Assessing the spatio-temporal climate variability in semi-arid Karamoja sub-region in north-eastern Uganda

Semi-arid areas show climatic variability on a spatio-temporal scale. There are few studies on the long-term trends and intensity of this variability from East Africa. We used National Ocean and Atmospheric Administration re-analysis climate data (1979–2009) in this study. Rainfall exhibited a non-significant long-term trend. The climate of the area is variable (coefficient of variation-CV?>35.0%) with spatio-temporal oddities in rainfall and temperature. A rise in minimum (0.9?°C), maximum (1.6?°C) and mean (1.3?°C) temperature occurred between 1979 and 2009. There were more months with climate variability indices below the threshold (<1.0) from 1979 to 1994 than between 1995 and 2009, with wetness intensity increasingly common after 2000, leading to the observed reduction in the recurrence of multi-year drought events. More extreme wet events (rainfall variability index?>2.6) were experienced between 2004 and 2009 than between 1984 and 2003. We consider that the use of spatio-temporal climatic information for timely adjustment to extreme climate variability events is essential in semi-arid areas.     

Mass-Production Methods in Depositing Nickel at High Current Density

Practical proposals are put forward for reducing unit costs in the painting of automobiles. Suggestions cover increased production, raising first-time OK rate, reducing electroprimer usage and eliminating waste, electrostatic surfacing, reduction of wet sanding costs.     

Problems in High Current Density Nickel and Chromium Deposition

Five optical methods are discussed here by which the surface finish of polished or electrodeposited metal surfaces may be studied. Four are dealt with briefly because they have been adequately described in the literature. The fifth is believed to be new in its application to metal finishing. Preliminary results obtained for polished brass surfaces and for various electrodeposited metal coatings are discussed.

The presence of an oxide film has a marked influence on the optical behaviour of a metal surface. The properties of such a film may be learnt from the methods here outlined. Of particular practical interest is the anodic oxide film, familiar long since as a surface finish for aluminium and of current interest as a possible protection for other metals. The methods described are of general application. Illustrations are provided of the results obtained on anodised tantalum surfaces.     

The responses of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in Lake Wamala (Uganda) to changing climatic conditions

Changes in the catches of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), in Lake Wamala (Uganda) have been observed since its introduction. The factors contributing to these changes, however, are not well understood. This study examined changes in species composition, size structure, size at first maturity, length–weight relationship and condition factor of Nile tilapia in Lake Wamala, in relation to changes in temperature, rainfall and lake depth, to provide a better understanding of the possible role of changing climatic conditions. There was an increase in the minimum, maximum and average temperatures since 1980, but only the minimum (0.021 °C year^?1) and average temperatures (0.018 °C year^?1) exhibited a significant trend (P < 0.05). Rainfall increased by 8.25 mm year^?1 since 1950 and accounted for 79.5% of the water input into the lake during the period 2011–2013, while evaporation accounted for 86.2% of the water loss from the lake. The lake depth was above 4 m during the years when the rainfall exceeded the average of 1180 mm, except after 2000. The contribution of Nile tilapia to total fish catch and catch per unit effort (CPUE) increased with rainfall and lake depth up to the year 2000, after which they decreased, despite an increased rainfall level. The lake depth was positively correlated with the average total length and length at 50% maturity (r = 0.991 and 0.726, respectively), while the slopes of the length–weight relationships differed significantly between high and low lake depths [t₍₆₎ = 3.225, P < 0.05]. Nile tilapia shifted from an algal‐dominated diet during the wet season to include more insects during the dry season. The results of this study indicate Nile tilapia in Lake Wamala displays a typical r‐selected reproductive strategy, by growing to a small size, maturing faster and feeding on different food types, in order to survive high mortality rates under unfavourable conditions attributable to higher temperatures, low rainfall and low lake water levels.