A comparison of anthropogenic and elephant disturbance on Acacia xanthophloea (fever tree) populations in the Lowveld, South Africa
- Authors: Botha, Jenny , Witkowski, Ed T F , Shackleton, Charlie M
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181629 , vital:43753 , xlink:href="https://doi.org/10.4102/koedoe.v45i1.10"
- Description: Acacia xanthophloea (the ‘fever tree’) is a popular medicinal species that is traded widely in South Africa. Although it occurs throughout southern Africa, there is increasing pressure on its riverine and marshy habitats. This study compares the impact of harvesting on an A. xanthophloea population located on private land near Komatipoort, Mpumalanga, with two protected populations situated within the Kruger National Park. The densities of the harvested and protected populations were similar (84±8 trees/ha and 85±20 trees/ha, respectively). There were fluctuations in the quotients between frequencies of trees in successive diameter classes, which is common in savanna where high levels of fire, mega-herbivore and anthropogenic disturbance are experienced. The extent of stem damage (stripping of bark and breakage) by elephants in the protected area was significantly higher than the extent of harvesting on private land, although the degree of damage was relatively low, with only 7 % of the populations having been damaged at rates >26 %. The degree of harvesting on private land was relatively low, with the majority of trees having been harvested at rates of less than 10 % of the stem below 2 m. Despite this, ringbarking had occurred (4 %). The basal diameters and heights were significantly lower in the protected population than in the harvested one, suggesting that over time elephant impact was the more severe disturbance. Acacia xanthophloea exhibited high resilience to disturbance, with all the elephant damaged trees and harvested individuals surviving. However, the mean bark thickness measured in local markets (6.3±1.4 mm) was significantly lower than that measured in either the harvested (12.4±1.0 mm) or the KNP (10.3±0.8 mm) populations. As harvesters tend to select the largest individuals in a population to maximise their financial returns, this could mean that smaller individuals are being harvested, and/or bark is not being given sufficient time to grow back after harvesting. Acacia xanthophloea outside protected areas thus need to be monitored and the management improved, preferably in conjunction with the resource users. In addition, traditional healers, those selling medicinal plants and other members of the community need to continue to be encouraged to cultivate this fast growing species.
- Full Text:
- Date Issued: 2002
A workers handbook on HIV and AIDS
- Authors: COSATU
- Date: 2002
- Subjects: COSATU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/135270 , vital:37253
- Description: AIDS is a trade union issue and must be discussed and placed on the agendas of all union meetings. We have committed ourselves to campaign for HIV prevention, care and treatment with the same determination and energy with which we fight many other working class struggles. COSATU has also committed to work in partnership with other trade unions, government, business and organs of civil society in the fight against the disease.”
- Full Text:
- Date Issued: 2002
An assessment of the efficacy of two lysine microencapsulation techniques to determine the quantitative lysine requirement of the South African abalone, Haliotis midae L
- Authors: Shipton, Thomas A , Britz, Peter J , Walker, Roderick B
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184289 , vital:44197 , xlink:href="https://doi.org/10.1046/j.1365-2095.2002.00204.x"
- Description: The quantification of the essential amino acid requirements of a species is a prerequisite to the formulation of biologically optimized diets. In this study, crystalline L-lysine was used in an attempt to determine the quantitative lysine requirement of juvenile Haliotis midae. Two microencapsulation techniques [gelatine/acacia and cellulose acetate phthalate (CAP)] were used to retard leaching of crystalline L-lysine incorporated into semipurified test diets. An assessment of the efficacy of the encapsulation techniques, revealed that despite effective lysine supplementation, H. midae fed semipurified test diets containing encapsulated crystalline L-lysine failed to promote significant improvements in either growth, feed or protein efficiency (P > 0.05). The failure of the crystalline L-lysine to illicit growth and nutritional responses is discussed.
- Full Text:
- Date Issued: 2002
An investigation into multimedia service creation using sip
- Authors: Hsieh, M , Okuthe, J , Terzoli, Alfredo , Wentworth, Peter N
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427533 , vital:72445 , https://www.researchgate.net/profile/Alfredo-Ter-zoli/publication/267852929_An_investigation_into_multimedia_service_creation_using_SIP/links/5523cb990cf2b351d9c338c9/An-investigation-into-multimedia-service-creation-using-SIP.pdf
- Description: This paper investigates two sip architectures and how services creation works in those two environments. The two architectures are SIPCOMM (www. sipcomm. com) and VOCAL (www. vovida. org). As a concrete example we look at how the voicemail service is implemented in both environments and then at how we could implement an alarm service.
- Full Text:
- Date Issued: 2002
Asthenospheric and lithospheric sources for Mesozoic dolerites from Liberia (Africa): trace element and isotopic evidence
- Authors: Dupuy, C , Marsh, Julian S , Dostal, J , Michard, A , Testa, S
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140422 , vital:37887 , https://doi.org/10.1016/0012-821X(88)90067-2
- Description: Combined elemental, and Sr and Nd isotopic data are presented for Mesozoic dolerite dikes of Liberia (Africa) which are related to the initial stage of opening of the Atlantic Ocean.
- Full Text: false
- Date Issued: 2002
Being Brave: Writing Environmental Education Research
- Authors: Lotz-Sisitka, Heila , Burt, Jane C
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184734 , vital:44267 , xlink:href="https://eric.ed.gov/?id=EJ654591"
- Description: The heroine came back from her very important quest and sat down to write a thesis . . . While mythical journeys do not always end this way, the stories have to be told. The work of telling the story in the hero’s journey is often left untold. This paper explores some of the headwork that goes into textwork (Van Manen, 1995) in environmental education research. We argue that writing is an integral part of the research process, and should not be viewed as an “add on” or a silent, untold part of the adventure. We reflect on some of the institutional and epistemological issues associated with writing social science (in our case environmental education) research texts. Writing research is never an easy enterprise, it is bound by history and tradition, convention, institutional habit, and regulation. It is also constrained by the uncertainty of the process of writing itself, by problems of power relations in research, and the difficulty of writing to represent experience rigorously and authentically while recognizing that all writing is a constructed symbolic representation of experience. The paper reflexively reviews our attempts at “being brave” in the construction of our research texts.
- Full Text:
- Date Issued: 2002
CANS: Customizable Alarm Notification System, an H. 323 Signalling Service
- Authors: Penton, J , Terzoli, Alfredo
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427562 , vital:72447 , https://www.cs.ru.ac.za/research/g97p5142/Docs/CANSSATNAC2002.pdf
- Description: H. 323 is a standardized signalling protocol for Voice over IP (VoIP) networks, which defines the terminal equipment and services that ena-ble real-time multimedia (data, voice, and video) communication over packetbased networks. One of the major advantages of carrying voice over Computer Networks, as opposed to the traditional SCN, is the pos-sibility of creating a wealth of services and integrating them into the network with minimal time and cost. Among these services, exists a subset that may need to interact at the signalling layer and H. 323 (ver-sion 4) provides mechanisms for this. This paper focuses on an appli-cation that was developed to explore and demonstrate H. 323’s signal-ling service creation and extension mechanisms.
- Full Text:
- Date Issued: 2002
Curriculum patterning in environmental education: A review of developments in formal education in South Africa
- Authors: Lotz-Sisitka, Heila
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/437280 , vital:73365 , ISBN 978-07969-2001-0 , https://www.hsrcpress.ac.za/books/environmental-education-ethics-action-in-southern-africa
- Description: Written by environmental practitioners from across the region, the Monograph is a window onto envi-ronmental challenges in a diversity of African con-texts. These contexts include Malawian officials and community leaders, new to multi-level governance, taking up the challenge of environmental manage-ment in villages and districts; Ugandan small-scale farmers in partnership with NGOs trying to produce sustainably for the household and the international market; and government-civil society partnerships in South Africa, where the political transformation of the education system introduced a focus on envi-ronment and human rights in the national school curriculum.
- Full Text:
- Date Issued: 2002
Cyclic voltammetric studies of octabutylthiophthalo-cyaninato-cobalt (II) and its self-assembled monolayer (SAM) on gold electrode
- Authors: Ozoemena, Kenneth , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289567 , vital:56650 , xlink:href="https://doi.org/10.1142/S1088424602000130"
- Description: The synthesis of thiol-derivatized cobalt phthalocyanine complex, 2,3,9,10,16,17,23,24-octa (butylthiophthalocyaninatocobalt(II) (CoOBTPc) is described. Cyclic voltammetric data of this complex in DMF showed five quasi-reversible and reversible, diffusion-controlled redox couples, comprising both the phthalocyanine ring and central metal redox processes. The CoOBTPc complex forms a self-assembled monolayer (SAM) on gold electrode. The investigation of the integrity of this SAM, using the established cyclic voltammetric methods in aqueous alkaline solutions, gave evidence about the formation of a stable and easily reproducible monolayer. However, due to its susceptibility to destruction via oxidative and reductive desorptions, its potential application as an electrochemical sensor in alkaline pH is limited to a potential window of between −0.20 and +0.55 V vs Ag/AgCl.
- Full Text:
- Date Issued: 2002
Effects of axial ligands on the photophysical properties of silicon octaphenoxyphthalocyanine
- Authors: Maree, M David , Nyokong, Tebello , Suhling, Klaus , Phillips, David
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289582 , vital:56651 , xlink:href="https://doi.org/10.1142/S1088424602000452"
- Description: The photochemistry and photophysics of six axially substituted silicon phthalocyanines are reported and show the importance of the axial groups in the photochemistry of these compounds. The fluorescence quantum yields are especially affected by the axial ligand. A very good correlation was found for the experimentally determined fluorescence lifetimes and the theoretically determined lifetimes using the Strickler-Berg equation for the unaggregated molecules.
- Full Text:
- Date Issued: 2002
Employee ownership in the context of globalisation: a developing country perspective
- Authors: NALEDI
- Date: 2002
- Subjects: NALEDI
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/153882 , vital:39532
- Description: This paper represents an initial set of ideas focused on employee ownership within the developing country context. The central question being explored is ‘To what extent can employee ownership support the broader goal of poverty reduction in South Africa (and, by extension, in the developing country context)?’. This is a rather broad question, and as such this note sets out to begin the discussion on this question, rather than seek to provide a definite set of answers. The critical perspectives put forward in this note draw heavily on experiences and debates in South Africa, and particularly those within the labour movement.
- Full Text:
- Date Issued: 2002
Extending the matching facilities of Linda
- Authors: Wells, George C , Chalmer, A B , Clayton, Peter G
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430452 , vital:72692 , https://doi.org/10.1007/3-540-46000-4_34
- Description: This paper discusses the associative matching mechanism used in the Linda coordination language for the retrieval of data. There are a number of problems with this mechanism which are discussed in the light of the requirements of applications using Linda. A number of solutions to these problems have been proposed. These are discussed and compared with a new approach to solving these problems. The benefits and the limitations of the new approach are considered, showing how it provides a considerable improvement in this area.
- Full Text:
- Date Issued: 2002
Fuel wood use in South Africa: Where to in the 21st Century?
- Authors: Williams, Anthony , Shackleton, Charlie M
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183026 , vital:43905 , xlink:href="https://doi.org/10.1080/20702620.2002.10434611"
- Description: South Africa is well known for the dichotomous nature of its economy, with its juxtaposed first and third world characteristics, perhaps nowhere more starkly evident than in the energy sector. South Africa produces and consumes over 60% of the total electrical energy on the African continent, and is ranked twelfth in the world in terms of carbon emissions (EIA, 2002). Yet the majority of the South African population does not have access to electricity, and despite the enormous strides taken since 1994 to increase household access to electricity (NER, 2001), newly electrified households, more often than not, cannot afford the appliances nor the monthly costs required to significantly improve their quality of life (White et al., 1997). Thus, most rural and many peri-urban households continue to use fuelwood as their primary energy source (Griffin et al., 1992; Dyer, 1996; Kotze, 1996; Williams et al., 1996). Fuelwood use presents both opportunities and risks.
- Full Text:
- Date Issued: 2002
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
Geometric approximations towards free specular comic shading
- Authors: Winnemöller, Holger , Bangay, Shaun D
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433453 , vital:72971 , https://doi.org/10.1111/1467-8659.00590
- Description: We extend the standard solution to comic rendering with a comic‐style specular component. To minimise the computational overhead associated with this extension, we introduce two optimising approximations; the perspective correction angle and the vertex face‐orientation measure. Both of these optimisations are generally applicable, but they are especially well suited for applications where a physically correct lighting simulation is not required. Using our optimisations we achieve performances comparable to the standard solution. As our approximations favour large models, we even outperform the standard approach for models consisting of 10,000 triangles or more, which we can render exceeding 40 frames per second, including the specular component.
- Full Text:
- Date Issued: 2002
Growth and fruit production of Sclerocarya birrea in the South African lowveld
- Authors: Shackleton, Charlie M
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/181618 , vital:43752 , xlink:href="https://doi.org/10.1023/A:1020579213024"
- Description: Sclerocarya birrea (A.Rich.) Hochst. subsp. caffra (Sond.) Kokwaro. is a common species throughout the semiarid, deciduous savannas of much of sub-Saharan Africa. It is a favoured species and is frequently maintained in homestead plots and arable fields in an agroforestry situation. Although the abundance and popularity of this species has led to several initiatives to commercialise a number of marula products, the sustainability of the resource base with respect to fruit production has not been considered. This paper reports on a field experiment that monitored growth rates and fruit production of a sample of adult trees from several wild populations. Mean fruit production was 36.8 kg per tree in the first year, and negligible in the second. This was considerably less than previous estimates, which were based largely on small samples or anecdotal reports. The maximum recorded yield was 416.6 kg per tree. Fruit production was positively related to the size of the tree. Growth rates of adult trees were slow. There was a strong positive relationship between mean annual diameter increment and stem diameter. The slow growth rates and low fruit yields indicate that more attention is required regarding the sustainability of there source and its ability to provide sufficient fruit for the growing subsistence and commercial demand at both local and national scales.
- Full Text:
- Date Issued: 2002
Growth patterns of Pterocarpus angolensis in savannas of the South African lowveld
- Authors: Shackleton, Charlie M
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182373 , vital:43824 , xlink:href="https://doi.org/10.1016/S0378-1127(01)00676-4"
- Description: Pterocarpus angolensis D.C. is one of the most valuable indigenous timber species on the African continent south of the equator. Because of its high value, it is actively sought after in a number of countries, and wild populations are diminishing. However, attempts at artificial germination and growth trials have yielded poor results, thus, emphasis needs to be placed on sustainable management of existing populations. Success of in situ management will be enhanced if based on reliable data and knowledge regarding the growth patterns of this species within specific localities and countries. Such comprehensive data are lacking for several countries, including South Africa. This paper presents empirical data on a number of studies investigating the growth patterns of P. angolensis in the central lowveld savannas of South Africa, including phenology, annual diameter increment, size class structure, size of reproductive maturity, and morphometric relationships. The size class profile indicated that there was adequate recruitment of P. angolensis, but with constricted through growth from the suffrutex stage to the sapling stage. A small proportion of individuals attained reproductive maturity at 8 cm diameter, but most were bigger. All stems were reproductively mature by 26 cm diameter. This is below the minimum size for harvesting which is dictated by the need for a well developed heartwood. Annual growth was strongly related to stem size and rainfall during the growing season. Basal area increment of small stems was approximately four times greater than mature stems, and declined with increasing stem size. Over the 6-year-period and across all stem sizes, mean diameter increment was 4.5 mm per year. This rate is towards the lower end of the range of reported growth rates from other countries, and poses particular challenges for the sustainable management of this species in South African savannas.
- Full Text:
- Date Issued: 2002
Indigenous knowledge and the school curriculum: A review of developing methods and methodological perspectives
- Authors: O’Donoghue, Rob B , Neluvhalani, Edgar
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/437292 , vital:73366 , ISBN 978-07969-2001-0 , https://www.hsrcpress.ac.za/books/environmental-education-ethics-action-in-southern-africa
- Description: Written by environmental practitioners from across the region, the Monograph is a window onto envi-ronmental challenges in a diversity of African con-texts. These contexts include Malawian officials and community leaders, new to multi-level governance, taking up the challenge of environmental manage-ment in villages and districts; Ugandan small-scale farmers in partnership with NGOs trying to produce sustainably for the household and the international market; and government-civil society partnerships in South Africa, where the political transformation of the education system introduced a focus on envi-ronment and human rights in the national school curriculum.
- Full Text:
- Date Issued: 2002
Interaction of sulfur dioxide and cyanide with cobalt (II) tetrasulfophthalocyanine in aqueous media
- Authors: Thamae, Mamothibe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289595 , vital:56652 , xlink:href="https://doi.org/10.1016/S0277-5387(01)00968-8"
- Description: Kinetic and equilibrium studies for the coordination of cyanide or sulfur dioxide to the cobalt(II) tetrasulfophthalocyanine ([CoTSPc]4−) complex are reported. The equilibrium constant for the coordination of the cyanide under pH 11 conditions and an oxygen atmosphere, and the formation of [(CN−)2Co(III)TSPc]5− species, was found to be 2.1×101 dm3 mol−1 and the rate constant, kf was found to be 7.4 dm3 mol−1 s−1. Similarly, the coordination of SO2 to [CoTSPc]4− occurred with an equilibrium constant of 8.7×101 dm3 mol−1 and a rate constant of 2.1×102 dm3 mol−1 s−1, at pH 11. These rate and equilibrium constants represent the coordination of the second cyanide or sulfur dioxide ligands to the [CoTSPc]4− species. Coordination of the first ligand occurred faster than that of the second ligand in both cases. The coordination is accompanied by the oxidation of the central Co(II) metal with the formation of a Co(III) tetrasulfophthalocyanine species.
- Full Text:
- Date Issued: 2002
Iron perchlorophthalocyanine and tetrasulfophthalocyanine catalyzed oxidation of cyclohexane using hydrogen peroxide, chloroperoxybenzoic acid and tert-butylhydroperoxide as oxidants
- Authors: Grootboom, Natasha , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289606 , vital:56653 , xlink:href="https://doi.org/10.1016/S1381-1169(01)00404-6"
- Description: Polychlorophthalocyanine (Cl16PcFeII) and tetrasulfophthalocyanine ([FeIITSPc]4−) complexes of iron are employed as catalysts for the oxidation of cyclohexane using tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (m-CPBA) and hydrogen peroxide as oxidants. Catalysis using the Cl16PcFeII was performed in a dimethylformamide:dichloromethane (3:7) solvent mixture. For the [FeIITSPc]4−catalyst, a water:methanol (1:9) mixture was employed. The products of the catalysis are cyclohexanone, cyclohexanol and cyclohexanediol. The relative yields of the products depended on oxidant and the catalyst. TBHP was found to be the best oxidant since minimal destruction of the catalyst and higher selectivity in the products were observed when this oxidant was employed. The mechanism of the oxidation of cyclohexane in the presence of the Cl16PcFeII and [FeIITSPc]4− involves the oxidation of these catalysts, forming an Fe(III) phthalocyanine species as an intermediate. Higher yields were observed when [FeTSPc]4− was employed as a catalyst, which is more soluble than the perchlorinated iron phthalocyanine catalyst.
- Full Text:
- Date Issued: 2002