Activated carbon from lignocellulosic waste residues: effect of activating agent on porosity characteristics and use as adsorbents for organic species
- Authors: Olorundare, O F , Okonkwo, J O , Msagati, T A M , Mamba, Bhekie B , Krause, Rui W M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125233 , vital:35748 , https://doi.org/10.1007/s11270-014-1876-2
- Description: This paper reports on the effect of activating agents such as the impregnation ratio of phosphoric acid (1:1–1:5) at constant activation temperature on the performance of porous activated carbon from waste residues (maize tassel). The variation in the impregnation ratio of the produced activated carbon (AC) from 1:1 to 1:5 enabled the preparation of a high surface area (1,263 m2/g) and a large pore volume (1.592 cm3/g) of AC produced from maize tassel (MT) using a convectional chemical activating agent (phosphoric acid). Impregnation ratios (IR) of the precursors were varied between 1:1 and 1:5 in which it was found that the ratio of 1:4 was optimal based on the high surface area, while 1:5 has the optimal pore volume value for the produced activated carbon.
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- Date Issued: 2014
Cytotoxicity, phytochemical analysis and antioxidant activity of crude extracts from Rhizomes of Elephantorrhiza Elephantina and Pentanisia Prunelloides
- Authors: Mpofu, Smart J , Msagati, Titus A M , Krause, Rui W M
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125097 , vital:35728 , https://doi.org/10.4314/ajtcam.v11i1.6
- Description: Background: Elephantorrhiza elephantina (Ee) and Pentanisia prunelloides (Pp) are two medicinal plants which are widely used to remedy various ailments including diarrhoea, dysentery, inflammation, fever, rheumatism, heartburn, tuberculosis, haemorrhoids, skin diseases, perforated peptic ulcers and sore joints in southern Africa (South Africa, Swaziland, Botswana and Zimbabwe). The following study was conducted to explore the in vitro cytotoxicity, antioxidant properties and phytochemical profile of the two medicinal plants. Materials and Methods: The cytotoxicity of the aqueous and methanol extracts and fractions of both species was studied using the brine shrimp lethality tests (BST) for the first time. Results: The results demonstrated that the lethality (LC50) for crude extracts for both plants ranged between 1.8 and 5.8 ppm and was relatively greater than that for the methanol, ethyl acetate and chloroform fractions of the extracts which ranged between 2.1 ppm and 27 ppm. This suggested that crude extracts were more potent than their respective fractions, further explaining that the different fractions of phytochemicals in these plant species work jointly (in synergy) to exert their therapeutic efficacy. Both aqueous and methanol extracts of the two medicinal plants demonstrated a high degree of antioxidant capacity against the DPPH radical with the Duh and Yen inhibition percentage ranging between 4.5% and 72%. Phytochemical studies of the rhizome extracts showed that the major compounds present include flavonoids, tannins, anthocyanidins, anthraquinones, triterpenoids (oleanolic acid), the steroidal saponin Diosgenin, the sugars, rhamnose, glucuronic acid, Arabinose and hexoses. Conclusion: This is the first report of the detection and isolation of diosgenin and oleanolic acid from the rhizome extracts of Ee and Pp. All structures were determined using spectroscopic/spectrometric techniques (1H NMR and 13C and LC-ESI-MS) and by comparison with literature data.
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- Date Issued: 2014
Potential Gaps during the Transition from the Embodied through Symbolic to Formal Worlds of Reflective Symmetry:
- Authors: Mhlolo, Michael K , Schäfer, Marc
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141117 , vital:37945 , https://doi.org/10.1080/10288457.2014.925269
- Description: Even though reflective symmetry is heavily embedded in the everyday, learners continue to experience challenges when they mathematize concepts from this informal/everyday context. In this article we argue that symmetry exists in nature, it can also be symbolized algebraically and it can be abstracted into the world of axioms and theorems. We problematize this multiple nature of symmetry which on one hand is supportive and on the other acts as a contributory factor to learners' gaps in knowledge. Tall's three worlds of mathematics helped us to show the transition of symmetry from the embodied through symbolic to the formal world and the inherent gaps attributed to the shifts in thinking thereof. We then used this same framework to analyse learners' responses to a reflective symmetry task. The results show that many learner responses could be explained explicitly by the lack of flexibility in the applicability of experiences in the embodied world of reflective symmetry.
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- Date Issued: 2014
Re-thinking engagement: Dialogic strategies of alignment in letters to two South African newspapers
- Authors: Smith, Jade , Adendorff, Ralph
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125876 , vital:35828 , https://doi.org/10.1080/10228195.2014.909872
- Description: This article uses an appraisal analysis of 40 letters to the Daily Sun and The Times newspapers in South Africa to illustrate a reconceptualisation of the Engagement system. It discusses dialogism (Bakhtin 1981), which inspired the creation of the Engagement framework by White (2003), who classified attempts to either align or disalign readers with a writer’s stance. Contrary to the options for dialogic Engagement proposed by Martin and White (2005) and White and Don (2012), the data suggests that not all Engagement strategies carry equal power of alignment, as the framework’s systemic layout implies. This prompts a re-thinking of the Engagement categories as occurring along a continuum of their strength.
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- Date Issued: 2014
Reclaiming syndicalism: from Spain to South Africa to Global Labour Today
- Authors: van der Walt, Lucien
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144824 , vital:38382 , DOI: 10.15173/glj.v5i2.1153
- Description: Union politics remain central to the new century. It remains central because of the ongoing importance of unions as mass movements, internationally, and because unions, like other popular movements, are confronted with the very real challenge of articulating an alternative, transformative vision. There is much to be learned from the historic and current tradition of anarcho-and revolutionary syndicalism.
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- Date Issued: 2014
Stable isotope ratios indicate differential omnivory among syntopic rocky shore suspension-feeders
- Authors: Richoux, Nicole B , Vermeulen, Ilke , Froneman, P William
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68261 , vital:29224 , https://doi.org/10.1007/s00227-013-2358-6
- Description: Publisher version , We utilised stable isotope ratios to assess differences in diet among three indigenous and syntopic rocky shore suspension-feeders (mussels Perna perna, barnacles Tetraclita serrata, and polychaetes Gunnarea gaimardi). We also determined the spatial and temporal variability in the suspension-feeder diets by collecting specimens on two occasions from two regions adjacent to hydrologically distinct river mouths (i.e. one with larger annual freshwater throughput than the other). The results showed that the isotopic niches (used as proxies for trophic niches) of the three species did not overlap and that the barnacles occupied a trophic position (3.4) well above those of the mussels (2) and polychaetes (2.6). We ascribed the interspecific differences primarily to the disparate feeding mechanisms used by the species. Large-scale regional (~50 km) differences in suspension-feeder diets were apparent, but not small-scale (up to a few km north and south of each estuary mouth). The regional differences in diet resulted from the increased availability of estuarine-origin suspended particulate matter (SPM) and zooplankton in the region adjacent to the river with relatively larger freshwater output, although overall incorporation of zooplankton versus mixed SPM into consumer diets was relatively consistent between regions and through time. Temporal shifts in suspension-feeder diets were apparent from stable carbon isotope ratios in the consumers. Our results showcase the measurable effects of regional-scale processes that can alter the food sources for dominant primary consumers in the rocky intertidal, thus potentially affecting entire food webs through bottom-up processes. The clear evidence for trophic niche partitioning offers valuable insights into how potentially strong competitors can coexist.
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- Date Issued: 2014
Starways Arts: a built environment expressing holistic lifestyles dedicated to visual and performing arts in Hogsback, Eastern Cape, South Africa
- Authors: Steele, John
- Date: 2014
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/11260/990 , vital:30179
- Description: In 1992, Anton van der Merwe and his life partner Gwyneth Lloyd moved from Randjesfontein Pottery in Midrand, between Johannesburg and Pretoria, to an undeveloped smallholding in the densely forested rural village of Hogsback. The past 22 years have seen an ongoing process of settling down and construction of necessary buildings. This paper seeks to explore aspects of philosophical and architectural influences that served as some of the foundation stones for creation of an eclectic series of buildings, including their home, visual arts studios, a gallery, a community theatre and guest accommodation. A review of these buildings will show that Van der Merwe and Lloyd have developed an idiosyncratic construction style that incorporates alternative technology with empathetic use of natural resources, which results in organically flowing living and working spaces that are fit for purpose, have substantial presence and have minimal environmental impact.
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- Date Issued: 2014
Human harvesting impacts on managed areas: ecological effects of socially-compatible shellfish reserves
- Authors: Aswani, Shankar , Flores, Carola F , Broitman, Bernardo R
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124664 , vital:35644 , https://doi.10.1007/s11160-014-9376-4
- Description: We examined how human harvesting impacts on managed areas affect the abundance and size distribution of the edible mangrove shellfish Anadara granosa and Polymesoda spp. in the Roviana Lagoon, Solomon Islands. We tested two hypotheses: (1) in areas permanently and temporally closed to human exploitation, abundance and size distribution of these shellfish species is significantly greater than in sites open to exploitation and (2) moderate human disturbance of shell beds, particularly of Polymesoda spp., increases their abundance. Firstly, we studied perceptions of environmental states and processes coupled to foraging and management interventions to assess sociocultural influences on harvesting practices and ascertain the types of management regime that people would consider in a context where poaching and interloping are common practices. Secondly, we compared shellfish abundance and shell size from areas that were permanently protected, temporally reserved for communal harvest, and permanently open for exploitation. Thirdly, drawing from women’s local knowledge, we measured the abundance of Polymesoda spp. in relation to mud compactness in quadrats across the three management regimes. Results showed that both species were significantly more abundant in permanent and temporally closed sites than in open sites. In the mud compactness study, however, while shell abundance was greater in moderately compacted quadrats, there was no statistical relationship between mud compactness and shell abundance within or across the three management regimes. Results suggest that even under the strong impacts of poaching, temporally closed areas have more clams than open areas and are as effective as areas that are permanently closed nominally. The results also suggest that human harvesting regimes can influence the effectiveness of local management decisions and thus are important when designing community-based conservation programs in the Solomon Islands and other Pacific Islands.
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- Date Issued: 2015