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There is a general paucity of studies concerning trophic interactions between zooplankton and Cyanobacteria, and about the general role which zooplankton play in pelagic food webs in tropical saline lakes. Although the relative importance of allochthonous and autochthonous carbon resources to the diet of zooplankton in temperate lakes is well understood, significant knowledge gaps remain in tropical systems. This thesis addresses three principal questions: (1) What are the principal trophic interactions between zooplankton and Cyanobacteria in tropical lakes, with a specific focus on the lakes of the East African Rift Valley?; (2) Is there potential for competition between zooplankton and lesser flamingos in the Rift Valley lakes?; (3) What is the relative importance of allochthonous versus autochthonous carbon sources for aquatic consumers in tropical lakes? These questions were answered by analysing the compositions and trophic interactions in the pelagic food webs of four contrasting East African lakes (Naivasha, Baringo, Bogoria and Sonachi). The lakes were sampled over two campaigns in different seasons. The planktonic compositions and size distributions were assessed by microscopic identification of individual planktonic taxa. Fish and flamingos were also sampled. The trophic levels and potential dietary interactions of each identified taxa were then evaluated using natural abundance stable isotope analyses (δ13C and δ15N). The potential contribution of other carbon sources, such as terrestrial particulate organic carbon, was also assessed. In Chapter 3, observations from Lake Sonachi suggest that the pico-alga Synechococcus sp. was the dominant food item for the principal zooplankton taxon (the large calanoid Lovenula sp.). This finding differs from reports in other in tropical lakes which had suggested that large calanoids mainly consume colonies of Microcystis sp. The findings from Lake Bogoria, presented in Chapter 4, suggest a pronounced seasonality in the occurrence of Moina sp. and Cyclotella sp. This was predominantly a consequence of lake level rise and associated freshening during the wet season. These organisms do not appear to be utilised as a significant food source by flamingos in this lake. This suggests that seasonal shifts in the planktonic food web structure are not beneficial for flamingos in this lake. The results also suggest that rotifers may compete with flamingos for their main food item, the Cyanobacterium Arthrospira sp. In Chapter 5, stable isotope abundance and C/N ratio data from Lakes Baringo and Naivasha suggest that pelagic zooplankton in both lakes were largely dependent on autochthonous carbon in both sampling seasons, despite potentially large catchment sediment fluxes. This challenges previous suggestions that allochthonous carbon is an important basal resource for pelagic food webs in many lakes. Such assumptions, as derived from temperate lake systems may not always apply to tropical lake systems, as sampled in this study.

This thesis reports results of a research study into the usefulness of a user-centred approach for designing information retrieval interfaces. The main objective of the research was to examine the usability of an existing Web-based IR system in order to design a user-centred prototype Web interface. A series of usability experiments was carried out with the Web of Science. The first experiment was carried out using both novice and experienced users to see their performance and satisfaction with the interface. A set of search tasks was obtained from a user survey and was used in the study. The results showed that there were no significant differences in the time taken to complete the tasks, and the number of different search terms used between the two search groups. Novice users were significantly more satisfied with the interface than the experienced group. However, the experienced group was significantly more successful, and made fewer errors than the novice users. The second experiment was conducted on novices' learning and retention with the Web of Science using the same equipment, tasks and environment. The results of the original learning phase of the experiment showed that novices could readily pick up interface functionality when a brief training was provided. However, their retention of search skills weakened over time. Their subjective satisfaction with the interface also diminished from learning to retention. These findings suggested that the fundamental difficulties of searching IR systems still remain with the Web-based version. A heuristic evaluation was carried out to find out the usability problems in the Web of Science interface. Three human factors experts evaluate the interface. The heuristic evaluation was very helpful in identifying some interface design issues for Web IR systems. The most fundamental of these was increasing the match between system and the real world. The results of both the usability testing and the heuristic evaluations served as a baseline for designing a prototype Web interface. The prototype was designed based on a conceptual model of users' information seeking. Various usability evaluation methods were used to test the usability of the prototype system. After each round of testing, the interface was modified in accordance with the test findings. A summative evaluation of the prototype interface showed that both novice and experienced users improved their search performance. Comparative analysis with the earlier usability studies also showed significant improvements in performance and satisfaction with the prototype. These results show that user-centred methods can yield better interface design for IR systems.

An assessment methodology has been developed for - use during the conceptual/preliminary design phase to quantify the effectiveness of newly designed aircraft. The effectiveness is measured by a squadron Sortie Generation Rate (SGR). Key elements of this methodology were the establishment of link parameters between design synthesis and the main effectiveness disciplines. These were Reliability and Maintainability (R&M), Survivability/Vulnerability and Acquisition Cost. A programmable solid modeller was used to create a solid CAD assembly of the aircraft critical components. A ray tracing technique has been used to develop an interactive vulnerability assessment tool. A Mission Simulation Model (MSM) has been developed which typically simulates the operation of a squadron of aircraft and gives the operational activities such as flying sorties and maintenance actions. The methodology has been validated based on real data from recent conflicts. The application aspects of the methodology have been demonstrated by quantifying the effectiveness of two recent combat aircraft.

Injecting drug use worldwide accounts for a high proportion of new Human Immunodeficiency Virus (HIV) infection, driving the national epidemics in many countries where HIV prevalence among injecting drug users (IDUs) is prominent. HIV testing started in Vietnam in 1988 and the first HIV case was detected in 1990. The epidemic has now concentrated among young IDUs in northern Vietnam. Hai Phong is one of the provinces located in the north of Vietnam which has become a high HIV prevalence province affecting young IDUs. The present research estimates HIV infection rates among IDUs in Hai Phong. It examines behavioural risk factors associated with HIV infection, sharing and condom use as well as highlighting drug and sex related transmission risks. The research has several stages including secondary analysis of national level behavioural survey data (2011) and qualitative exploratory research (2012). Each phase of the research supplements the others, in order to attain the research objectives and to address behavioural issues associated with the current epidemic.