Maize (Zea mays L.) is ranked as the third most important food crop by production globally, after rice and wheat. Several biotic (diseases, pests) and abiotic (unfavorable climatic conditions) factors affects its production. Maize lethal necrosis (MLN) disease outbreak within East Africa threatens production of maize. Information on interactions of viruses causing MLN with plant parasitic nematodes is lacking. This study was carried out to determine i) the effect interaction of of plant parasitic nematodes with viruses causing MLN on disease development in maize fields and ii) the effect of lesion nematodes (Pratylenchus spp.) on MLN disease development in the greenhouse. For the field study, four counties in Kenya were visited, farms selected at random, MLN scored and both maize leaf and soil samples collected and analyzed for presence of viruses causing MLN disease and for parasitic nematodes. Snowball sampling or chain-referral sampling technique was used to sample MLN infected farms across the selected regions. Variance analysis was used to measure significant differences (P< 0.05) in MLN disease incidence and severity due to interaction between viruses and nematode populations. In the greenhouse study, two maize varieties, were used H614D and Emph 1101. Variety H614D is known to be susceptible to both MLN and Pratylenchus spp. whereas maize variety Emph 1101 is susceptible to MLN but resistant to Pratylenchus nematodes. The two maize varieties were subjected to three distinct treatments: single inoculation with MCMV and SCMV; combined MCMV + SCMV inoculation; the third treatment was the addition of Pratylenchus nematodes to the previous two treatments. Disease severity and incidence were recorded weekly over a period of two months. xiii Survey results indicated no significant effect of combined infestation of parasitic nematodes (Pratylenchus spp., Tylenchus spp., Meloidogyne spp. and Helicotylenchus spp.,) on MLN disease severity in the field. However, there was significant effect of Pratylenchus to MLN severity in the greenhouse experiment. The development of MLN disease in maize varieties Emph 1101 and H614D infected with Pratylenchus spp. nematodes was studied under a greenhouse experiment. MLN disease severity was higher in H614D than in Emph 1101. Plants inoculated with MLN+Pratylenchusrecorded a significant difference across the two varieties on area under disease progress curve (AUDPC). There is need for nematodes management even though the field experiment indicated no significant effect of parasitic nematodes on MLN disease developement. There is also need for an open field study to evaluate the effect of Pratylenchus spp. on the development of MLN disease.

Farming as a source of income for rural households has failed to solely sustain livelihoods. Consequently, there has always been a need for diversification into off-farm activities and which often is not a panacea. Livelihood diversification is seen as a coping strategy for most rural households, although there is limited empirical evidence that shows if' and even why' the households diversify. Furthermore, little is known about the effect of diversification on agricultural production and household income. This study examines the factors influencing livelihood diversification and its effects on agricultural production and household income in Nyamira County, Kenya. Cross-sectional data were collected through semi-structured questionnaires involving 120 households. The first objective of the study was to assess the factors that influence the choice of different livelihood strategies in the study area; the second was to assess the effect of livelihood diversification on agricultural production while the third was to determine the contribution of off-farm income on the total household income of residents in the study area. Multi-stage sampling technique was used whereas the sample size was determined by the use of proportionate to size approach. Both descriptive and inferential statistics were used to analyse the collected data. Seven livelihood strategies adopted in the study area were identified. The most popular off-farm livelihood strategy was casual labour in the agricultural sector and the least was rents. Poisson regression results suggest that; average years of schooling of other household members, number of household members with secondary education, time taken to the water source (P=0.002), access to extension services (P=0.036), group membership (P=0.001) and electricity access (P=0.000) were the factors that influenced the number of livelihood strategies a household selected. Off-farm income accounting for about 44 percent of household income had an effect on agricultural production through the purchase of inputs used in the farm. In conclusion, both farm and off-farm sectors of the rural economy are important in sustaining livelihoods thus efforts towards enhancing both sectors should be put in place. Also, farming households in the study area need to diversify their livelihood sources to increase their cash earnings and to well utilize the existing production resources. To enhance livelihood diversification, the government, both the National and County government, should improve rural infrastructure in terms of provision of electricity and construction of tap water points near homes of people especially in hilly areas of the County.

Admixtures are used to improve the properties of concrete or mortar to make them more suitable to work by hand or for other purposes such as saving mechanical energy. Retarding admixtures are used to slow the rate of setting of concrete. By slowing the initial setting time, the concrete mixture can stay in its fresh mix state longer before it gets to its hardened form. Retarders can be formed by organic and inorganic material. The organic material consists of unrefined CaO, K2O, MgO, AL2O3, salts of lignosulfonic acids, hydroxycarboxylic acids, and carbohydrates. Agave sisalana Perrine, popularly known as sisal is a commercially used fiber yielding plant. Cement concrete production especially in hot climate experience a lot of challenges from mixing, transporting and placing of concrete because of the accelerated setting of cement concrete due to high temperatures. Workability is compromised to a large extend and there is need to prolong the setting time allow for execution of the concreting activities. The rapid heat generation from large concrete pours can also lead to cracks in the concrete structure. This results in the need to slow the rate of concreting thereby causing costly delays. Retarders go a long way in slowing down the hydration process hence reduce the heat of hydration. The study investigated the suitability of sisal juice as a retarder to influence the properties of hardened concrete at a lower cost. This research implored the use of experimental design. The study used quantitative techniques of data analysis to analyze the test results of different experiments. Descriptive statistics including means, cross-tabulation, frequencies and percentages was used for comparison and the results presented in form of frequency tables, line graphs and bar charts for easier understanding and interpretation. SJE was used as a retarder to influence the properties of fresh and hardened concrete. Sisal juice extract was used as a partial replacement of water at different dosages and in the concrete mix. A total of 84 concrete cubes were produced in 7 sets of 12no. specimen each. One set was made with the control mix which had zero SJE content. The remaining sets had varying dosages of SJE namely 5%, 10%, 15%, 20%, 25% and 30%. Twelve beam specimens measuring 150x150x530mm were also casted. Specimens were subjected to Compressive strength tests as per BS EN 12390–3:2009, setting time test as per BS EN 196-3:1995 and slump test as per BS EN 12359–2:2009. To establish the effect SJE on strength of concrete, compressive strength was tested at 7, 14, 28 and 56 days while flexural strength

This study evaluated the morphological and anatomical responses of below-ground parts of Pennisetum mezianum, Digitaria macroblephara,and Themeda triandra to moisture variation in the semi-arid rangelands of South Eastern Kenya. Bud and root functional traits, including average root diameter (RD), root tissue density (RTD), specific root length (SRL), percent root dry matter content (PRDM), and non-structural carbohydrates (NSC) were determined.Soil moisture content below the ground surface was monitored to determine its relationship with the aforementioned parameters. Decline in soil moisture caused significant (p<0.05) decrease in bud size, PRDM, and increase in NSC for all three grass species. Generally, RTD increased with increase in soil moisture deficit in all three grass species. For SRL, it significantly increased with a decrease in soil moisture content in D. macroblephara. There was no significant variation in the average number of buds and RD, with corresponding variation in soil moisture content. Pennisetum mezianum had significantly (p<0.05) higher number of buds, largest bud sizes, largest RD, lowest SRL, lowest RTD, and least amount of NSC content. Themeda triandra and D. macroblephara had a narrow root diameter, high SRL, high RTD, and a high NSC content. These patterns indicate that the three grass species had developed diverse strategies to withstand water deficit conditions, with P. mezianum employing a conservative strategy, while T. triandra and D. macroblephara employ a timely utilization strategy. Further research should be conducted on more range grass species over multiple seasons to better understand adaptive mechanisms of range grass species to enable us to predict plant community change because of climate change.

Globally, attention has been focused on pollution and exhaustion of fossil fuels allied to conventional energy sources. In contrast, non-conventional energy/renewable energy sources have always been considered clean and environmentally friendly. The non-conventional (renewable) are being preferred because they are believed to be more environmentally friendly. Renewable Energy Technologies (RETs), especially Solar Photovoltaics, have seen many plants being constructed to supplement the grid or alternatives for those far from the grid. Solar Photovoltaics plants occupy large tracts of land, which would have been used for other economic activities for revenue generation such as agriculture, forestry, and tourism in archaeological sites. The negative impacts slow down the application of Solar PV. Still, a modeling tool that can quickly and quantitatively assess the effects in monetary form would accelerate the Solar PV application. This thesis presents a developed modeling tool that determines not only the techno-economic impacts but also the environmental impacts in monetary form for one to be able to assess the viability of a plant in a given region. Solar-PV based Power and Environmental Cost Assessment (SPECA) model was developed to help in the following ways: (i) understanding of Solar PV based power generation and its interactions with the resource inputs, the private costs, externalities, external costs, and hence the environmental and social-economic impacts over the lifespan of the plant (ii) aiding investors of Solar PV with a tool which has a clear graphical and user interface for detection of the main drivers of the Levelized Cost of Energy (LCOE) (iii) creating an enabling environment for decision-makers aided by a visual SPECA modeling tool which takes into account the financial viability and the environmental impacts of Solar PV. SPECA is a sizing tool for techno-economic analysis. It is mathematically based, capturing all the life cycle costs and their associated ecological burdens. The source codes of the SPECA model have been written in Visual Basic programming, while the Database was developed using the Standard Querry Language (SQL). The modeling tool provides a friendly Graphical user interface where the user can input the required data. In general, SPECA will be of great use to investors and policymakers of Solar PV systems for drawing alternatives and conclusions based on the best compromise. The model developed will be useful, especially in addressing the trade-offs between environmental impacts and financial impacts, which aim to improve the quality and transparency in the decision-making during the deployment of Solar PV. The quantification of the social-environmental effects of Solar PV will permit for cost accounting assessment of the unforeseen cost incurred when using them for electricity generation. The SPECA modeling tool presents the LCOE, the Levelized Total Cost of Energy (LTCOE), and the Levelized Externality Cost of Energy

Smallholder farmers in East Africa generally intercrop maize (Zea mays L.) with grain legumes to intensify cropping, improve soil fertilizer, reduce pests and disease pressure, and control weeds. However, the compatibility of maize with the majority of legume species is only partiallyunderstood, particularly with regards to yield-limiting factors that arise from the intra-specific competition. Intraspecific competition between maize and legumes could be alleviated through both the spatial and temporal arrangement of the companion crops. On the other hand, legumes are frequently integrated into push-pull crop arrangements to suppress field pests in maize such asthe stalk borer and lately the fall armyworm. However, the push-pull technology predominantly integrates non-food legumes such as desmodium but evidence shows that food legumes are also effective in manipulating the pest habitat. In addition, the use of food and perhaps dual-purpose legumes could be more attractive to farmers in comparison with the use of desmodium. Further, the efficiency of this technology could be improved through the temporal arrangement of maize and legumes, particularly by relaying maize into established legumes, albeit with knowledge limitations. In the context of these knowledge gaps, a study was carried out with two objectives: (1) to evaluate the compatibility of maize with a diverse range of legumes species in both simultaneous and relay intercrop system; and (2) to assess the effect of simultaneous and relay intercropping of maize with different legumes species on the suppression of Fall armyworm (Spodoptera frugiperda) in maize. Field experiments were carried out at the Kenya Agricultural and Livestock Research Organization (KALRO) in Kiboko and the Kabete farm of the University of Nairobi. In each site,two experiments were carried out, and both experiments consisted of nine legume species: common bean (variety Rosecoco), pigeon pea (Kat 80), dolichos lablab (DL1002), groundnut (ICGV 9704), soybean (SB19), green gram (N26), cowpea (M66) and green leaf desmodium, in addition to sole maize as control. In the first experiment, crops of maize and legumes were sown simultaneously while in the second trial maize was relay cropped into established legumes. Both experiments were laid out in a randomized complete block design and replicated three times. In the maize-legume compatibility study, measurements included crop growth traits, yield components and intercropping productivity indices while the second objective comprised leaf feeding damage, dead heart incidence, ear damage rating, and the number of pest larvae, as well as yield components. Analysis of variance showed significant differences among treatments (p≤ 0.05) in maize-legume compatibility and fall armyworm infestation. Intercropping maize with pigeon pea, lablab in relay cropping system in Kabete, significantly (p≤ 0.05) increased yield by 35% and 70% respectively whereas in simultaneous cropping system in Kabete, desmodium and beans increased maize stand count at harvest by 17.6% and 18.5%, respectively. At the same site, simultaneous intercropping of cowpea recorded significantly the highest maize stand count at harvest (113 plants per an area of 180m2) than relay cropping system at (89 plants at the same area). Similarly, in Kiboko, simultaneous intercropping of maize with green gram, lablab recordedthe highest maize stand count at harvest by 35 and 40 plantsrespectivelymore than relay croppingsystem. In addition to fall armyworm (FAW) infestation data, simultaneous intercropping of maizewith cowpea, lablab, bean, and desmodium significantly (P ≤0.05) reduced FAW damage in maizeleaf by 46.6, 47.0, 73.0, and 73.1% respectively at both vegetative and flowering stage at the twosites. Relaying maize into established cowpea, lablab, beans and desmodium significantly (P≤0.05) reduced FAW infestation in maize leaf by 65.9, 75.6, 78.0 and 87.8% respectively from vegetative to the flowering stage at both sites. More ever, establishing maize simultaneously witheither lablab, green gram, beans and desmodium significantly (P ≤0.05) reduced the number of FAW pest larvae in maize plant by 42.6, 69.6, 70.0, and 87.0% respectively in all physiological stages across the two sites. Similarly, relay establishment of maize into lablab, cowpea, beans, and desmodium significantly (P ≤0.05) reduced the number of FAW pest larvae in maize plant by 62.2, 70.0, 77.8, and 100% respectively in all stages of growth in both sites. In this study, relaying maizeinto an already established lablab, bean and desmodium reduced FAW infestation or damage on maize plants at nearly all physiological stages compared with other legumes in all the sites. In conclusion, when comparing means of lablab and bean with desmodium, it shows there are no significant differences between those three legumes. Therefore, it is highly recommended to use lablab and bean instead of desmodium in the management of FAW in maize.

Salmonellosis is a major global threat to public health and causes emergence and spread of antimicrobial-resistant strains. This study aimed to determine the prevalence and characterization of Salmonella species (spp.) in retail pork and raw vegetables commonly known as Kachumbari( tomatoes, onions, pepper, dhania, avocados) served alongside cooked pork in Busia County, Kenya. Samples collected from selected butcheries were 451 consisting of 262 raw pork, 108 cooked pork and 81 side salads served alongside cooked pork. Samples were cultured in Salmonella selective media in Busia ILRI laboratories. Isolated Salmonella spp. were afterwards identified using genus antiserum at the UoN laboratories . Serotyping was done using KauffmannWhyte scheme and antimicrobial sensitivity was determined using disc diffusion method. The overall Salmonella prevalence of retail pork was 32.59% (147/451 95% CI 32.40% - 32.80%). Raw pork recorded the highest prevalence of 49.24% (129/262 95% CI 48.86% - 49.61%), followed by raw vegetables with 19.75% (16/81 95% CI 18.79% - 20.72%) and cooked pork recorded the least with 1.85% (2/108 95% CI 1.65% - 2.10%). Salmonella-positive isolates were highly resistant to the antibiotics used with an overall resistance of 135/147 (91.84%). 67/147 (45.58%) of the samples had multidrug resistance while 99/147 (67.35%) had extended drug resistance. Overall, the isolates had the highest resistance to Gentamicin (63.94%) followed by Ampicillin (59.86%). The highest intermediate resistance was found in ciprofloxacin (76.19%) and nalidixic acid (74.15%). Seven isolates were resistant to third-generation cephalosporins, ceftriaxone. This study highlights a risk of exposure to Salmonella spp. from retail pork and raw vegetables sold at pork butcheries in Busia. This is evidenced by the high prevalence of Salmonella spp. from the raw pork and raw vegetables served alongside cooked pork from butcheries in the four sub- xv counties in Busia that were being investigated. In this setting, cooking of pork mitigated much of the risk of exposure to Salmonella spp. from pork, though the practice of plating pork with raw vegetable side-salads (Kachumbari) with a high prevalence of Salmonella spp. is thought to reintroduce the exposure risk. This study is not able to determine if the vegetables entered the butcheries while contaminated or whether they were cross-contaminated within the butchery setting. This is the first study reporting on salmonella prevalence in retail pork in this country. Worryingly the majority of the isolates were resistant to one or more antimicrobials tested and more than half of them had multidrug-resistant to three or more classes of antimicrobials tested, creating an additional potential health burden. This study highlights risks that may be present in other butchers in the country where hygiene and sanitation are not strictly followed hence necessitating more investigation and action to be taken.

Adaptive Noise Cancellation (ANC) entails estimation of signals corrupted by additive noise or other interference. ANC utilizes a “reference” signal correlated in some way with the “primary noise” in the noise cancellation process. In ANC, the reference signal is adaptively filtered and thereafter subtracted from the “primary” input to obtain the desired signal estimate. Adaptive filtering before the subtraction process allows for handling of inputs that are either deterministic or stochastic, stationary or time varying. ANC has been widely applied in the fields of telecommunication, radar and sonar signal processing. The performance and efficiency of ANC schemes is based on how well the filtering algorithm can adapt to the changing signal and noise conditions. It is worthwhile focusing on developing better variants of AI algorithms from the point of view of ANC. This thesis is focused on: development of a modified version of the Simulated Annealing (SA) algorithm and its application in ANC. This is alongside an analysis of the effectiveness of the standard and modified SA algorithms in ANC in comparison to standard Least Mean Square (LMS) and Normalized Least Mean Square (NLMS) algorithms. Signals utilized in this study include: sinusoidal signals, fetal electrocardiogram signals and randomly generated signals. The modified SA algorithm has been developed on the basis of making modifications to the control parameters of the standard SA on the basis of the acceptance probability and the cooling schedule. A low complexity acceptance probability scheme has been proposed. The proposed cooling schedule is iteration-adaptive to improve on algorithm convergence. The ANC problem is formulated as a minimization problem entailing the minimization of the difference between a noise contaminated signal and a weighted estimate of the noise content. This is achieved through optimal ANC tap-weight adjustment. The algorithms under study are applied in the weight generation process with the expected outcome as ideally a noise free signal. In this evaluation, performance measures analyzed in the study are mis-adjustment and convergence rate. To evaluate these, Euclidean distances and the correlation factors between the desired signal

Animal behavioral studies are essential to efficiently manage them and their preferred habitats for the mutual benefit of both. However, very few studies have been conducted on Rothschild’s giraffes’ ethology in Africa, and especially in Kenya. The objective of this study was to assess the seasonal diurnal activity time budget and foraging patterns of free-ranging Rothschild’s giraffes in Lake Nakuru National Park (LNNP), Kenya. The species is under the IUCN Red List, due to a variety of threats and the continued rapid population decline globally. Scan sampling method was used to assess how Rothschild’s giraffes allocate time to various activities of the day. Descriptive data analysis was performed and results presented in bar graphs, and line graphs. Independent t test was performed to compare giraffes’ activities and food preference in different seasons, dry and wet seasons. All statistical tests were considered significant at a 95% confidence limit if type 1 error (alpha) is less than 5% (0.05). Foraging was the principal activity in both dry and wet seasons being allocated 53% and 57% of their time respectively. Resting and movement accounted for 18 and 26%, in dry and wet seasons respectively. Although Vachellia xanthophloea, Maytenus senegalensis, Solanum incanum contributed to the bulk of giraffes’ diet in both seasons, the most preferred woody species was Vachellia xanthophloea in the dry and wet season (67% and 72%) respectively. Other notable plant species that giraffes fed on included Maerua triphylla, Vachellia gerrardii, and Grewia similis during the dry season and Maerua triphylla, Vachellia abyssinica, and Rhus natalensis during the wet season. The most preferred browsing height was about 3.5 meters (level 5) (49% in the dry season and 46% in the wet season) while 1 meter (level 2) was the least preferred (7% in the dry season and 4% in the wet season). At 3 and 3.5 meters (level 4 and 5) giraffes fed on more plant species including Vachellia xanthophloea, Maytenus senegalensis, Maerua triphylla, Vachellia abyssinica, and Rhus natalensis. This study concluded that seasonality does not influence the diurnal activity time budget of Rothschild’s giraffes in LNNP while the hypothesis that Rothschild’s giraffes’ foraging habits vary significantly between the dry and wet seasons was not entirely supported. Giraffes forage and move around when temperatures are low and rest when temperatures are high to conserve energy. The choice of browse species to feed on is an adaptive strategy to survive recurrent droughts, a common occurrence in the study area which is generally Arid and Semi-arid. Giraffes prefer to forage below 4 meters (3.0-3.5), which is within the average body height of an adult giraffe. Planting perennial woody species will promote uniform use of resources in the park, increase the diversity of plant species foraged by giraffes and reduce browsing pressure in acacia woodlands.

Even though the construction industry in Rwanda is growing at an increasing rate due to the enabling political environment that promotes doing business and a booming private sector driven economy, most construction contractors companies in the country remainat same level of survival and growth in business for quite a long period of time due to anumber of hindering factors. This situation is not good for it implies low and/or under developing contracting capacity in the country. The aim of this study is to find outthe challenges which cause failure experienced by the contractors in the execution of roads and bridges construction contracts and to develop a strategy to mitigate the failure. In order to achieve the objectives and aim of the study, an online questionnaire survey of 80 construction contractors, 58 consultancy firms and 32 clients was conducted.The researcher surveyed 30 causes of contractor’s failure that had been categorized, from review of the related literature, into four groups: (i) managerial causes; (ii) financial causes; (iii) expansion causes; and (iv) external causes. The respondents rated the factors on a 5 point scale, indicating the relative level of impact on the contracting firmto cause failure. In the data analysis, the causes were ranked according to their severityindex as had been assessed by the respondents. Thereafter, the researcher evaluated differences in perceptions of different parties regarding the challenges which cause failure of construction contractors during the execution of construction contracts, using Analysis of Variance combined with multiple comparisons using the Scheffe and Bonferronimethods. The data analysis results showed that out of the thirty identified causes of contractor’sfailure, the top five causes as ranked by consultants are: (1) lack of capital; (2) lack of using project management techniques; (3) adopting unsuitable procurement practices;(4) fraud; and (5) award contracts to lower price. Additionally, the top five causesas ranked by clients are: (1) lack of using project management techniques; (2) lack of capital; (3) adopting unsuitable procurement practices; (4) fraud; and (5) award contracts to lowest price. Also, ranking by the contractors themselves revealed the top five causes of their failure to be: (1) adopting unsuitable procurement practices; (1) lack of capital; (3) inefficient deployment of resources; (4) award contracts to lower price, and lack of controlling equipment cost usage. Finally, it was observed that there is a statistically significant difference between perceptions of different party’s consultants, clients and contractors regarding the managerial, financial, expansion and external causes of contractor’s failure in implementation of their construction projects and also their businesses at the corporate level. From these findings, it was concluded that strategic measures should be taken in order to mitigate the contractor’s failures during execution of construction contracts. From the study findings, it is recommended that the contractors should: