A quantitative post-release evaluation of biological control of water lettuce, Pistia stratiotes L. (Araceae) by the weevil Neohydronomus affinis Hustache (Coleoptera: Curculionidae) at Cape Recife Nature Reserve, Eastern Cape Province, South Africa
- Authors: Moore, Gareth R , Hill, Martin P
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6839 , http://hdl.handle.net/10962/d1010987 , http://dx.doi.org/10.4001/003.020.0217 , https://orcid.org/0000-0003-0579-5298
- Description: [from the introduction] Water lettuce, Pistia stratiotes L. (Araceae) is recognized as being among the world’s worst aquatic weeds. In its adventive range, the plant forms extensive mats capable of blocking navigation channels, impeding water flow in irrigation and flood control canals, and disrupting hydropower generation (Holm et al. 1977). Dense mats of the weed prevent light penetration into the water column which negatively affects submerged aquatic plant communities, causing a lowering of the oxygen concentration and thereby reducing benthic invertebrate and fish populations (Neuenschwander et al. 2009).
- Full Text:
- Date Issued: 2012
Anatomy of a pottery bonfiring in the Port St Johns region, Eastern Cape, South Africa
- Authors: Steele, John
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/11260/1034 , vital:30232
- Description: This paper seeks to document and contextualise the unique bonfiring methods of octogenarian potter Alice Gqa Nongebeza, who works from her homestead at Nkonxeni village in the Tombo area near Port St Johns. Her firing technique is compared with those of fellow local potters Debora Nomathamsanqa Ntloya and Nontwazana Dunjana. These three Mpondo potters, and their understudies, create ceramic utilityware and other items for a mainly local market that sometimes also appeals to collectors and tourists. Although they are aware of each other, they use their own clay sources and clayworking methods, and have evolved very different firing techniques. This paper, with reference also to potters in KwaZulu-Natal, shows that Nongebeza, in particular, has developed a rare approach to firing, and calls for the inclusion of her type of firing technique in African firing lexicons. It also calls for greater attention to sequential firing detail as practised by individual potters, in forthcoming reports that add to knowledge about zeroelectricity- usage ceramics production in southern Africa, and elsewhere.
- Full Text:
- Date Issued: 2012
Cooperative wasp-killing by mixed-species colonies of honeybees, Apis cerana and Apis mellifera
- Authors: Tan, K , Yang, M-Y , Li, H , Zhang, Z-L , Radloff, Sarah E , Hepburn, H Randall
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6838 , http://hdl.handle.net/10962/d1010979 , http://dx.doi.org/10.1007/s13592-011-0098-5
- Description: The cooperative defensive behaviour of mixed-species colonies of honeybees, Apis cerana and Apis mellifera, were tested against a predatory wasp, Vespa velutina. When vespine wasps hawk honeybees at their nest entrances, the difference in the numbers of bees involved in heat-balling among pure species and mixed-species colonies was not significantly different. However, in the mixed colonies, the numbers of A. cerana and A. mellifera workers involved in heat-balling were significantly different. The duration of heat-balling among these three groups was significantly different. During heat-balling, guard bees of both species in mixed colonies raised their thoracic temperatures and the core temperatures of the heat-balls were about 45°C, which is not significantly different from that of the pure species. These results suggest that the two species of honeybees can cooperate in joint heat-balling against the wasps, but A. cerana was more assertive in such defence.
- Full Text: false
- Date Issued: 2012
Cryptic variation in an ecological indicator organism: mitochondrial and nuclear DNA sequence data confirm distinct lineages of Baetis harrisoni Barnard (Ephemeroptera: Baetidae) in southern Africa
- Authors: Pereira-da-Conceicoa, L L , Price, Benjamin W , Barber-James, Helen M
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:7151 , http://hdl.handle.net/10962/d1011855
- Description: Baetis harrisoni Barnard is a mayfly frequently encountered in river studies across Africa, but the external morphological features used for identifying nymphs have been observed to vary subtly between different geographic locations. It has been associated with a wide range of ecological conditions, including pH extremes of pH 2.9–10.0 in polluted waters. We present a molecular study of the genetic variation within B. harrisoni across 21 rivers in its distribution range in southern Africa.
- Full Text:
- Date Issued: 2012
Evaluation of a service-learning elective as an approach to enhancing the pharmacist's role in health promotion in South Africa
- Authors: Srinivas, Sunitha C , Wrench, Wendy W
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6443 , http://hdl.handle.net/10962/d1006630
- Description: Background. A service-learning (SL) elective offered to final-year pharmacy students was introduced in 2007. The elective demonstrated a holistic approach to creating opportunities for future pharmacists to understand the current needs and future challenges of the burden of disease in developing countries such as South Africa and to foresee their key roles in health promotion. Methods. The 2007 Sasol National Festival of Science and Technology (SciFest) was chosen as the ideal platform to implement this elective. Evaluation of the elective was carried out in association with the Academic Development Centre using a web-based software tool known as the ADC evaluation assistant (ADCEA). The ADCEA consisted of a ‘question bank’ from which the course facilitators selected nine ranked closed questions as well as two open-ended questions. Results. SciFest participation, in the course of the service-learning elective, was acknowledged by students to have prepared them as responsible citizens to undertake health promotion in the public sector healthcare system. Conclusion. Students’ experiences of the learning opportunities provided in the SciFest elective highlight the strengths of this SL programme.
- Full Text:
- Date Issued: 2012
Graviton n-point functions for UV-complete theories in Anti-de Sitter space
- Authors: Brustein, R , Medved, A J M
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6820 , http://hdl.handle.net/10962/d1004427
- Description: We calculate graviton n-point functions in an anti-de Sitter black brane background for effective gravity theories whose linearized equations of motion have at most two time derivatives. We compare the n-point functions in Einstein gravity to those in theories whose leading correction is quadratic in the Riemann tensor. The comparison is made for any number of gravitons and for all physical graviton modes in a kinematic region for which the leading correction can significantly modify the Einstein result. We find that the n-point functions of Einstein gravity depend on at most a single angle, whereas those of the corrected theories may depend on two angles. For the four-point functions, Einstein gravity exhibits linear dependence on the Mandelstam variable s versus a quadratic dependence on s for the corrected theory.
- Full Text:
- Date Issued: 2012
In vitro dissolution kinetics of Captopril from microspheres manufactured by solvent evaporation
- Authors: Khamanga, Sandile M , Walker, Roderick B
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6390 , http://hdl.handle.net/10962/d1006311
- Description: The aim of this study was to develop and assess captopril-loaded microspheres in which Methocel and Eudragit RS were used as release-controlling factors and to evaluate captopril (CPT) release using kinetic models. Drug-excipient interactions were evaluated using infrared studies, and the physical appearance was characterized using scanning electron microscopy (SEM). A burst effect was observed during the first stage of dissolution for most batches of microspheres. SEM results reveal that this may be attributed to dissolution of captopril crystals that were present on the surface, embedded in the superficial layer of the matrix materials, trapped near the surface of the microspheres, or that may have diffused rapidly through the porous surface of the capsules. The release data generated during in vitro release studies were fitted to zero-order, first-order, Higuchi, Korsmeyer–Peppas, Kopcha, and Makoid–Banakar models. The release kinetics of captopril from most formulations followed a classical Fickian diffusion mechanism. SEM photographs showed that diffusion took place through pores located in the surface of the microcapsules. The Kopcha model diffusion and erosion terms showed a predominance of diffusion relative to swelling or erosion throughout the entire test period. The drug release mechanism was also confirmed by the Makoid–Banakar and Korsmeyer–Peppas model exponents. This further supports a diffusion–release mechanism for most formulations. The models postulate that the total drug released is a summation of several mechanisms (viz., burst release, relaxation-induced controlled release, and diffusional release). These results also support the potential application of Eudragit/Methocel microspheres as a suitable sustained-release drug delivery system for captopril.
- Full Text:
- Date Issued: 2012
Prediction of water temperature metrics using spatial modelling in the Eastern and Western Cape, South Africa
- Authors: Rivers-Moore, N A , Mantel, S , Dallas, H F
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:7071 , http://hdl.handle.net/10962/d1003947 , http://www.scielo.org.za/scielo.php?pid=S1816-79502012000200002&script=sci_arttext
- Description: Key aspects of a river's temperature regime are described by magnitudes, timing and durations of thermal events, and frequencies of extreme exceedance events. To understand alterations to thermal regimes, it is necessary to describe thermal time series based on these statistics. Classification of sites based on their thermal metrics, and understanding of spatial patterns of these thermal statistics, provides a powerful approach for comparing study sites against reference sites. Water temperature regime dynamics should be viewed regionally, where regional divisions have an inherent underpinning by an understanding of natural thermal variability. The aim of this research was to link key water temperature metrics to readily-mapped environmental surrogates, and to produce spatial images of temperature metrics: 37 temperature metrics were derived for 12 months of sub-daily water temperatures at 90 sites in the Eastern Cape and Western Cape provinces, South Africa. These metrics were correlated with 16 environmental variables. Correlations enabled development of multiple regression models which facilitated mapping of temperature metrics over the study area. This approach has the potential to be applied at a national scale as more thermal time series are collected nationally. It is argued that the appropriateness of management decisions in rivers can be improved by including guidelines for thermal metrics at a regional scale. Such maps could facilitate incorporation of a temperature component into management guidelines for water resources.
- Full Text:
- Date Issued: 2012
The use of response surface methodology to evaluate the impact of level 2 SUPAC–IR changes on the in vitro release of metronidazole and ranitidine from a fixed-dose combination tablet
- Authors: King’ori, Loti D , Walker, Roderick B
- Date: 2012
- Language: English
- Type: text , Article
- Identifier: vital:6391 , http://hdl.handle.net/10962/d1006313
- Description: The purpose of this study was to evaluate the effect of different levels of disintegrant (croscarmellose sodium, CCS), binder (polyvinylprrolidone K30, PVP–K30), and lubricant (magnesium stearate) on the in vitro release of metronidazole (MTZ) and rantidine (RTD) from a solid oral fixed-dose combination tablet. The excipient levels investigated were Level 2 changes in component and composition described in the Scale-Up and Post Approval Changes for Immediate Release (SUPAC–IR) guidance (1). Batches of tablets (1000 units) were manufactured by wet granulation using a Saral high-shear mixer granulator and a Manesty B3B rotary tablet press. Weight uniformity, friability, and disintegration of all tablets were assessed, and all batches complied with compendial specifications. The amount of drug released (Q) at ten minutes was dependent on the levels of CCS in the formulation, and the effect of PVP–K30 and magnesium stearate was dependent on the levels of CCS. Synergistic interactions between independent variables were observed for the Q10 value for RTD, whereas PVP–K30 and magnesium stearate exhibited an antagonistic effect on the Q10 values for MTZ and RTD. The use of response surface methodology facilitated an investigation into the effect of Level 2 component and composition changes, as described in SUPAC–IR, on the in vitro release of MTZ and RTD from a fixed-dose combination (FDC) solid oral dosage form (SODF).
- Full Text:
- Date Issued: 2012
Three tales of Theal: biography, history and ethnography on the Eastern Frontier
- Authors: Naidu, Samantha
- Date: 2012
- Language: English
- Type: Article , text
- Identifier: vital:24529 , http://hdl.handle.net/10962/36216 , https://www.jstor.org/stable/23267873?seq=1#page_scan_tab_contents , https://orcid.org/0000-0001-9456-8657
- Full Text:
- Date Issued: 2012
Western alumnae influencing the world
- Authors: Steyaert, Marcia
- Date: 2012
- Subjects: Nyokong, Tebello
- Language: English
- Type: Article , text
- Identifier: vital:7168 , http://hdl.handle.net/10962/d1006069 , Nyokong, Tebello
- Description: In September 2011, IT News Africa, named two Western alumnae, Uche Eze, HBA'06, and Tebello Nyokong, PhD1987 (Chemistry) in their list of top 10 most influential women in science and technology in Africa. Nyokong is a professor of medicinal chemistry and nanotechnology at Rhodes University and is recognized as one of the top three publishing scientists in South Africa.
- Full Text:
- Date Issued: 2012