Life-table experiments with Helisoma duryi (Wetherby) and Biomphalaria Pfeifferi (Krauss) at constant temperatures

In an effort to find an ecological homologue that could be utilized as a biological control agent of the intermediate host species of economically important helminth parasites, age-specific life-table experiments with Helisoma duryi (Wetherby) ind Biomphalaria pfeifferi (Krauss) (intermediate host of Schistosoma mansoni) were carried out at a series of constant temperatures in a laboratory. The results showed that the lifespan and net reproduction rate of H. duryi were higher than those of B. pfeifferi over the whole range of temperatures investigated (18-35°C). The conclusion is reached that H. duryi should theoretically be capable of establishing viable populations in most of the habitats occupied by B. pfeifferi in South Africa

Geographical distribution and habitat preferences of the invader freshwater snail species Lymnaea columella (Mollusca : Gastropoda) in South Africa

The present geographical distribution of Lymnaea columella, as recorded in the National Freshwater Snail Collection, is described and discussed. It appears that L. columella is the most successful colonist of all the freshwater snail species in South Afnca, and, together with Bulinus tropicus and Lymnaea natalensis, it forms the most widely distributed freshwater snail species in the region. Data regarding the 2 341 discovery sites of L. columella recorded by collectors during surveys are analysed. L. columella cluster mainly in rivers or streams with perennial, slow flowing , or stagnant freshwater with many plants and a mud substrate. L. columella is regarded as a more effective intermediate host for the transmission of fascioliasis than the indigenous snail species. The economical implications of this are discussed briefly in the light of its success as an invader species.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

The occurrence of Schistosoma mattheei in the south-western Transvaal

To determine whether Schistosoma mattheei is present in the south-western Transvaal, sixty habitats were searched for the intermediate host snail, Bulinus africanus. Ten populations of this snail were located, 2 of which were infected with S. mattheei. Eggs of one of these isolates, originating from a spring in the Mooi River, were examined with an optical microscope. Scanning electron micrographs of the teguments of adult male worms and the terebratorial membranes of miracidia are described. These parasites are morphologically similar to some previously described from another habitat in the same geographical area and both populations can be regarded as typical S. mattheei.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

The tegument of Schistosoma hippopotami from Hippopotamus amphibius in the Kruger National Park

Schistosoma hippopotami were collected from the right heart chambers and pulmonary arteries of Hippopotamus amphibius culled in the Kruger National Park. The schistosomes were subjected to scanning electron microscopy as well as optical microscopy. The results indicate that S. hippopotami is not conspecific to S. mansoni as suggested in the literature. On account of the morphology of certain tegumental structures of both male and female parasites, it is suggested that S. hippopotami is adapted to the pulmonary arterial circulation of its host.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Notes on the occurrence of tubercular spines in Schistosoma margrebowiei and Schistosoma mattheei

Scanning electron microscopical (SEM) studies on tegument of the bovid schistosomes, Schistosoma margrebowiei and Schistosoma mattheei have yielded conflicting results; certain authors observed the tubercles on the tegument of these species to be spined, while others reported that they are spineless. The present study indicates that the protrusion of tubercular spines is subject to phenotypic plasticity regulated by external factors such as the identiy of the host species and whether or not the schistosome is paired.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Survival of Bulinus africanus (Krauss), Bulinus globosus (Morelet) and Biomphalaria pfeifferi (Krauss) at constant high temperatures

The survival of the freshwater snail species Bulinus africanus, Bulinus globosus and Biomphalaria pfeifferi at extreme high temperatures was experimentally investigated. Snails were exposed to temperatures in the range from 34°C to 40°C and their survival was noted daily. The results showed that the survival of the cohorts of all three species decreased with increased temperatures. It was also found that B. globosus survived longer at high temperatures than B. africanus and B. pfeifferi. There was no marked difference between the survival of the latter two species

The effect of constant low temperatures on the survival of Bulinus africanus (Krauss), Bulinus globosus (Morelet) and Biomphalaria pfeifferi (Krauss)

The tolerance to low temperature of the freshwater snail species Bulinus africanus, Bulinus globosus and Biomphalaria pfeifferi was experimentally investigated. Snails were exposed to temperatures ranging from 0 °C to 8 °C and their survival was noted daily. The results showed that the survival of the cohorts of all three species decreased as the temperature was lowered in the range investigated. Evidence is presented which demonstrates that B. africanus can withstand cold conditions better than B. globosus, and that B. globosus is better equipped than a pfeifferi in withstanding low water temperatures

Nanoparticles and Organic Semiconductors for Flexible Electronics

Key issues for flexible electronics are low temperature processing, cost-efficient semiconducting and dielectric materials, and sufficient performance of the integrated TFT devices. To achieve high performance flexible circuits, contact resistances of today’s transistors must be reduced. Additionally, the parasitic overlap capacitances between the transistor’s electrodes need to be minimized. The inverted staggered transistor setup with self-aligned gate fulfills these requests. Nevertheless, the integrated devices suffer on poor AC characteristics due to limited performance of the common gate dielectric layers. The gate voltage has no direct access to the semiconductor surface, either due to rechargeable surface states and polarization effects or because of low-k values. Consequently, new flexible high-k dielectrics must be implemented in TFT device integration