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South Africa

Private Bag X1

South Africa
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Van Niekerk G.,Private Bag X1 | Loos B.,Private Bag X1 | Nell T.,Private Bag X1 | Engelbrecht A.-M.,Private Bag X1
Future Oncology | Year: 2016

Immunologists have recently taken note of the fact that a host not only resists infection, but also exhibits a capacity to manage the pathology associated with such infection - a concept referred to as tolerance. Here we explore how the tolerance/resistance (T/R) framework can be implemented within an oncological context and explore a number of implications. In particular, the T/R framework distinguishes between pathology manifesting from extensive tumor burden, versus cancers intrinsically expressing a more pathogenic phenotype. Consequently, the T/R framework provides novel methodology in studying the nature of cancer pathology and for marker identification. Additionally, this framework may aid in redefining the therapeutic end point under suitable circumstances: establishing cancer as a chronic, manageable disease. © 2016 Future Medicine Ltd.

Schoeman S.J.,University of Pretoria | Cloete S.W.P.,Private Bag X1 | Cloete S.W.P.,Institute for Animal Production | Olivier J.J.,Private Bag X1 | Olivier J.J.,ARC Animal Production Institute
Livestock Science | Year: 2010

The small stock industry in South Africa is of crucial importance as 80% of the agricultural land is unsuitable for intensive agricultural production. The contribution of 19 resource sheep flocks and goat herds towards breeding objective formulation, genetic improvement and parameter estimation was summarized. Substantial genetic gains resulting from selection for a range of economically important traits were demonstrated, lending impetus to the development and extension of the National Small Stock Improvement Scheme (NSIS). Responses in monetary values in the respective participating small stock breeds ranged from R0.098 for the Dormer to R0.818 for the S.A. Mutton Merino per small stock unit per annum for animals born in the interval from 2000 to 2006. This response is well below what was attained in the resource flocks and in the best participating flocks and herds. Even with this less than optimal change on a national basis, the impact on the sectoral economy is substantial. When related to the cost associated with the NSIS, this improvement is highly cost-effective. The impact of research and development in the small stock industry is therefore substantial, and the small stock industry is foreseen to continue playing an integral role in the national economy. © 2010 Elsevier B.V. All rights reserved.

Blackie M.A.L.,Private Bag X1
Chemistry Education Research and Practice | Year: 2014

This is a conceptual paper aimed at chemistry educators. The purpose of this paper is to illustrate the use of the semantic code of Legitimation Code Theory in chemistry teaching. Chemistry is an abstract subject which many students struggle to grasp. Legitimation Code Theory provides a way of separating out abstraction from complexity both of which provide substantial challenges to students. These are termed semantic gravity (degree of abstraction) and semantic density (degree of complexity). These ideas are then illustrated using chemical examples in order to demonstrate how they may aid the teaching of chemistry. There is a second pedagogical device which Maton, the developer of Legitimation Code Theory, calls 'semantic waves'. This is also discussed in the context of chemistry education. The semantic code could be applied to chemistry at all levels.

Commercial fig production is relatively new to the Mediterranean-type climate Western Cape Province of South Africa. A lack of lateral branch development impedes tree structure development and therefore adequate yields of quality fruit. The chemical rest breaking agents, Lift® (thidiazuron 3gL-1) at 6%, Dormex® (hydrogen cyanamide, 520gL-1) at 4%, mineral oil at 4% and a combination of mineral oil and Dormex® at 2% each were evaluated in a split plot design in combination with tip-pruning vs. no-pruning to overcome apical dominance and increase complexity (Experiment 1). During the 2008/2009 season, an additional investigation was conducted to evaluate the use of thidiazuron and hydrogen cyanamide for harvest scheduling (Experiment 2). Dormex® at 3% and Lift® at 6%, were applied to dormant trees on 30 June 2008, 3 August 2008, 15 August 2008 or 30 August 2008. In general, Lift® can be used to increase the number of buds breaking in 'Bourjasotte Noire' and 'Col de Damme Noire', while tip pruning decreased bud break with a resultant increase in shoot length. Dormex® and oil combined decreased bud break in these two cultivars but was effective on 'Noire de Caromb'. Where bud break was increased the resultant N+1 shoot length was decreased. RBAs increased the number of fruit in both the breba and main crop of 'Noire de Caromb', but decreased fruit size of the breba crop. Our data are not conclusive as to what the reason for low lateral bud break might be but leans towards strong AD in seasons with 400 Utah CU or more, but might include some delayed foliation response in seasons with less than 200 Utah CH. © 2011 Elsevier B.V.

du Toit W.J.,Private Bag X1 | Visagie M.,Private Bag X1
South African Journal of Enology and Viticulture | Year: 2012

Phenolic compounds in red grapes might give an indication of phenolic and colour compositions of the resulting wine. This work compared the Glories, Iland and Bovine Serum Albumin (BSA) tannin precipitation methods for phenolic characterization of South African Pinotage, Merlot, Shiraz and Cabernet Sauvignon red grape samples (n=31). Significant positive correlations were found for certain phenolic characteristics in the grapes measured by these methods. Levels of phenolic compounds in the grapes and correlating wines were in line with literature. Merlot samples often associated more with higher concentrations of seed tannins, which were also reflected in the wines. Significant correlations were also found with the colour characteristics of the resulting wines and some anthocyanin related measurements in the grapes with the Glories and Iland methods, with the latter correlating slightly better. Significant positive correlations were also found between grape and wine tannins as measured with the BSA method. However, malolactic fermentation changed some of these correlations and this needs to be investigated further. This work might give wine producers as well as wine analyses laboratories valuable information regarding the suitability of these methods to characterize the phenolic composition of South African red grapes and their resulting wines.

Burger C.,Private Bag X1 | Van Den Heever D.J.,Private Bag X1
Biomedical Signal Processing and Control | Year: 2015

Eye activity has larger electrical potential than the average electroencephalogram (EEG) recording, thusmaking it one of the major sources of artefacts. Ocular artefacts (OA) must be removed as completelyas possible with little or no loss of EEG to obtain a higher quality EEG. Using independent componentanalysis (ICA), the EEG is separated into independent components (IC) and the contaminated componentis removed, thus removing the OA. However, ICA does not separate the sources completely and some ofthe meaningful EEG is lost. In this paper, a new method combining ICA and wavelet neural networking(WNN) is proposed. In this method, WNN is applied to the contaminated ICs, correcting the OA and thuslowering the data lost. The method was evaluated using simulated and real datasets and the results showthat the OA are successfully removed with very little data loss. © 2014 The Authors. Published by Elsevier Ltd.

Amankwah A.,University of Ghana | Aldrich C.,Private Bag X1 | Aldrich C.,Khan Research Laboratories
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2015

This paper presents a new band selection method for the visualization of hyperspectral images. The method selects three relevant spectral bands to build the red-green-blue composite. The proposed method uses not only mutual information, but also spatial information to select the bands. Results from the proposed method are presented and compared to other state-of-the-art methods in terms of informative content, gradient magnitude and variance. The results show that the proposed method compares favourably with alternative approaches. © 2015 IEEE.

Dillen J.,Private Bag X1
Journal of Computational Chemistry | Year: 2015

The topology of the Ehrenfest force density was studied with Slater-type orbitals (STO). At larger distances from the nuclei, STOs generate similar artefacts as noticed before with Gaussian-type orbitals. The topology of the Ehrenfest force density was found to be mainly homeomorphic with the topology of the electron density. For the first time, reliable integrations of several properties over force density atomic basins were performed successfully. Integration of the electron density of a number of hydrides, fluorides, and chlorides of first row elements over force density basins indicate substantial differences between the partial charges of the atoms as compared with those obtained from electron density basins. Calculations on saturated hydrocarbons confirm that the electronegativity of carbon atoms increases with increasing geometrical strain. Atomic interaction lines are observed to exist in the Ehrenfest force density between the hydrogen atoms of several so-called "congested" molecules, and also in some inclusion complexes of alkanes with helium. However, interaction lines are lacking in several other controversial cases. © 2015 Wiley Periodicals, Inc.

Gaertner M.,Stellenbosch University | Nottebrock H.,University of Potsdam | Fourie H.,Private Bag X1 | Privett S.D.J.,Fynbos Ecoscapes | Richardson D.M.,Stellenbosch University
Perspectives in Plant Ecology, Evolution and Systematics | Year: 2012

Restoration is gaining importance in the management of plant invasions. As the success of restoration projects is frequently determined by factors other than ecological ones, we explored the ecological and financial feasibility of active restoration on three different invaded sites in South Africas Cape Floristic Region. The aim of our study was to identify cost-effective ways of restoring functional native ecosystems following invasion by alien plants. Over three years we evaluated different restoration approaches using field trials and experimental manipulations (i.e. mechanical clearing, burning, different soil restoration techniques and sowing of native species) to reduce elevated soil nutrient levels and to re-establish native fynbos communities. Furthermore we investigated the possibility of introducing native fynbos species that can be used for sustainable harvesting to create an incentive for restoration on private land.Diversity and evenness of native plant species increased significantly after restoration at all three sites, whereas cover of alien plants decreased significantly, confirming that active restoration was successful. However, sowing of native fynbos species had no significant effect on native cover, species richness, diversity or evenness in the Acacia thicket and Kikuyu field, implying that the ecosystem was sufficiently resilient to allow autogenic recovery following clearing and burning of the invasive species. Soil restoration treatments resulted in an increase of available nitrogen in the Acacia thicket, but had no significant effects in the Eucalyptus plantation. However, despite elevated available soil nitrogen levels, native species germinated irrespective whether sown or unsown (i.e. regeneration from the soil seed bank).Without active introduction of native species, native grasses, forbs and other shrubs would have dominated, and proteoids and ericoids (the major fynbos growth forms) would have been under-represented.The financial analysis shows that income from flower harvesting following active restoration consistently outweighs income following passive restoration, but that the associated increase in income does not always justify the higher costs. We conclude that active restoration can be effective and financially feasible when compared to passive restoration, depending on the density of invasion. Active restoration of densely invaded sites may therefore only be justifiable if the target area is in a region of high conservation priority. © 2012 Perspectives in Plant Ecology, Evolution and Systematics.

Van Niekerk G.,Private Bag X1 | Isaacs A.W.,Private Bag X1 | Nell T.,Private Bag X1 | Engelbrecht A.-M.,Private Bag X1
Mediators of Inflammation | Year: 2016

During an infection, expansion of immune cells, assembly of antibodies, and the induction of a febrile response collectively place continual metabolic strain on the host. These considerations also provide a rationale for nutritional support in critically ill patients. Yet, results from clinical and preclinical studies indicate that aggressive nutritional support does not always benefit patients and may occasionally be detrimental. Moreover, both vertebrates and invertebrates exhibit a decrease in appetite during an infection, indicating that such sickness-associated anorexia (SAA) is evolutionarily conserved. It also suggests that SAA performs a vital function during an infection. We review evidence signifying that SAA may present a mechanism by which autophagic flux is upregulated systemically. A decrease in serum amino acids during an infection promotes autophagy not only in immune cells, but also in nonimmune cells. Similarly, bile acids reabsorbed postprandially inhibit hepatic autophagy by binding to farnesoid X receptors, indicating that SAA may be an attempt to conserve autophagy. In addition, augmented autophagic responses may play a critical role in clearing pathogens (xenophagy), in the presentation of epitopes in nonprovisional antigen presenting cells and the removal of damaged proteins and organelles. Collectively, these observations suggest that some patients might benefit from permissive underfeeding. © 2016 Gustav van Niekerk et al.

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