CW-School of Pure and Applied Sciences

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Occurrence and Distribution of high temperature geothermal systems in Kenya
(1993) Ambusso, W.; Onacha, S.A.; Omenda, P.A.
Results of Injection and Tracer Tests in Olkaria East Geothermal Field
(Stanford Universit, 1994-01-18) Ambusso, W.
This paper presents results of a six month Injection and Tracer test done in Olkaria East Geothermal Field The Injection tests show that commencement of injection prior to onset of large drawdown in the reservoir leads to greater sustenance of well production and can reduce well cycling which is a common feature of wells in Olkaria East Field. For cases where injection is started after some drawdown has occurred in the reservoir, injection while leading to improvement of well output can also lead to increase in well cycling which is a non desirable side effect. Tracer tests reveal slow rate of fluid migration (< 5 m/hr). However estimates of the cumulative tracer returns over the period of injection is at least 31 % which is large and reveals the danger of late time thermal drawdown and possible loss of production. It is shown in the discussion that the two sets of results are consistent with a reservoir where high permeability occurs along contact surfaces which act as horizontal "fractures" while the formations between the "fractures" have low permeability. This type of fracture system will lead to channeled flow of injected fluid and therefore greater thermal depletion along the fractures while formations further from the fracture would still be at higher temperature. In an attempt to try and achieve a more uniform thermal depletion in the reservoir, it is proposed that continuous injection be done for short periods ( - 2years) and this be followed by recovery periods of the nearly the same length of time before resumption of injection again.
Ecological management of cereal stem borers in Ethiopia. Integrated Approaches to Higher Maize Productivity in the New Millennium.
(2002) Kairu, E. W.; Degaga, E. G.; Overholt, W. A.
Three lepidopterous stem borers were reported on maize in Ethiopia. Although complete crop loss is evident in some areas, the average yield loss of maize caused by cereal stem borers in Ethiopia can be estimated between 20 and 50%. A resource-poorfarmers produce over 87% of aize, inexpensive, ecologically sound and effective cereal stem borer control methods are indispensable. To this end, surveys and field experiments were conducted in 1999 and 2000. Surveys were conducted in major maize growingareas of eastern, western, southern and northern thiopia. In the surveys, four stel1 borers, 20 species of parasitoids, 14 species of predators and seven entomopathogens were investigated. These natural enemies gave about 18% re<1:uction of cereal stem borers. Of these natural enemies Cotesia flavipes Cameron (Hymenoptera raconidae) alone gave 13% reduction. Intercropping of maize with beans significantly (P
Phytochemical and biological studies of the genus Croton for the development of agrochemical and pharmaceutical products
(2004) Chhabra, S. C.; Thoruwa, C. L.; Thiong'o, G. T.; Akeng'a, T. A.; Wambua, P.; Ndunda, B.; Onyango, I. O.
Over the past two centuries, research into the chemical and biological properties of natural products has yielded novel and more effective therapeutic agents for treatment of many human ailments. There is, therefore, need to focusing on these bioactive metabolites as possible biological controls of agricultural pests.The present study was intended to find some remedial measures to some common problems challenging to man. Seven Kenyan Croton plants, C. alienus Pax, C. dichogamus Pax, C. megalocarpoides Friis Gilbert, C. megalocarpus Hutch., C. menyharthii Pax, C. pseudopulchellus Pax, and C. sylvaticus Hochst. were selected for this study because of their reputation in folklore medicine.Crude extracts of the leaves, stembark and rootbark of these plants were bioassayed for antibacterial, antifungal and nematicidal activities. Based on the preliminary antimicrobial activity test results, four plants were selected for isolation and chemical characterization of compounds from their organic extracts to the chemical state of purity. The pure compounds were also investigated for antimicrobial and nematicidal activities.Liquid vacuum chromatography (LVC), column chromatography (CC) and thin layer chromatography (TLC) were used for isolation and purification of bioactive principles. Spectroscopic measurements like: Ultra violet and infrared radiations (UV IR), mass spectrometer (MS), proton and carbon-13 nuclear magnetic resonance (1HNMR and 13CNMR) were done to facilitate structure elucidation and identification of isolated compounds.Four compounds, lupeol, stigmast-5-en-3-β-ol, crotepoxide and harwickiic acid have been identified from these species which have been found to possess different biological activities.
Subclinical nephrotoxicity caused by smoking and occupational silica exposure among male Kenyan industrial workers
(Moi University, 2007) Mwangi, Daniel M.; Ngeranwa, J.J.N.; McLigeyo, Seth O.; Orinda, George O.; Njagi, E.N.M.
Progress in transformation and regeneration of tropical inbred maize lines in Kenya
(Maize Genetics Cooperative Newsletter, 2008) Mgutu, Allan Jalemba; Anami, E. S.; Hanley-Bowdoin, L.; Rasha, A. O.; Nelissen, H.; Inzé, D.; Van, L. M.; Machuka, J.
Tropical inbred maize lines have a reputation of being difficult to transform, mainly as a result of their inherent limitations associated with resistance to Agrobacterium infection and their recalcitrance to in vitro regeneration. To enhance the capacity for public sector maize transformation, the Plant Transformation Facility at Kenyatta University, Kenya, embarked on a program to improve transformation of diverse tropical inbred maize lines using Agrobacterium tumefaciens. We evaluated both N6 (Frame et al., Plant Physiol. 129:13-22, 2002) versus LS (Negrotto et al., Plant Cell Rep.19:798-803, 2000) media with different hormone regimes and optimized transformation and regeneration protocol for tropical inbred maize lines. Using immature embryos as explants, four Kenyan tropical inbred lines TL21, TL22, TL23 and TL18; two Sudanese inbred lines IL1, IL2 and CIMMYT inbred lines CML 216 and CML 244 have been investigated for their tenability to transformation and regeneration. Transformation frequencies (callus resistant events over total explants) and efficiencies (plantlet regenerating events over total explants) for the recovered events were used to evaluate successful transformation
Animal feed suppliment from avocado residue and other locally available materials
(Kenyatta University, 2009) Ndungu, E.; Gitome, J.; Wanjau, R.; Murungi, J.; Makibia, J.
Kenya's population has been on the increase, and more than 15 million people are poor and live in rural Kenya. Of these, 70% are women, who are particularly vulnerable because they do not have equal access to social economic assets thus widening economic gap and rising poverty levels that erode self-esteem and growth in education, health, food security and employment. Most of the poor people are farmers who, apart from growing crops for subsistence, majority of them also keep livestock as a major source of farm income and manure. Proper feeding of the animals is a critical input in productivity as feeding alone accounts for about 40% of production cost or more depending on the sources of feeds and feed ingredients. The available feeds used by farmers including plant residual and napier grass do not meet all the needs of the cattle kept by most farmers which compromises the productivity of the animals leading to low income for the farmer. In order to improve and empower the small holder farmer, there is need to come up with technologies that. can improve their lives. This project aimed at reducing poverty in Evurore division in Mbeere District, by training the locals to prepare animal feed supplement, using locally available avocados. Avocado is one of the most commonly grown farm products in area and is available throughout the year. The fruit is mainly used as a salad fruit and a source of oil for cosmetic products as well as fuel. The seed and the peels of the avocado fruit have not been fully exploited and are normally thrown away with the garbage. This project was designed to come up with an economical way of producing commercial feed supplement using avocado peels and seed as well as other locally available materials in order to curb the problem of low animal feed resources for livestock. The avocado peels and seeds were analyzed for the levels of essential minerals using atomic absorption spectrometry (AAS) and were found to have substantial amounts of the minerals. The produced animal feed supplement will be used as a source of essential macro and micro nutrients which improve health and productivity of the livestock and consequently that of the farmers. The efficacy of the feed developed will be tested by feeding rats and comparing the results with those of commercially available feed concentrates .
Evolution and diagnostic utility of major surface proteases from trypanosoma vivax, t. Brucei brucei and t. Congolense
(Kenyatta University, 2009) Machuka, Eunice M.; Masiga, Daniel K.; Ouma, Johnson O.; Gichuki, Charity W.
Comparative determination of heavy metals bioaccumulation in bamboo as a phytoremediative process to polluted riverine wetlands
(Kenyatta University, 2009) Orina, B.G.; Anyango, S.O.; Wanjau, R.; Murungi, J.
Nairobi's unplanned settlements have resulted into open drained domestic and industrial waste into tributaries that join the larger Nairobi River at different stages of its development. Polluted water, to is either directly taken up by planted riverine crops or used through irrigation by the residents. Crop production acts as an important commercial venture for the communities living around the basin. Bioaccumulation of heavy metals such as Zn, Cu, Cd and Pb is evident in these crops causing a health risk to urban consumers. Rehabilitating these wetlands with alternative plant species that reinstate purification, not consumed as food with significant commercial value is therefore urgently needed. Bamboo, due to its growth characteristics and heavy metal accumulation tendencies could serve to uptake heavy metals from polluted aquatic ecosystems and also provide an income generating alternative. four species of bamboo; water bamboo, giant bamboo (Dendrocalamus gingateus), yellow and green bamboo (Bambusa spp) and other plants were grown on potted polluted soils from Motoine riverine, and the accumulated levels of Zn, Cu, Pb and Cd were determined at regular intervals. The results showed that bamboo averagely absorbs 243 mg/kg of Zn, 1.3 mg of Cd, 222 mg/kg of Cu and 36 mg/kg of Pb annually in its initial years. Significant correlations were observed between heavy metal concentrations in the soils after the harvests and the bioaccumulations in the bamboo species (P>0.05, DF12, t-test). Very high correlations between reducing soil heavy metal contents and increasing bamboo heavy metal accumulation (r = -0.788).therefore due to the first growth rate and large biomass index, bamboo forms a good plant for bio filtration of these heavy metals. Bamboo production per year is estimated to be between 30-75 tons/ha per year. The total absorption therefore translates to 6.66-16.65 kg of Zn, 7.29- 18.23 kg of Cu, 1.08-2.7kg of Pb, 39-97.5g of Cd per ha/ year. The study recommends building up of bamboo systems along Motoine River in Kibera as a purifying model and substituting them for commercial edible vegetation in slums around wetlands a viable option.
Evaluation of bacille calmeti'e guerin, montanide incomplete seppic and aluminium hydroxide as adjuvants for leishmania vaccine in balb/ c mice
(Kenyatta University, 2009) Muli, J.M.; Macharia, J.C.; Kariuki, T.M.; Gicheru, M. M.
Assessment of the impact of anthropogenic activities on the levels of nitrates and nitrites in Mathare-Gitathuru drainage basin
(Kenyatta University, 2009) Nguyo, J.M.; Wanjau, R.N.; Murungi, J.I.; Moko, F.N.
Use of a non-mist propagation system to vegetatively propagate 12 E. grandis X E. Camadulensis hybrid clones
(Kenyatta University, 2009) Mwaniki, F.N.; Muluvi, G. M.; Gichuki, C.; Oeba, V.; Kanyi, B.
Effect of larval food plants and seasons on the quality of the African wild silkmoth, gonometa postica walker (lepidoptera: lasiocampidae) cocoons
(Kenyatta University, 2009) Fening, K. O.; Kioko, E. N.; Raina, S. K.; Mueke, J. M.
Wild silkmoth farming offers an economic incentive for forest-adjacent communities to fully participate in forest conservation initiatives. Gonometa postica Walker is known to produce high-quality silk. It is being utilised for commercial wild silk production by the forest-adjacent communities in Mwingi District in Kenya. The developmental time of G. postica larvae and cocoons quality were studied in the Imba and Mumoni woodlands of Mwingi during the long and short rainy seasons of 2006 and 2007. Acacia elatior Brenan, Acacia tortilis (Forssk.) and Acacia nilotica (L.) Del were used as larval host plants. Larvae were reared in semi-captivity by using net sleeves attached to the branches of the host plants. Also, cocoons from the wild population were sampled from the host plants to evaluate their quality. The weight and size of cocoons were used as the determinant of their quality. Larval developmental period and cocoons quality differed according to host plants, seasons and sites, for those reared in semi-captivity. However, cocoons quality from the wild habitat varied with seasons and sites but not with host plants. Larvae reared on A. elatior had the shortest developmental period and highest cocoons quality than those raised on A. tortilis and A. nilotica. Thus, A. elatior is recommended as the most suitable host plant for the semi-captive rearing of G. postica larvae. This will help augment the natural population of the silkmoth and to ensure the sustainable harvesting of the cocoons.
Water quality status and the planktonic constituents of undrainable water reservoirs in the semi-arid Naromoru area of central Kenya
(Kenyatta University, 2009) Mwangi, Benson M.; Ndiwa, Titus; Kairu, E. W.
Experimental analysis and modeling of the< i> IV characteristics of photovoltaic solar cells under solar spectrum spot illumination
(Elsevier, 2009-12) Munji, M. K.; van Dyk, E.E.; Vorster, F.J.
In this paper, some models that have been put forward to explain the characteristics of a photovoltaic solar cell device under solar spot-illumination are investigated. In the experimental procedure, small areas of the cell were selected and illuminated at different solar intensities. The solar cell open circuit voltage (Voc) and short circuit current (Isc) obtained at different illumination intensities was used to determine the solar cell ideality factor. By varying the illuminated area on the solar cell, changes in the ideality factor were studied. The ideality factor obtained increases with decreasing illumination surface ratio. The photo-generated current at the illuminated part of the cell is assumed to act as a dc source that injects charge carriers into the p–n junction of the whole solar cell while the dark region of the solar cell operates in a low space charge recombination regime with small diffusion currents. From this analysis, a different model of a spot illuminated cell that uses the variation of ideality factor with the illuminated area is proposed.
Prospecting for bacillus thuringiensis for the control of prostephanus truncatus (horn) and sitophilus zeamais motschulsky
(2010) Machuka, Jesse; Likhayo, P.; Nang’ayo, F.; Maniania, N.
Three hundred twenty nine samples from different parts of Kenya which had not previously been treated with bio-pesticide were collected for Bacillus thuringiensis isolation. The δ-endotoxin crystals were isolated from nutrient broth culture by medium speed centrifugation. From the colony samples examined, 77.1% (236) were non crystal forming Bacillus, 16% (49) Bacillus thuringiensis and 6.9% (21) Bacillus sphaericus. The B. thuringiensis isolates were evaluated for insecticidal activity against Prostephanus truncates and Sitophilus zeamais using artificial seeds incorporating spore – crystal toxins at the rate of 4% w/w. Twenty five unsexed 2-week-old P. truncates and S. zeamais adults were separately fed for 14 days with ten seedsof each isolate contained in ventilated glass tubes. Seeds prepared with sterile distilled water only served as controls. None of the isolates showed satisfactory control of the two coleopteran species. The results demonstrate minimal prospects of finding more potent Bacillus thuringiensis from local sources.
Regeneration and transformation potential of elite Kenyan highland maize inbred lines
(2010) Machuka, Jesse; Taracha, C.; Nangayo, F.; Ombakho, G.
Agrobacterium-mediated transformation of tropical maize has been manipulated in only a limited number of genotypes, because a majority of maize germplasm isrecalcitrant toin vitroresponse. Establishment of a highly efficiency and widely used tissue culture system for maize will accelerate the application of transformation technology in breeding programs, and the study of the functions of maize specific genes. Out of the three media evaluated, it was established that two media could guarantee the production and proliferation of a large number of embyogenic calli with high regeneration capacityfrom immature zygotic embryos representing different maize germplasm. The results suggest that the evaluated tissue system will be widely applicable for the tissue culture of Elite Kenyan Highland inbred maize lines
Determination of insecticidal activity of Kenyan Bt isolates against the spotted stem borer, chilo partellus
(2010) Nyambaka, H. N.; Kimani, G.; Gichuki, S.; Amata, R.; Okomo, M.; Kasina, M.
The delta – endotoxin crystals containing insecticidal Cryproteins were isolated from 20 unidentified local Bacillus thuringiensis Berliner (Bt)isolates and a reference isolate Bt aizawai(Bta) using froth floatation and low speed centrifugation at KARI Biotechnology laboratories, NARL. The total protein was quantified using the Bradford assay method and protein yield from the nutrientbroths was estimated at 3.11 mg/ml ±0.938 mg/ml of nutrient broth culture with a purity level of 54.8% ±15.3% of the protein pellet. Leaf – dip bioassay was used to determine the efficacy of the isolates against Chilo Partellus (Swinhoe), a well-established and invasive stem borer in Kenya. Among the isolates, Bt44 and Bt48 had the most potent endotoxin crystals to 1stinstar C. partelluslarvae. In addition, the efficacy of these two isolates was not statistically different (P>0.05) from that of Btabased on LT50 values. The findings show that these two locally available unidentified Bt isolates could be used in management of C. partellusand their characterisation (Cryprotein) could aid in their utilization.
Preferred Banana Varieties and their Seed Systems in Eastern and Central provinces of Kenya
(Ruforum, 2010) Mwangi, M.; Kasyoka, M.R.; Mbaka, J.; Kori, N.; Gitonga, N.; Muasya, R.; Adipala, E.; Tusiime, G.; Majaliwa, J.G.M.
Banana is an important crop for food security in Kenya. Its production has been hindered by scarcity of seedlings and pests, among other factors. A recent survey in eastern and central Kenya showed that desert varieties are prefered due to market demand. Natural regeneration is also preferred by most farmers (>85%) but it is inefficient and a source of pests and diseases to new plantations. On the other hand, adoption of tissue culture has been hindered by high cost of seedlings. Farmers need to be educated on shortcomings of natural regeneration and affordable seedling delivery system implemented. Macropropagation supported by an efficient delivery system is proposed to boost banana production in Kenya.
Effect of bacillus thuringiensis (bt)–cotton protein endotoxins (cryiac and cry2ab2) on below ground fauna diversity with reference to entomopathogenic nematodes
(2010) Mbugi, J.P.; Njinju, S.M.; Waturu, C.N.
This study was conducted with the aim of determining the impact of genetically modified (GM) cotton on the diversity of below ground fauna. The entomopathogenic nematode, Steinernema karii infectivity to the larvae of the wax moth was also used to determine the effect of Bacillus thuringensis-cotton protein endotoxin on below ground biodiversity. Soils from theconfined field trial area had a diverse fauna that included Hemiptera, Hymenoptera, Coleoptera, spiders, wireworms and chaffer grabs. Cotton containing Bt series, non Bt cotton and kenaf were grown in pots under confined conditions and uprooted at flowering stage. Soils from the rhizosphere (soils that adhered to the roots) were tested for the presence of Bt endotoxin using the Quick Stix Comb strip method and were found to be positive for the endotoxin even within non Bt treatments. Those soils werethen inoculated with S.karii and fifth instar larvae of the wax moth, Galleria mellonella in the laboratory. Cadavers of Galleria larvae were recovered from the soils over a period of 10 days and dissected to confirm the cause of mortality. Data was transformed using SQRX + 1, subjected to Analysis Of Variance (ANOVA) and means separated using LSD. Results from the study showed that there were no significant differences between treatments. Galleria larva mortality due to S. karii infections were 64%, 63%, 61% and 50% for HART89M, sterilized soil, Bt cotton and Isoline treatments respectively. A number of false positives were recorded during the experiment for the Bt toxin implying that further refinement of the Quick Stix comb strip technique is required.

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