The electrocatalytic activity of a bimetallic
Pt0.5Ru0.5N(Oct4)Cl
colloid toward the oxidation of CO and
a CO/H2 gas mixture (simulated reformer gas) was measured.
The particle size distribution with a mean
diameter of 1.7 ± 0.5 nm was determined by high-resolution
transmission electron microscopy, and the
formation of stoichiometrically alloyed particles was verified by
point-resolved energy dispersive X-ray
analysis. The CO-stripping voltammetry of glassy carbon supported
Pt0.5Ru0.5 clusters was found to
be
in excellent agreement with CO-stripping voltammetry data measured on
well-characterized bulk alloy
electrodes. The activity of the colloid toward the continuous
oxidation of 2% CO in H2 was assessed in
a rotating disk electrode configuration at 25 °C in 0.5 M
H2SO4, leading to the conclusion that PtRu
colloids
are a promising route toward the preparation of bimetallic
high-surface-area fuel cell catalysts.
The effect of different photoperiod regimes, as well as cover in continuous light (24L/0D) and darkness (OL/24D), on the growth rate of larval Clarias gariepinus was evaluated. In addition, a behavioural study of the effect of light on larval and juvenile C. gariepinus was made. The growth rate of larvae was found to increase with shorter light periods, the highest being recorded in continuous darkness (0L/24D photoperiod). Cover was found to enhance the growth rate of larvae reared under a continuous light period, however, the presence of cover did not affect the growth rates of larvae reared in continuous darkness. The behaviour of larval and juvenile catfish differed markedly in continuous light and darkness. When subject to a continuous light period, a strong negative phototaxis, long rest periods interspersed with disturbed activity, refuge seeking behaviour, and increasing incidence of territorial aggression were observed. In continuous darkness, the fish displayed a high level of active swimming with fewer rest periods, and a lower incidence of disturbed rest activity. The level of territorial aggression among fish in continuous darkness gradually declined and became negligible. Higher levels of browsing and airbreathing activity were observed in continuous darkness than in light. The present results, interpreted together with other ecological and anatomical data, demonstrate this species to be primarily a nocturnally active, tactile feeder, with a distinct diet activity pattern. The refuge seeking behaviour observed in the light is interpreted as an adaptation to avoid predators that rely on sight to detect prey. This behaviour, however, appears to promote intraspecific competition for refuges, resulting in a high degree of territorial aggression, and probably an increase in the rate of cannibalism. With regard to fish culture, it is suggested that the rearing of larvae in conditions of continuous darkness or low light intensity is optimal owing to the higher growth rates and apparent reduction of stress observed under these conditions.
The contribution of inland fisheries to food security, livelihood provision, poverty alleviation, and economic development in developing African countries is well documented, but there is surprisingly little literature on the history, current status and potential of South Africa's inland fishery resources. This presents a constraint to the management and sustainable development of inland fisheries. A literature review of peer-reviewed and grey literature was thus undertaken which is presented as a synthesis of knowledge on inland fisheries in South Africa. We track the chronology of literary themes on inland fisheries from the colonial era to the present, provide an overview of the recreational, subsistence and commercial sub-sectors, the production potential of inland waters, interventions to promote fishery development, and attempts to value inland fisheries. The review summarises the current state of knowledge on fisheries resources, outlines potential sources of data, highlights relevant and important information, and identifies knowledge gaps. The literature survey reveals an urgent need for research covering the biological, social, economic and governance aspects, if inland fisheries are to be developed in a rational and sustainable manner which promotes South Africa's national policy goals.
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