The chemical composition of silages produced in a Mediterranean climate

(South African J of Animal Science, 2000, 30, Supplement 1: 91-92

First report of an Anabaena Bory strain containing microcystin-LR in a freshwater body in Africa

In South Africa, little is known about the production of microcystin by the genus Anabaena Bory. In April 2012, during a cyanobacterial bloom event in Theewaterskloof Dam, Western Cape province, the plankton was sampled on 10 occasions. The dominant algae belonged to the genus Anabaena, a family of filamentous cyanobacteria known to produce cyanotoxins such as anatoxin-a, harmful to humans and the aquatic foodweb. The specimens isolated lacked the characteristic akinetes and/or heterocysts associated with this genus. Therefore the 16S rRNA gene was Sanger sequenced and a maximum parsimony tree was constructed, confirming its identity as Anabaena ucrainica (Schkorbatow) M. Watanabe. Enzyme-linked immunosorbent assay (ELISA) confirmed the presence of microcystin-LR in the isolated A. ucrainica field sample, while PCR analysis and sequencing further confirmed the presence of mcy genes in this species. It was speculated from the data that prevailing low water-column temperatures and strong gusty winds may have resulted in the lack of akinete or heterocyst production. The Anabaena strain isolated from Theewaterskloof Dam is the first report of a strain containing microcystin-LR belonging to this genus in a freshwater body in Africa.Council for Scientific and Industrial Research and the National Research Foundation of South Africa.http://www.tandfonline.com/loi/taas20hb2016Paraclinical Science

Treated Acid Mine Drainage and Stream Recovery: Downstream Impacts on Benthic Macroinvertebrate Communities in Relation to Multispecies Toxicity Bioassays

Research ArticleThe success and long term effectiveness of extensive and expensive engineering solutions to restore streams impacted by Acid Mine Drainage (AMD) is rarely tested. Concentrations of pollutants were measured in water along a longitudinal gradient from a stretch of the Tweelopie stream, South Africa, that receives pH-treated acid mine drainage (AMD) from an abandoned gold mine. The biotoxic effects of treated AMD were determined through macroinvertebrate biotic indices (SASS5) and a battery of toxicity bioassays. These included the L. sativa, A. cepa, D. magna toxicity and Ames mutagenicity tests, as well as an in vitro human liver cancer cell line HepG2. Even though the Tweelopie stream was moderately to severely degraded by multiple anthropogenic stressors, the impact of the treated AMD was masked by the improvement in the system downstream after mixing with the domestic wastewater effluent receiving stream, and subsequent further dilution as a result of the karst springs downstream. The general improvement of the system downstream was clearly shown by the decrease in the ecotoxicity and mutagenicity in relation to the in-stream macroinvertebrates. PCA multivariate analysis successfully displayed associations between the different environmental variables and the decrease in toxicity and subsequent ecosystem improvement downstream. This study indicated that environmental management of AMD remediation should consider long term assessment strategies, including multiple factors, to promote biological ecosystem recovery

Multiwavelength Observations of Supersonic Plasma Blob Triggered by Reconnection Generated Velocity Pulse in AR10808

Using multi-wavelength observations of Solar and Heliospheric Observatory (SoHO)/Michelson Doppler Imager (MDI), Transition Region and Coronal Explorer (TRACE) 171 \AA, and H$\alpha$ from Culgoora Solar Observatory at Narrabri, Australia, we present a unique observational signature of a propagating supersonic plasma blob before an M6.2 class solar flare in AR10808 on 9th September 2005. The blob was observed between 05:27 UT to 05:32 UT with almost a constant shape for the first 2-3 minutes, and thereafter it quickly vanished in the corona. The observed lower bound speed of the blob is estimated as $\sim$215 km s$^{-1}$ in its dynamical phase. The evidence of the blob with almost similar shape and velocity concurrent in H$\alpha$ and TRACE 171 \AA\ supports its formation by multi-temperature plasma. The energy release by a recurrent 3-D reconnection process via the separator dome below the magnetic null point, between the emerging flux and pre-existing field lines in the lower solar atmosphere, is found to be the driver of a radial velocity pulse outwards that accelerates this plasma blob in the solar atmosphere. In support of identification of the possible driver of the observed eruption, we solve the two-dimensional ideal magnetohydrodynamic equations numerically to simulate the observed supersonic plasma blob. The numerical modelling closely match the observed velocity, evolution of multi-temperature plasma, and quick vanishing of the blob found in the observations. Under typical coronal conditions, such blobs may also carry an energy flux of 7.0$\times10^{6}$ ergs cm$^{-2}$ s$^{-1}$ to re-balance the coronal losses above active regions.Comment: Solar Physics; 22 Pages; 8 Figure

Development of a rapid and sensitive battery of bioassays for risk assessment of cyanobacterial microcystin-LR in drinking water of rural water treatment plants, South Africa

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Genetic Diversity of Maize (Zea maysL.) Inbreds Developed for Highlands and Mid-Altitudes as Revealed by AFLP Markers

Fifty six maize inbred lines developed for highlands and mid-altitudes of Ethiopia and Zimbabwe were fingerprinted using amplified fragment length polymorphism (AFLP) markers. The objectives were to investigate the genetic relationships among the inbred lines and to cluster them into heterotic groups with a view to generate broad-based breeding populations. Seven prescreened pairs of AFLP primers identified 499 scorable fragments, of which 408 (81.7%) were polymorphic. The genetic diversity (Euclidean distance) varied from 0.35 to 0.71 with an average of 0.58. The UPGMA clustering using average linkage methods distinguished four major groups. The highland inbred lines generally separated from the mid-altitude germplasm. Each of these groupings possessed a number of subclusters mostly related to the pedigree records of the inbred lines. Principal coordinate analysis, also demonstrated considerable genetic divergence between and within the genotypes of the different origins. This groupings based on AFLP markers can be utilized to generate heterotic populations that can serve as source material to develop superior inbred lines revealing good combining ability. Moreover, inbred lines of different heterotic groups can be used to launch crossing activities leading to the development of high yielding maize hybrid and synthetic varieties

A cost-benefit analysis of implementing a 54 MW solar PV plant in a South African platinum mining company: A case study

A reliable and secure supply of energy is a prerequisite for adequate output and economic growth – especially in a platinum mining company. With exponential tariff increases, inadequate power supply leading to power cuts, and a carbon tax introduction, this study compared the costs with benefits by implementing a 54 MW solar photovoltaic (PV) plant. Two scenarios were compared over the same 20-year period in a case study of a South African platinum mining company operating in the platinum belt of Rustenburg. The first scenario was grounded upon the decision to proceed with the conventional manner of sourcing electricity from Eskom, South Africa’s power utility. The second scenario assessed the implementation of a 54 MW solar PV plant. The findings reveal that the company could generate 2 439 753 MWh of clean energy over 20 years with an investment of ZAR 910 857 920, giving a ZAR 563 205 994 (11%) carbon tax saving and a ZAR 5 614 426 335 (10%) reduction in electricity costs. Further, installing the solar PV plant could reinforce the company‘s dedication to protecting the environment and creating job opportunities through the employment of staff to install and maintain the plant

A method for multiple superposition of structures

The study of families of protein structures is important in analysing the results of NMR structure determinations and in investigating mechanisms of molecular evolution at the level of conformation. A method is discussed for finding the transformations that mutually superpose an arbitrary number of structures in the least-squares sense given specified atom-to-atom correspondence