Showing papers by "University of Johannesburg published in 1996"

The role of zinc in magnetic and other physical water treatment methods for the prevention of scale

Abstract: line species released from the surface of physical water treatment devices into the feed water are shown to be primarily responsible for scale inhibition effects observed in three different types of physical water treatment (PWT) devices. The three types of PWT devices included units based on a magnetic field provided by a permanent magnet; a high frequency electric field; and a catalytic conversion process. Freshly released zinc from PWT devices was shown to have a marked effect on the induction period for CaCO, precipitation and on the crystal morphology of CaCO 2 . No measureable effect on the crystallisation reaction for calcium carbonate ascribable to the magnetic or electrical fields caused by the devices under investigation could be found.

Inter- and intraspecific allozyme comparisons of mormyrids (Pisces, Mormyridae) from South Africa and Namibia, with reference to an undescribed species

Abstract: Allozyme comparisons of allopatric populations of Marcusenius macrolepidotus and Petrocephalus catostoma (from the eastern Caprivi, Namibia, and the Kruger National Park, South Africa) showed little differentiation between the populations of the former species mentioned, but distinct differences between the two populations of P. catostoma studied. Three continuous and two discontinuous buffer systems were used, and gene products of 26 protein coding loci were examined by horizontal starch gel-electrophoresis. Fixed allele differences between M. macrolepidotus and P. catostoma were obtained at 13 of these loci. Allele frequency differences were found between allopatric populations of the former species, whereas distinct allozyme differences were found at seven of the loci studied in the latter species. This, together with the mean genetic distance value of 0.311, suggests the existence of an undescribed P. catostoma species from the Sabie River system. The unbiased genetic distance value among the M. macrolepidotus populations studied was 0.023, and it averaged 0.927 between the confamilial genera Marcusenius and Petrocephalus.