
- Date Issued: 2008
Beneficial effects of medicinal plants in fish diseases
- Stratev, Deyan, Zhelyazkov, Georgi, Noundou, Xavier Siwe, Krause, Rui W M
- Authors: Stratev, Deyan , Zhelyazkov, Georgi , Noundou, Xavier Siwe , Krause, Rui W M
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123487 , vital:35447 , https://doi.org/10.1007/s10499-017-0219-x
- Description: Fish are constantly in contact with pathogens inhabiting water. High population density as well as poor hydrodynamic conditions and feeding lead to an increased sensitivity towards infections. In order to prevent major economic losses due to diseases, various medications are used for treatment and prevention of infections. The use of antimicrobial drugs in aquacultures could lead to emergence of resistance in pathogenic microorganisms. Alternatives are being sought over the last few years to replace antibiotics, and medicinal plants are one of available options for this purpose. These plants are rich in secondary metabolites and phytochemical compounds, which have an effect against viral, bacterial, and parasitic diseases in fish. Their main advantage is their natural origin and most of these plants do not represent threat for human health, the fish, and the environment. The goal of this review is to present information on the treatment of viral, bacterial, and parasitic diseases in fish through medicinal plants, with focus on the mechanisms of action of the identified secondary metabolites, fractions, or plant extracts.
- Full Text:
- Date Issued: 2008
- Authors: Stratev, Deyan , Zhelyazkov, Georgi , Noundou, Xavier Siwe , Krause, Rui W M
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123487 , vital:35447 , https://doi.org/10.1007/s10499-017-0219-x
- Description: Fish are constantly in contact with pathogens inhabiting water. High population density as well as poor hydrodynamic conditions and feeding lead to an increased sensitivity towards infections. In order to prevent major economic losses due to diseases, various medications are used for treatment and prevention of infections. The use of antimicrobial drugs in aquacultures could lead to emergence of resistance in pathogenic microorganisms. Alternatives are being sought over the last few years to replace antibiotics, and medicinal plants are one of available options for this purpose. These plants are rich in secondary metabolites and phytochemical compounds, which have an effect against viral, bacterial, and parasitic diseases in fish. Their main advantage is their natural origin and most of these plants do not represent threat for human health, the fish, and the environment. The goal of this review is to present information on the treatment of viral, bacterial, and parasitic diseases in fish through medicinal plants, with focus on the mechanisms of action of the identified secondary metabolites, fractions, or plant extracts.
- Full Text:
- Date Issued: 2008
Industrial relations in Namibia since independence: between neo-liberalism and neo-corporatism?
- Authors: Klerck, Gilton
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6320 , http://hdl.handle.net/10962/d1011314
- Description: The paper seeks to examine the changes and continuities in industrial relations in post-independence Namibia. In particular, it aims to explore some of the key elements in the process through which the distribution of the costs and rewards of economic and industrial restructuring is institutionalised. The paper concentrates, through in-depth interviews with key role players, on how the attempts at sustaining a durable and redistributive trade-off between economic efficiency and social equality led to a contradictory fusion of neo-liberal and neo-corporatist forms of labour market regulation. The research reveals that changes in the regulation of the labour market since independence have created opportunities for advancement and participation by groups of more skilled and organised employees, while weaker and less skilled groups have generally experienced a decline in employment conditions and the absence of collective representation. These developments reflect and reproduce patterns of racial and gender discrimination, industrial structure, trade union membership and collective bargaining across the various sectors and occupations. The paper shows that a system of low-skill, low-wage and low-trust relations - with an emphasis on cost reduction and employment "flexibility" - is fast becoming embedded in industrial relations in Namibia. Given the prevailing economic policies, industrial strategies and labour market structures, Namibia's integration into the global economy will most likely involve the increasing dislocation and exclusion of vulnerable and "peripheral" workers from the formal economy. The paper highlights the ways in which the transformation of industrial relations in Namibia is shaped by the legacy of apartheid-colonialism and the pressures of globalisation. Specifically, the conjunction of increasingly deregulated product markets and increasingly regulated labour markets has driven a wedge between the pursuit of short-term objectives and the attainment of long-term transformational goals.
- Full Text:
- Date Issued: 2008
- Authors: Klerck, Gilton
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6320 , http://hdl.handle.net/10962/d1011314
- Description: The paper seeks to examine the changes and continuities in industrial relations in post-independence Namibia. In particular, it aims to explore some of the key elements in the process through which the distribution of the costs and rewards of economic and industrial restructuring is institutionalised. The paper concentrates, through in-depth interviews with key role players, on how the attempts at sustaining a durable and redistributive trade-off between economic efficiency and social equality led to a contradictory fusion of neo-liberal and neo-corporatist forms of labour market regulation. The research reveals that changes in the regulation of the labour market since independence have created opportunities for advancement and participation by groups of more skilled and organised employees, while weaker and less skilled groups have generally experienced a decline in employment conditions and the absence of collective representation. These developments reflect and reproduce patterns of racial and gender discrimination, industrial structure, trade union membership and collective bargaining across the various sectors and occupations. The paper shows that a system of low-skill, low-wage and low-trust relations - with an emphasis on cost reduction and employment "flexibility" - is fast becoming embedded in industrial relations in Namibia. Given the prevailing economic policies, industrial strategies and labour market structures, Namibia's integration into the global economy will most likely involve the increasing dislocation and exclusion of vulnerable and "peripheral" workers from the formal economy. The paper highlights the ways in which the transformation of industrial relations in Namibia is shaped by the legacy of apartheid-colonialism and the pressures of globalisation. Specifically, the conjunction of increasingly deregulated product markets and increasingly regulated labour markets has driven a wedge between the pursuit of short-term objectives and the attainment of long-term transformational goals.
- Full Text:
- Date Issued: 2008
Marginalisation and demographic change in the semi-arid Karoo, South Africa
- Nel, Etienne L, Hill, Trevor R
- Authors: Nel, Etienne L , Hill, Trevor R
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6719 , http://hdl.handle.net/10962/d1006792
- Description: Semi-arid areas are often considered to be environmentally and economically marginal, a situation which has been exacerbated by economic change, shifts in agricultural production and land use, and changing state policy. These themes are explored with reference to a semi-arid landscape, namely the Karoo, which covers some 40% of the geographic space of South Africa and is used primarily for extensive livestock farming. Despite long-term decline in agricultural output, the traditional mainstay of the region, and weakening small town economies, the Karoo's population and the economies of its largest service centres are growing. There are, real socio-economic needs and development backlogs, and the situation has been exacerbated by recent political marginalisation. In this study, the small towns of the region are focal points of investigation and provide a lens to investigate the changing demographic and economic dynamics of the Karoo. Most of the region's population lives in these centres which are service, collection, and distribution points for what traditionally has been an agriculture-based regional economy. This paper explores the concept of marginalisation with specific reference to historical, economic, and demographic change.
- Full Text:
- Date Issued: 2008
- Authors: Nel, Etienne L , Hill, Trevor R
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6719 , http://hdl.handle.net/10962/d1006792
- Description: Semi-arid areas are often considered to be environmentally and economically marginal, a situation which has been exacerbated by economic change, shifts in agricultural production and land use, and changing state policy. These themes are explored with reference to a semi-arid landscape, namely the Karoo, which covers some 40% of the geographic space of South Africa and is used primarily for extensive livestock farming. Despite long-term decline in agricultural output, the traditional mainstay of the region, and weakening small town economies, the Karoo's population and the economies of its largest service centres are growing. There are, real socio-economic needs and development backlogs, and the situation has been exacerbated by recent political marginalisation. In this study, the small towns of the region are focal points of investigation and provide a lens to investigate the changing demographic and economic dynamics of the Karoo. Most of the region's population lives in these centres which are service, collection, and distribution points for what traditionally has been an agriculture-based regional economy. This paper explores the concept of marginalisation with specific reference to historical, economic, and demographic change.
- Full Text:
- Date Issued: 2008
Rock magnetic stratigraphy of a mafic layered sill: a key to the Karoo volcanics plumbing system
- Maes, S M, Ferré, E E, Tikoff, B, Brown, P E, Marsh, Julian S
- Authors: Maes, S M , Ferré, E E , Tikoff, B , Brown, P E , Marsh, Julian S
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144901 , vital:38389 , https://doi.org/10.1016/j.jvolgeores.2005.07.038
- Description: The Insizwa sill is an 1 km-thick subhorizontal layered mafic intrusion and part of the Karoo Large Igneous Province in South Africa. This well-exposed intrusion consists of several superimposed petrologically and geochemically distinct units. Magnetic methods were used to study the intrusion in order to constrain the physical processes active in these types of bodies during crystallization. Rock magnetism studies indicate that within different petrologic units bulk susceptibility is controlled by primary magnetite (with minor pyrrhotite) and/or paramagnetic minerals (olivine, pyroxene). New magnetic data based on 659 specimens obtained from 3 vertical borehole cores, each spaced 5 km apart, confirm the prominent vertical zonation in low field magnetic susceptibility (Klf), degree of anisotropy (Pj) and orientation of the anisotropy of magnetic susceptibility (AMS) axes.
- Full Text:
- Date Issued: 2008
- Authors: Maes, S M , Ferré, E E , Tikoff, B , Brown, P E , Marsh, Julian S
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144901 , vital:38389 , https://doi.org/10.1016/j.jvolgeores.2005.07.038
- Description: The Insizwa sill is an 1 km-thick subhorizontal layered mafic intrusion and part of the Karoo Large Igneous Province in South Africa. This well-exposed intrusion consists of several superimposed petrologically and geochemically distinct units. Magnetic methods were used to study the intrusion in order to constrain the physical processes active in these types of bodies during crystallization. Rock magnetism studies indicate that within different petrologic units bulk susceptibility is controlled by primary magnetite (with minor pyrrhotite) and/or paramagnetic minerals (olivine, pyroxene). New magnetic data based on 659 specimens obtained from 3 vertical borehole cores, each spaced 5 km apart, confirm the prominent vertical zonation in low field magnetic susceptibility (Klf), degree of anisotropy (Pj) and orientation of the anisotropy of magnetic susceptibility (AMS) axes.
- Full Text:
- Date Issued: 2008
School principals' perceptions of team management : a multiple case-study of secondary schools
- Van der Mescht, Hennie, Tyala, Zakunzima
- Authors: Van der Mescht, Hennie , Tyala, Zakunzima
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6105 , http://hdl.handle.net/10962/d1009732
- Description: The notion of school management through teams (team management), though not a new phenomenon in South Africa, was formalized after the advent of democracy in 1994 and the subsequent reorganization of the education system. The concept was subsequently fleshed out in official documentation where the composition and roles of school management teams (SMTs) were elaborated upon. The notion of team management is rooted in theories that stress participation, notably site-based (school-based) management, teamwork, and distributed leadership. We report on a study in which the perceptions of secondary school principals, in Grahamstown, South Africa, of team management were explored. The study was interpretive in orientation, and utilized qualitative data gathering techniques in all (ten) of the state-aided secondary schools in Grahamstown in the Eastern Cape province. We found that, while team management was generally welcomed and even celebrated by principals, there were fundamental tensions surrounding principals' understanding of their leadership roles in a team context. We consider the implications of these findings for leadership development in the context of team management.
- Full Text:
- Date Issued: 2008
- Authors: Van der Mescht, Hennie , Tyala, Zakunzima
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6105 , http://hdl.handle.net/10962/d1009732
- Description: The notion of school management through teams (team management), though not a new phenomenon in South Africa, was formalized after the advent of democracy in 1994 and the subsequent reorganization of the education system. The concept was subsequently fleshed out in official documentation where the composition and roles of school management teams (SMTs) were elaborated upon. The notion of team management is rooted in theories that stress participation, notably site-based (school-based) management, teamwork, and distributed leadership. We report on a study in which the perceptions of secondary school principals, in Grahamstown, South Africa, of team management were explored. The study was interpretive in orientation, and utilized qualitative data gathering techniques in all (ten) of the state-aided secondary schools in Grahamstown in the Eastern Cape province. We found that, while team management was generally welcomed and even celebrated by principals, there were fundamental tensions surrounding principals' understanding of their leadership roles in a team context. We consider the implications of these findings for leadership development in the context of team management.
- Full Text:
- Date Issued: 2008
Tracing and erasure in Kathryn Smith's Psychogeographies: the washing away of wrongs
- Authors: de Jager, Maureen
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147413 , vital:38634 , https://0-hdl.handle.net.wam.seals.ac.za/10520/EJC31057
- Description: Kathryn Smith's Psychogeographies: The Washing Away of Wrongs is a series of twelve prints comprising photographs and handwritten text, wherein she records her 'pilgrimage' to the former homes of British serial killer Dennis Nilsen. As such, it utilises photographic and autographic traces to 'track' the elusive traces left by Nilsen. Given the lapse of two decades between Nilsen's arrest and Smith's visit, the traces of Nilsen's 'wrongs' seem all but erased by the banal façade of suburban living which has continued on, regardless. In taking this as a starting point, the following article considers the motif of absence that characterises Smith's work as intrinsic to traces per se.
- Full Text:
- Date Issued: 2008
- Authors: de Jager, Maureen
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147413 , vital:38634 , https://0-hdl.handle.net.wam.seals.ac.za/10520/EJC31057
- Description: Kathryn Smith's Psychogeographies: The Washing Away of Wrongs is a series of twelve prints comprising photographs and handwritten text, wherein she records her 'pilgrimage' to the former homes of British serial killer Dennis Nilsen. As such, it utilises photographic and autographic traces to 'track' the elusive traces left by Nilsen. Given the lapse of two decades between Nilsen's arrest and Smith's visit, the traces of Nilsen's 'wrongs' seem all but erased by the banal façade of suburban living which has continued on, regardless. In taking this as a starting point, the following article considers the motif of absence that characterises Smith's work as intrinsic to traces per se.
- Full Text:
- Date Issued: 2008
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