Invaded habitat incompatibility affects the suitability of the potential biological control agent Listronotus sordidus for Sagittaria platyphylla in South Africa
- Authors: Martin, Grant D , Coetzee, Julie A , Lloyd, Melissa , Nombewu, Sinoxolo E , Ndlovu, Mpilonhle S , Kwong, Raelene M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103926 , vital:32323 , https://doi.org/10.1080/09583157.2018.1460314
- Description: Sagittaria platyphylla (Engelmann) J.G. Smith (Alismataceae) was first recorded in South Africa in 2008 and is considered to be an emerging weed with naturalised populations occurring throughout the country. A biological control programme was initiated in Australia and surveys conducted between 2010 and 2012 yielded potential agents, including the crown feeding weevil, Listronotus sordidus Gyllenhal (Coleoptera: Curculionidae). The potential of L. sordidus as a candidate biological control agent against S. platyphylla in South Africa was examined. Although adult feeding was recorded on a number of plant species, oviposition and larval development indicated a narrow host range restricted to the Alismataceae. In South Africa, S. platyphylla populations are primarily found in inundated systems. However, laboratory studies showed that L. sordidus did not oviposit on inundated plants, potentially nullifying the impact of the insect on South African populations. It is suggested that even though L. sordidus is a damaging, specific agent, its limited impact on inundated plant populations in South Africa does not justify the inherent risk associated with the release of a biological control agent.
- Full Text: false
- Date Issued: 2018
The Etendeka Igneous Province: magma types and their stratigraphic distribution with implications for the evolution of the Paraná-Etendeka flood basalt province
- Authors: Marsh, Julian S , Ewart, A , Milner, Simon C , Duncan, Andrew R , Miller, R McG
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149762 , vital:38882 , https://doi.org/10.1007/s004450000115
- Description: Detailed geochemical and field data for the volcanic sequence and intrusions of the Etendeka Igneous Province are used to construct a stratigraphic framework for petrogenetic interpretation of the evolution of the Etendeka-Paraná continental flood volcanic event. Geochemical and petrographic characterization of over 1,000 analyzed samples allows 8 mafic and 17 silicic magma types to be recognized.
- Full Text: false
- Date Issued: 2017
The geochemical structure of the Insizwa lobe of the Mount Ayliff complex with implications for the emplacement and evolution of the complex and its Ni-sulphide potential
- Authors: Marsh, Julian S , Allen, P , Fenner, N
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150556 , vital:38984 , https://doi.org/10.2113/106.4.409
- Description: Detailed petrographic, modal and geochemical studies on a number of deep boreholes (exceeding 1.2 km in some instances) along the southeastern margin of the Insizwa lobe of the Mount Ayliff Complex reveal the existence of a geochemical stratigraphy in the mafic intrusive rocks.
- Full Text: false
- Date Issued: 2003
Implications of a new 40Ar/ 39Ar age for a basalt flow interbedded with the Etjo Formation, Northeast Namibia
- Authors: Marsh, Julian S , Swart, Roger S , Phillips, D
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150364 , vital:38970 , https://doi.org/10.2113/106.4.281
- Description: A reliable 40Ar/39Ar plateau age of 180 ± 1.2 Ma (1σ) has been obtained for fresh basalt lava interbedded with aeolian Etjo Formation sandstones south-southwest of Grootfontein in northeast Namibia. This indicates that the Early Jurassic Karoo flood basalt sequence extended from Botswana into northeast Namibia at least as far as 18 east and that this may mark the eastern extent of the Early Cretaceous Etendeka Igneous Province.
- Full Text: false
- Date Issued: 2003
Geochemical constraints on coupled assimilation and fractional crystallization involving upper crustal compositions and continental tholeiitic magma
- Authors: Marsh, Julian S
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140432 , vital:37888 , https://doi.org/10.1016/0012-821X(89)90021-6
- Description: The commonly analyzed trace elements in tholeiites can be subdivided into three groups depending on their sense of enrichment or depletion in upper continental crust in relation to fractional crystallization. Lithophile incompatible elements are enriched in crustal rocks and by fractional crystallization, whereas compatible transition elements such as Ni and Cr are depleted. A small third group comprising Ti, V, Fe, and sometimes P, enrich with crystallization but are depleted in the crust.
- Full Text: false
- Date Issued: 2002
Basalt geochemistry and tectonic discrimination within continental flood basalt provinces
- Authors: Marsh, Julian S
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140412 , vital:37886 , https://doi.org/10.1016/0377-0273(87)90035-7
- Description: Continental flood basalts are usually regarded as a single tectonomagmatic entity but frequently quoted examples exhibit a variety of tectonic settings. In one well-studied, classic, flood basalt province, the Mesozoic Karoo province of southern Africa, magmatism occurred in the following tectonic settings: (a) continental rifting leading to ocean-floor spreading in the South Atlantic Ocean (Etendeka suite of Namibia); (b) stretched continental lithosphere and rifting not leading directly to ocean-floor formation (Lebombo suite of southeastern Africa); and (c) an a-tectonic, within-plate, continental setting characterized by an absence of faulting or warping (Lesotho highlands and Karoo dolerites of South Africa).
- Full Text: false
- Date Issued: 2003
Evolution of a strongly differentiated suite of phonolites from the Klinghardt Mountains, Namibia
- Authors: Marsh, Julian S
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140400 , vital:37885 , https://doi.org/10.1016/0024-4937(87)90023-5
- Description: Phonolites of Tertiary age occur as eroded tholoids, lava flows, ignimbrites, and coulees in the Klinghardt Mountains of southern Namibia. Sixty samples have been analyzed for major and trace elements and fourteen of these for 87SR 86SR. The phonolites lie close to the low-pressure cotectics in Q-Ne-Ks, in keeping with their petrography which indicates that most samples have phenocrysts of both nepheline and sanidine. Na has been variably lost from the rocks during crystallization and devitrification/alteration of hypocrystalline specimens.
- Full Text: false
- Date Issued: 2003
REE fractionation and Ce anomalies in weathered Karoo dolerite
- Authors: Marsh, Julian S
- Date: 1991
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145819 , vital:38469 , https://doi.org/10.1016/0009-2541(91)90099-D
- Description: Analyses of samples from a weathering profile on Karoo dolerite allow elements to be divided into three groups depending on their behaviour. Si, K, Na, Mg, Ca, Sr, Ba and V are mobilized and removed from weathered products. Fe, Al. Ti, Zr, Hf, Zn, Cu, Sc, Co and Ni are immobile. REE, Y, and to a lesser extent Cr, are mobile and redistributed within the profile without a net loss of these elements from the profile. Large positive Ce anomalies are developed in oxidized weathered products by preferential leaching of the other REE's. Negative Ce anomalies and REE enrichment is a feature of less altered dolerite.
- Full Text: false
- Date Issued: 1991
Petrogenesis of late Archaean flood-type basic lavas from the Klipriviersberg Group, Ventersdorp Supergroup, South Africa
- Authors: Marsh, Julian S , Bowen, M P , Rogers, N W , Bowen, T B
- Date: 1992
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145829 , vital:38470 , https://doi.org/10.1093/petrology/33.4.817
- Description: The Klipriviersberg Group is a small continental flood-type tholeiitic suite forming the basal unit of the Ventersdorp Supergroup, an undeformed late-Archaean supracrustal sequence covering 200000 km2 in the SW part of the Kaapvaal Craton. From the base up, the Klipriviersberg Group consists of the Westonaria, Alberton, Orkney, Jeannette, Loraine, and Edenville formations, with a maximum combined thickness of 1–8 km. Samples were obtained from several borehole cores in the Klerksdorp goldfield close to the type area of the Klipriviersberg Group.
- Full Text: false
- Date Issued: 1992
Distribution of Ca in highly fractionated peralkaline magmas
- Authors: Marsh, Julian S
- Date: 1976
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/132974 , vital:36914 , https://doi.org/10.1016/0012-821X(76)90106-0
- Description: Many peralkaline rhyolites and granites contain less than 0.15 wt.% CaO. In contrast, strongly fractionated peralkaline nepheline syenites and phonolites usually contain greater than 0.5 wt.% CaO. Consideration of known distributions of Ca between crystals and liquid in conjunction with crystal fractionation does not provide an adequate explanation of the contrasting levels of Ca depletion observed. Examination of the suites of late-crystallizing accessory phases in peralkaline rocks suggests that Ca is more soluble in undersaturated magmas than in over-saturated magmas. Activities for CaO in silicic and phonolitic rocks are calculated and the latter have higher CaO activities than the former and this may manifest itself in the different suites of accessory phases and levels of Ca depletion noted in natural rocks.
- Full Text: false
- Date Issued: 1976
Volcanic rocks of the Witwatersrand Triad, South Africa. II: petrogenesis of mafic and felsic rocks of the Dominion Group
- Authors: Marsh, Julian S , Bowen, Michael P , Rogers, N W , Bowen, Teral B
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140443 , vital:37889 , https://doi.org/10.1016/0301-9268(89)90075-2
- Description: A bimodal suite of volcanic rocks builds the bulk of the Dominion Group which, with an age of ∼ 2.72 Ga, is the oldest cover sequence overlying the granite-greenstone Archaean basement of the Kaapvaal craton in the western Transvaal, South Africa. The basic lavas are relatively rich in SiO2 (50–58%) and aphyric and exhibit a large compositional range. This variation is typically tholeiitic in that it is characterized by strong enrichment of Ti, Fe, and V in differentiated lavas.
- Full Text: false
- Date Issued: 2003
Aenigmatite stability in silica-undersaturated rocks
- Authors: Marsh, Julian S
- Date: 1975
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/132942 , vital:36911 , https://doi.org/10.1007/BF00373333
- Description: Aenigmatite is common in many trachytes, phonolites and agpaitic nepheline syenites. Petrographic evidence suggests that the aenigmatite in these rocks arises by the reaction of Ti-magnetite with a peralkaline silica-undersaturated liquid, and it is postulated that a no-oxide field, where aenigmatite is stable, exists in alkaline undersaturated magmas.
- Full Text: false
- Date Issued: 1975
Regulatory incoherence and economic potential of freshwater recreational fisheries: the trout triangle in South Africa
- Authors: Marire, Juniours , Snowball, Jeanette D , Fraser, Gavin C G
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68621 , vital:29295 , https://www.tandfonline.com/doi/abs/10.2753/JEI0021-3624480406
- Description: Publisher version , We apply John R. Commons’s negotiational psychology, specifically his principle of sovereignty, to the development of a discordant regulatory culture and its likely impact on the economic potential of recreational fishing. Using South African environmental judicial precedents and other documentation, we formulate six plausible hypotheses. We argue that regulatory incoherence, entitlement insecurity, corporate-dominated social valuation, strategic power coalitions, lack of procedural fairness, and the extent of judicial enforcement of environmental rights help explain the economic potential and isolation of the freshwater recreational fisheries sector. We find a consistent pattern of extraction and monopolization of sovereign power by the Department of Mineral Resources from propertied parties. Thus, regulatory domination is a major mechanism affecting the economic potential of recreational fisheries in the Trout Triangle. While Commons postulated that private property is a sufficient condition for participation in the determination and use of sovereign power, we argue that private/public property is only a necessary condition. The conjunctive sufficient condition is the existence of both regulatory coherence between spheres of government and property.
- Full Text: false
- Date Issued: 2014
The inhibitory effects of various substrate pre-treatment by-products and wash liquors on mannanolytic enzymes
- Authors: Malgas, Samkelo , Van Dyk, J Susan , Abboo, Sagaran , Pletschke, Brett I
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66156 , vital:28911 , https://doi.org/10.1016/j.molcatb.2015.11.014
- Description: publisher version , Biomass pre-treatment is essential for achieving high levels of bioconversion through increased accessibility of hydrolytic enzymes to hydrolysable carbohydrates. However, pre-treatment by-products, such as sugar and lignin degradation products, can negatively affect the performance of hydrolytic (mannanolytic) enzymes. In this study, two monomeric sugars, five sugar degradation products, five lignin derivatives and four liquors from biomass feedstocks pre-treated by different technologies, were evaluated for their inhibitory effects on mannanolytic enzymes (α-galactosidases, β-mannanases and β-mannosidases). Lignin derivatives elicited the greatest inhibitory effect on the mannanolytic enzymes, followed by organic acids and furan derivatives derived from sugar degradation. Lignin derivative inhibition appeared to be as a result of protein–phenolic complexation, leading to protein precipitating out of solution. The functional groups on the phenolic lignin derivatives appeared to be directly related to the ability of the phenolic to interfere with enzyme activity, with the phenolic containing the highest hydroxyl group content exhibiting the greatest inhibition. It was also demonstrated that various pre-treatment technologies render different pre-treatment soluble by-products which interact in various ways with the mannanolytic enzymes. The different types of biomass (i.e. different plant species) were also shown to release different by-products that interacted with the mannanolytic enzymes in a diverse manner even when the biomass was pre-treated using the same technology. Enzyme inhibition by pre-treatment by-products can be alleviated through the removal of these compounds prior to enzymatic hydrolysis to maximize enzyme activity.
- Full Text: false
- Date Issued: 2016
The concentrations of the noble metals in Southern African flood-type basalts and MORB: implications for petrogenesis and magmatic sulphide exploration
- Authors: Maier, Wolfgand D , Barnes, Sarah-Jane , Marsh, Julian S
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150573 , vital:38985 , https://doi.org/10.1007/s00410-003-0480-z
- Description: Concentrations of the platinum-group elements have been determined in several suites of southern African flood-type basalts and mid-ocean ridge basalt (MORB), covering some 3 Ga of geologic evolution and including the Etendeka, Karoo, Soutpansberg, Machadodorp, Hekpoort, Ventersdorp and Dominion magmas.
- Full Text: false
- Date Issued: 2003
The distribution of platinum group elements in the Insizwa lobe, Mount Ayliff Complex, South Africa: implications for Ni-Cu-PGE sulfide exploration in the Karoo igneous province
- Authors: Maier, W D , Marsh, Julian S , Barnes, Sarah-Jane , Dodd, D C
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150353 , vital:38969 , https://0-doi.org.wam.seals.ac.za/10.2113/gsecongeo.97.6.1293
- Description: The Mount Ayliff Complex of the Eastern Cape province of South Africa is a layered intrusion of some 800 km2 surface area and up to 1,200 m thickness. On the basis of compositional similarities and spatial association, it is generally interpreted to form part of the Karoo igneous province. Similarities between the Mount Ayliff Complex and the staging chambers and feeder conduits to flood basalts that host magmatic sulfide ores elsewhere in the world suggest that the Mount Ayliff Complex may have an enhanced potential for Noril’sk-Talnakh–type massive Ni-Cu sulfide ores, an idea that is supported by the well-known sulfide occurrence at Waterfall Gorge.
- Full Text: false
- Date Issued: 2002
Unexpected transformations of 3-(bromoacetyl)coumarin provides new evidence for the mechanism of thiol mediated dehalogenation of α-halocarbonyls
- Authors: Magwenzi, Faith N , Khanye, Setshaba D , Veale, Clinton G L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66200 , vital:28916 , https://doi.org/10.1016/j.tetlet.2017.01.082
- Description: publisher version , The mechanism for the thiol mediated dehalogenation of α-halogenated carbonyls has remained an unresolved problem, despite its ongoing application in synthetic organic chemistry. Nakamura and co-workers first proposed that net dehalogenation occurs via sequential nucleophilic substitutions, while Israel and co-workers concluded that the rate at which dehalogenation occurred suggested that dehalogenation proceeds in a single concerted step. In this study, we investigated the debromination and nucleophilic substitution of 3-(bromoacetyl)coumarin with a variety of thiophenols, whose electron donating or withdrawing natures resulted in large variations in the degree of nucleophilic substitution and dehalogenation products, respectively. Results from these experiments, in addition to an unexpected formation of thioether containing dibenzo[b,d]pyran-6-ones from a Robinson annulation, has provided new evidence for this disputed mechanism.
- Full Text: false
- Date Issued: 2017
How does subjective well-being evolve with age? A literature review
- Authors: López Ulloa, Beatriz Fabiola , Moller, Valerie , Sousa-Poza, Alfonso
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67185 , vital:29056 , https://doi.org/10.1007/s12062-013-9085-0
- Description: publisher version , This literature review provides an overview of the theoretical and empirical research in several disciplines on the relation between ageing and subjective well-being, i.e., how subjective well-being evolves across the lifespan. Because of the different methodologies, data sets and samples used, comparison among disciplines and studies is difficult. However, extant studies do show either a U-shaped, inverted U-shaped or linear relation between ageing and subjective well-being.
- Full Text: false
- Date Issued: 2013
New placoderm fishes from the Late Devonian of South Africa
- Authors: Long, John A , Anderson, M Eric , Gess, Robert W , Hiller, Norton
- Date: 1997
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/72763 , vital:30108 , https://doi.org/10.1080/02724634.1997.10010973
- Description: New placoderm fishes are described from a black shale lens in the Famennian Witpoort Formation, near Grahamstown, South Africa. Arthrodires include a new species of Groenlandaspis, G. riniensis sp. nov., a new genus of groenlandaspidid, Africanaspis doryssa gen. et sp. nov., and a new species of the antiarch Bothriolepis, B. africana sp. nov. This is the first record of the ubiquitous genera Bothriolepis and Groenlandaspis from the African continent. The South African placoderm fauna has demonstrable links with the eastern Gondwana faunas in the close affinity of the Bothriolepis africana with B. barred of Antarctica, and the high diversity of groenlandaspid species, especially the presence of a very high crested form having affinities to Tiaraspis.
- Full Text: false
- Date Issued: 1997
Collaborative research in contexts of inequality: the role of social reflexivity
- Authors: Leibowitz, Brenda , Bozalek, Vivienne , Farmer, Jean , Garraway, James , Herman, Nicoline , Jawitz, Jeff , McMillan, Wendy , Mistri, Gita , Ndebele, Clever , Nkonki, Vuyisile , Quinn, Lynn , Van Schalkwyk, Susan , Vorster, Jo-Anne , Winberg, Chris
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66634 , vital:28973 , https://doi.org/10.1007/s10734-016-0029-5
- Description: publisher version , This article reports on the role and value of social reflexivity in collaborative research in contexts of extreme inequality. Social reflexivity mediates the enablements and constraints generated by the internal and external contextual conditions impinging on the research collaboration. It fosters the ability of participants in a collaborative project to align their interests and collectively extend their agency towards a common purpose. It influences the productivity and quality of learning outcomes of the research collaboration. The article is written by fourteen members of a larger research team, which comprised 18 individuals working within the academic development environment in eight South African universities. The overarching research project investigated the participation of academics in professional development activities, and how contextual, i.e. structural and cultural, and agential conditions, influence this participation. For this sub-study on the experience of the collaboration by fourteen of the researchers, we wrote reflective pieces on our own experience of participating in the project towards the end of the third year of its duration. We discuss the structural and cultural conditions external to and internal to the project, and how the social reflexivity of the participants mediated these conditions. We conclude with the observation that policy injunctions and support from funding agencies for collaborative research, as well as support from participants’ home institutions are necessary for the flourishing of collaborative research, but that the commitment by individual participants to participate, learn and share, is also necessary.
- Full Text: false
- Date Issued: 2017