Die taak en metodes van die musiek-opvoeding aan S.A. Universiteite.

In ’n vorige artikel het ek verskillende aspekte van die Musiekopvoeding in Suid-Afrika oorsigtelik behandel en onder andere verwys na die dringende noodsaaklikheid van ’n sistematiese, gebalanseerde opleiding van ’n nuwe Musiekonderwyserstipe.

Books

Adverse drug reactions International Reporting of Adverse Drug Reactions. Ed. by ClaMS Working Group. pp. 66. illustrated. SFr. 10. Geneva: WHO. 1990.Human anatomy Basiese Menslike Anatomie. Ed. by Linda de Jager. pp. 204. illustrated. Wetton: Juta. 1990

Planetary landing: modelling and control of the propulsion descent

In the propulsive phase, after parachute release, of planetary landing like Mars or Moon, horizontal motion is obtained by tilting the axial thrust, so that it aligns either to the negative velocity vector (gravity turn) or to the requested acceleration vector. The latter strategy is assumed here, as it allows pinpoint landing. As such, tilt angles (pitch and yaw) become proportional to the horizontal acceleration. Instead of designing a hierarchical guidance and control in which horizontal acceleration becomes the attitude control target, a unique control system can be designed based on the fourth order dynamics from angular acceleration to position. The paper shows that the combined dynamics can be (quasi) input-state linearized except the nonlinear factor of the tilt angles (the axial thrust imposed by vertical braking). The paper shows that control design around the reference trajectory (tilt and position) given by the guidance can exploit the quasi linearization, but tracking error stability must be proved in presence of a not stabilizable external disturbance. The paper is restricted to closed-loop control strategies, and their effectiveness is proved through Monte Carlo simulations

Comparison of Degradation Gradients of a Conventional vs a High Pressure Grazing System

Grazing management is important for general ecosystem health and sustainable livestock production. Historic grazing practices caused grassland degradation. Regenerative grazing practices can improve soil and plant health. This study aimed to determine if a high pressure grazing approach, in fact improves soil and plant health, compared to a conventional grazing system. A degradation gradient (away from watering places) approach were followed. The study site is situated in the Kalahari bushveld bioregion of the North West province of South Africa. Two adjacent farms were selected, one practicing a conventional four camp rotational grazing system, and the other practicing high pressure grazing with 50 camps in a radial layout. Plant species composition and soil properties (carbon, root biomass, minerals) were measured at three increasing distances away from the water. The results indicated an increase in veld condition away from the water in the conventional system, while the veld condition decreased slightly in the high pressure grazing system. Soil properties for the conventional system did not vary much at increasing distances away from the water. At the high pressure system, soil health was slightly better closer to the water. Soil health was generally better at the high pressure system, than at the conventional system. These results indicate that a high pressure grazing approach, where high animal numbers graze an area, evenly, for a short period of time, followed by a long resting period, is more beneficial to plant and soil health, than a conventional grazing approach where lower animal numbers, graze bigger areas for a longer time period. In the Kalahari bushveld of the North West province of South Africa, high pressure grazing systems has the potential to regenerate soil- and plant health

Defoliation Impact on the Above and Belowground Productivity of \u3cem\u3eFestuca arundinaceae\u3c/em\u3e Schreb

The main objective of pasture management is to maximize plant productivity and ensure sustainable animal performance, without inducing pasture deterioration. Many researchers indicated that plant survival and sustainable production is a function of seedbed preparation, irrigation and defoliation, with defoliation having the largest impact on plant persistence (Fulkerson and Donaghy, 2001). The net effect of defoliation (degree of intensity and frequency) can therefore either be beneficial or detrimental to survival and productivity of a pasture. The aim of this study was to quantify the impact of different intensities and frequencies of defoliation on above- and belowground phytomass production of the cultivated pasture Festuca arundinaceae Schreb. under irrigation

Potential of South African entomopathogenic nematodes to control the leaf miner, Holocacista capensis (Lepidoptera: Heliozelidae)

The Cape grapevine leafminer, Holocacista capensis, a sporadic pest of economic importance, is found in South African table and wine grape vineyards. The cocoon casings, constructed by the final instar larvae, can be found attached to grape bunches, posing a phytosanitary risk for table grape export markets. The current study aimed to determine the susceptibility of leaf-mining H. capensis larvae toseven entomopathogenic nematode (EPN) species belonging to Steinernematidae and Heterorhabditidae.  To determine nematode virulence occupied leaf-mining galleries were extracted from infested leaves and inoculated with 200 infective juveniles (IJs) in 50 μl of distilled water, for each of the EPNs screened.Concentration assays were conducted and and lethal dose was determined for the three most virulent species (Heterorhabditis baujardi, H. indica and H. noenieputensis), using concentrations of 0, 25, 50, 100, 200, and 400 IJs/leaf-mining larva. High mortality of leaf-mining larvae was obtained with H. baujardi(92%), H. noenieputensis (85%) and H. indica (83%). Almost double the number of H. noenieputensis (34 nematodes/insect) penetrated the insect larvae, in comparison with the other two EPNs. However, the relative potency of H. baujardi was 3.56 times higher than for H. indica, whilst that of H. indica was 2.57times higher than it was for H. noenieputensis. The results obtained in the laboratory were found to be encouraging, especially with regard to the nematodes’ ability to penetrate the leaf-mining galleries, and to infect the larvae successfully