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Effect of Irrigation, Nitrogen and Zinc on Nitrogen and Zinc Content and Uptake in Late Sown Wheat Biomass
(Egerton University, 2006-01-01) Kibe, A.M; Titus, S; Singh, S
Continuous rice-wheat cropping systems that are heavily dependent on irrigation water, has become a matter of great concern in South Asian countries, particularly in India. This has lead to nutrient and ground water depletion, as well as soil degradation due to formation of saline/sodic soils. Due to this, a field experiment was conducted on a sandy loam soil in New Delhi, to determine nutrient content and uptake by a late-sown-wheat (HD 2285) under varying water, nitrogen and zinc levels. Treatments comprised of four levels of irrigation in main plots and a combination of three N and two Zn levels in the sub plots of a split plot design, replicated thrice. Nitrogen content in the above ground biomass declined with progression in wheat growth, from a maximum of 4.0% at 30 days after sowing (DAS) to a minimum of 1.1% at 90 DAS. This was however inversely associated with an increase in N uptake from a minimum of 12.4 kg/ha to a maximum of 99 kg/ha over the same period. Nitrogen content in biomass at 90 DAS, increased significantly (P≤0.05) with increase in irrigation levels, attaining a maximum of 1.393%, under the two irrigation treatment (I2), applied at crown root initiation and flowering stages of wheat. Highest grain N (1.7%) was obtained with I2 and I3 (four irrigation, given at CRI, jointing, flowering and milk stages) treatments. N uptake ranged from 54.7 to 115.8 kg/ha N under the (I0) and (I3) treatments, respectively. Application of 100 kg/ha N significantly increased N uptake in the aboveground biomass at the 60 and 90 DAS growth stages. Grain N consisted of 63 to 69% of total N uptake in wheat. Application of I3 resulted in the highest straw Zn content (44.3 and 40.7 mg/ha) and zinc uptake (177.6 and 159.4 g/ha) was with I3 in seasons I and II, respectively. Zinc application at the rate of 5 kg/ha significantly increased zinc uptake in the grains (82.04 and 72.51 g/ha) over the no zinc application treatment (76.03 and 66.50 g/ha) in both seasons, respectively. Where input and water are limiting (e.g. ≤ 48 kg/ha N and 186 mm water), mean grain yields of 2.29 tons/ha can be obtained. When water and N are adequate (i.e. 110 kg/ha N and 250–330 mm water irrigated 2 to 4 times), 3.96 tons/ha of wheat grain can be harvested.
Population Dynamics of Waterbirds in Wastewater Lagoons in Njoro, Kenya
(Egerton University, 2006-01-01) Kipkemboi, J.; M’Erimba, C; Mathooko, J. M; Mokaya, S
Waterbirds were studied in a series of three wastewater lagoons located at Egerton University, Njoro Division, Kenya, to elucidate their spatio-temporal population dynamics. The sacred ibis and the yellow-billed ducks were most abundant in the lagoon with raw unprocessed sewage (WLI). The population of yellow-billed ducks in WLI differed significantly from the populations in the middle lagoon (WLII) and in the last lagoon (WLIII) before the ‘processed water’ was discharged into the Njoro River. Post-hoc analysis using Bonferroni multiple range test ( = 0.05) indicated that WLI had the highest populations of yellow-billed ducks, sacred ibis and the Egyptian geese. The group sizes of the Egyptian geese in WLI were between 6-10 individuals. The diurnal distribution of the bird populations in the three lagoons did not define distinct patterns although the population of red-billed teals in WLI showed a peak increase at around 1200 h. The observed fluctuations of the populations within very short temporal periods indicated that the birds were not flying far from their habitat. They were returning to the lagoons within 2-4 hours. The highest number of birds was counted between 1200 and 1400 h, 0800 and 1000 h and, 1200 and 1400 h, in WLI, II and III, respectively. Chironomus gr. plumosus (Chironomidae) dominated the macroinvertebrate assemblages in the wastewater and could be food for the waterbirds. Total body lengths of the chironomids in all the three lagoons were similar. The size structures portrayed by the invertebrates in the three lagoons raised questions on food selectivity by the birds and/or survival strategies by the invertebrates themselves. The current data indicate that bird populations could be used to determine roughly the health of wastewater lagoons. The value of wastewater lagoons as small-sized bird sites needs full recognition.
Effect of Heterologous Challenge on the Survival of Sheep Immunzed with Inactivated Elementary Bodies and Recombinant Antigens of Cowdria ruminantium
(Egerton University, 2006-01-01) Kibor, A. C; Sumption, J. K; Paxton, E. A
Immunization of sheep with inactivated elementary bodies (IEB’s) confers protection against homologous and heterologous challenge among certain stocks of C. ruminantium. Cros-protection between different stocks of C. ruminantium using recombinant antigens is being reported in this study. Immunization of sheep with 250µg IEB’s of the Gardel stock protected 5 sheep out of 8 (64.5%) against a virulent Kenyan isolate the Kathiani. There was no advantage in terms of protection against virulent challenge when 35µg of recombinant Major Antigen Protein 1 (MAP1=32 kilodalton protein) or MAP2 (21 kilodalton protein) of C. ruminantium were combined with 100µg of IEB’s. Immunization with recombinant MAP1 antigen did not protect sheep against heterologus challenge, however immunization with 35µg of recombinant MAP2 antigen protected 7 out of 8 (87.5%) sheep immunized with this antigen. This result was surprising and further immunization experiments are required to determine the potential of this recombinant for vaccine production in the future
Development and Biotechnology of Pleurotus Mushroom Cultivation
(Egerton University, 2006-01-11) Khare, K. B; Achwanya, O. S; Mutuku, J. M; Gathuru, E. M; Ombiri, J
The increasing population and the decreasing land size for crop cultivation throughout the world poses a serious problem to sufficient food production. The cultivation of Pleurotus mushrooms requires less elaborate technologies. The Pleurotus mushroom can adapt easily in rural areas since it can utilize farm wastes. The cultivation of Pleurotus mushroom could be an avenue to solving problems associated with deficiency of proteins, minerals and vitamins. During the last two decades, cultivation of Pleurotus mushrooms has become popular worldwide because of their desired attributes. These attributes include: the wide choice of species for cultivation under different climatic conditions, ability to grow on a variety of agricultural and industrial wastes, and their richness in culinary and nutritional values. In this paper, the importance, development and various biotechnological methods in respect to the cultivation of Pleurotus mushrooms are discussed. A simple method used by the authors for cultivation of Pleurotus florida on locally available substrate, rhodes grass (Chloris gayana L.) is also provided.
Computational Pool-Testing Strategy
(Egerton Journal of Science and technology, 2011-01-10) Mwangi, Jesse W; Nyongesa, L K; Tamba, L C
Pooling sample for the purpose of testing has a long history dating back to the Second World War with its first application being screening of pooled urine samples for the presence of syphilis. Recently, pooling has been used in epidemiological studies for screening of human immunodeficiency virus HIV/AIDS antibody to help curb the spread of the virus. Pooling reduces the cost but also – and more importantly – offers a feasible way to lower the misclassifications associated with labeling samples when imperfect tests are used in inspection. Computer intensive pool-testing strategy is discussed in this study with a view to digitalizing the procedure. Moments of the number of tests as in the traditional pool-testing strategy have been digitized via MATLAB code and the same has been done for the case of misclassifications associated with this strategy. Moments are used in the computation of the cost or efficiency associated with pool-testing procedure. The digitalization provides insight into the merits and demerits of the pooltesting procedure supported by empirical evidence
Modeling and Analysis of AC-DC Converter PID Controller Optimized with Pattern Search Algorithm
(Egerton Journal of Science and technology, 2011-01-10) M. M, Kanai,; J. N., Nderu; P.K., Hinga,
The paper presents a tuning methodology for the parameters of a PID controller in a three phase Pulse Width Modulation (PWM) Three-Level ACDC converter system, often referred as Improved Power Quality Converters (IPQC). A PID Controller is a generic control loop feedback mechanism (controller) widely used in industrial control systems. A PID controller calculates an "error" value as the difference between a measured process variable and a desired point. Three-phase Three-level AC-DC converters have been developed to a matured level with improved power quality in terms of power-factor correction, reduced total harmonic distortion at input ac mains, and regulated dc output. However, for best performance, the PID parameters used in the calculation must be tuned according to the nature of the system – while the design is generic, the parameters depend on the specific system. The parameters of converter, which vary with the operating conditions of the system, are adapted in order to maintain desirable response for output voltage and power factor. A Pattern Search Optimization (PSO) algorithm is employed in order to obtain the controller parameters assuring improved response at selected load. The Three-level AC-DC converter PIDPSO controller is modeled in MATLAB environment. The response of the developed controllers is compared to that of the controller whose parameters are tuned using the well-known Ziegler-Nichols method. The developed method is more proficient in improving the controller loop settling time, the rising time and overshoot and hence the disturbances do not affect the performances of Three-Level AC-DC converter.
Land and Soil Resources and their Management for Sustainable Agricultural Production in Kenya: Current Position and Future Challenges
(Egerton Journal of Science and technology, 2011-01-10) Sigunga, D. O.; Wandahwa, P. J.
Land and soil make up the cardinal resource-base in any agricultural production system and, hence, their proper management is vital for sustainable agricultural production. A study was conducted to evaluate the availability and accessibility as well as constraints to utilization of land and soil resources for sustainable agricultural production in Kenya. The study covered 33 districts drawn from 6 out of the 8 administrative provinces in the country. The selected districts were drawn from agriculturally active provinces. The methodology used in data gathering included collection of information from secondary sources, use of questionnaires, field visits and personal interviews. The country has an area of 583,000 km2, out of which land and water occupy 571,770 and 11,230 km2, respectively. About 33% and 67% of Kenya’s land mass are designated as available agricultural land and arid and semiarid land, respectively. Less than 40% of the available agricultural land is utilized. Only 5% of the country’s drainage potential is developed. Besides, most of the semiarid land is of high potential for agricultural production provided irrigation is applied. The country’s irrigation potential is estimated at 54,000 ha out of which 20% is developed. More land may be reclaimed for agricultural production from the semi-arid land by applying irrigation. Agricultural land availability is, therefore, not limiting to agricultural production. Skewed land ownership that leaves most of the land in the hands of few people is a factor that undermines access to, and development of, the land. Erosion risk and soil shallowness are important constraints. Suitable land/soil conservation measures targeting all forms of soil degradation processes in relation to agricultural systems in given agro-ecological zones need to be developed if the land/soil resources of the country are to be utilized for sustainable agricultural production.
Comparative Ecological Analysis of Fish Parasitofauna in a Hub- Plot Aquaculture System: Implications for Aquaculture in Kenya
(Egerton Journal of Science and technology, 2011-01-10) E., Otachi; E., Wathuta; A., Magana; M. L., Fioravanti; D., Florio; R., Konecny
Aquaculture is an important source of food globally. The Kenya Government through the economic stimulus package (ESP) in a supplementary budget of 2009/2010, allocated Kshs.1.12 Billion for the establishment of 200 fish ponds in each of the 140 potential constituencies in an effort aimed at enhancing food security by increasing fish production in the country. Fish diseases and parasitic infections have been and still remain peripherally recognized as one of the detrimental and limiting factors in the development of the aquaculture sector. This research was set to study the diffusion and dispersion of parasites in Oreochromis niloticus fish cultured in a typical hub and plot system in an integrated cage fish culture in Kenya. The system was based on a hub (source of seed) from Sagana Aquaculture Centre and a plot (farm) in Machakos, Kwa- Ngeki reservoir. Specific objectives were to detect and identify parasites, determine their prevalence, mean intensity and abundance; and compare the distribution of major parasites in the hub and plot. Using routine necropsy and parasitological examination procedures a total of 370 Oreochromis niloticus fish (57 caged and 313 from open ponds) were examined for the presence of parasites. Ecological community diversities and similarity indices were used to compare the parasitofaunal assemblages between the hub and the plot. Data on prevalence, mean intensities, abundance, diversities and similarity indices on distribution of parasites as well as their implications in this rapidly growing sector of the economy are presented in this paper.
Estimation of Growth Parameters of Indigenous Chicken Populations Intensively Reared in Kenya
(Egerton Journal of Science and technology, 2011-01-10) Kahi, Alexander; Bebe, B O; Ngeno, K
This study compared body weights of indigenous chicken (IC) ecotypes from 0 to 34 weeks of age and modeled the growth curves to estimate the associated parameters and their relationship using four growth models, namely: Von-Bertalanffy, Gompertz, Logistic, and Brody. A total of 17,748 age-weight data collected biweekly on 522 birds belonging to five ecotypes, namely, Bomet (BE), Bondo (OE), Kakamega (KE), Narok (NE) and West Pokot (WE) were evaluated. Over the growth period, OE was the heaviest from week 2. However, from week 12 onwards, there were no significant differences in body weight between the ecotypes. The fitted parameters for growth demonstrate ecotype differences (P<0.05) in the asymptotic weights (A), maturity index (k) and scaling parameters (b) in all the models. However, A were not different (P>0.05) among BE, NE and WE. The correlations between A and k were negative for all ecotypes in all models, and ranged from -0.63 to -0.99. The age at constant degree of maturity in all the models differed (P<0.05) among the ecotypes. Estimates from the Brody model indicated that IC attained maturity when older. The study revealed differences in growth curve parameters and patterns among the ecotypes, which indicate genetic influences. Such differences among the ecotypes give the chance to choose the best parental lines for practical IC breeding and development of commercial stock through selection and/ or crossbreeding
Spatial and Temporal Variations of Zooplankton in Relation to Some Environmental Factors in Lake Baringo, Kenya
(Egerton Journal of Science and technology, 2011-01-10) Omondi, R.; Yasindi, A. W.; Magana, A.
The zooplankton community of Lake Baringo, a shallow and turbid lake in the eastern arm of the Great Rift Valley in Kenya, was studied between April 2008 and November 2009. This study focused on the spatial and temporal distribution, composition and abundance of zooplankton in the lake. Physicochemical variables measurements and triplicate zooplankton samples were taken monthly from five stations. The zooplankton community comprised 31 species. Only two Copepod species, Thermocyclops consimilis and Thermodiaptomus galebi were recorded in the orders Cyclopoida and Calanoida respectively. Cladocera was represented by 8 species, with Diaphanosoma excisum being the most common in all sampling stations. Rotifera, with five families, had a total of 21 species. Spatially, species diversity ranged from 0.649 in C2 to 0.695 in C1 while temporally these were 0.36 to 0.87 in September 2009 and June 2008 respectively. The mean zooplankton abundance per station varied from 27.46±4.16 individuals l-1 in December, 2008 to 120.13±17.50 individuals l-1 in November 2009. Among sampling sites, C3 had the highest abundance (79.09±7.95 individuals l-1) and the lowest abundance was recorded at C1 (56.37±6.58 individuals l-1). There was significant difference between the sampling stations (P<0.001) and among the sampling months (P<0.001). A number of environmental parameters were correlated with the abundance of different species of zooplankton.
Effects of Macrobends on the Attenuation of Optical Signals in Multi-Mode Graded Index 62.5/125 μm Cable at 850 nm Wavelength
(Egerton University, 2012-10) Chombah, . J.M.; Gwaro, J.O.; Nyaanga, .D.M; Kirui, M.S.K
In fibre optic transmissions, macrobend is a large visible bend in the optical fiber that can cause attenuation, a reduction of optical power in the glass. A relatively large- radius bend in an optical fibre may results to the degradation of the optical signal. In this paper, different magnitudes of circular macrobends in graded index 62.5/125 cable at 850 nm wavelength were used to determine the effect of macrobends on attenuation of signals. A special bending jig was used to produce circular bends ranging from 3mm to 200mm. The insertion method was used while attenuation (signal power loss) was measured in decibels (dB). Statistical analysis software (SAS) at a significant level of 5 per cent (and least significantdifference (LSD) ranking method were used for data analysis. The findings showed that large magnitude of macrobend radii (above 40.0mm) resulted in low attenuation (about 9.0 dB) of signals, while small size bend radii (about 3.0 mm) produced very high (about 40.0 dB ) ofsignal losses. The research findings indicate that macrobends have significant effects on the attenuation of optical signals.
Reproduction Inhibition Effects of Neem Products on the Larger Grain Borer (Prostephanus truncatus)(HORN) in Stored Maize Grains
(Egerton University, 2012-10) Ogemah, .V.; Reichmuth, .C.; Buttner, . C.; Ayiecho, .P.O; Keya, .N.C.O.
The larger grain borer (LGB), Prostephanus truncatus (HORN), has become one of the most important insect pest of stored maize in tropical Africa where it was introduced in the early 1980s. It has the major effect of seriously damaging dry stored maize grains and so increasing post-harvest losses and contributing towards food shortage in this region. Losses of up to 85% by weight and 100% by food value have been reported. A study was conducted to investigate the effects of two neem products, neem oil and NeemAzal® powder on egg laying, hatching, larval development and adult emergence of the pest on shelled maize. Treatment of the grains with sub-lethal dosages resulted in 76.3% and 0.6% reduction in egg laying by neem oil and NeemAzal®, respectively. No adults emerged from samples treated with 0.3 and 0.6% w/w NeemAzal® and ca 2% v/w of neem oil. Generally, neem oil reduced the progeny population more than the adult population, the contrast of which was true for NeemAzal®. When the grains were treated after oviposition, no progeny emerged in neem oil samples while 4.4 and 20 larvae, 3.4 and 27.8 live adults and 17.6 and 1.4 dead adults were observed in NeemAzal® and control samples, respectively. The grain weight loss recorded was significantly lower for neem oil than for NeemAzal®. The two products have different effects on LGB, neem oil being effective in controlling early stages while NeemAzal® is more effective in controlling the adults. It can therefore be concluded that the effect of the neem products used in this study on LGB depended more on the formulation than on the content or dosage of azadirachtin used. The results of this study will help refocus research on the control of LGB towards design of appropriate formulations of neem products, which will make them useful in the control of the management of LGB by small scale, resource poor farmers in Africa.
Post-treatment Prevalence of Schistosomiasis and Geohelminthic Infections in Children and Adults Living along Lake Victoria, Kenya
(Egerton University, 2012-10) Njiri, O. A.; Odhiambo, R. A. O; Shivairo, R. S.; Karanja, D. M. S
Schistosomiasis and geohelminthic infections are major public health problems in developing countries and exert a heavy burden on morbidity when they occur singly or concurrently. Chemotherapeutic approach has been adopted in many endemic areas, using praziquantel and albendazole, based on World Health Organization (WHO) recommendations for control. The need for cost-effectiveness considerations in control strategies requires that greater emphasis be placed on further research to understand the factors that determine their occurrence and response to chemotherapy when they occur singly or concurrently. Towards this, a longitudinal survey in Kisumu and Siaya counties, Kenya, was conducted to assess the post-treatment prevalence of Schistosoma mansoni, Trichuris trichiura, Ascaris lumbricoidesand hookworms in school children (9–12 years) and adults over a 9-month period (September 2008 – May 2009). Adults were followed up monthly, while children were followed up every two months. Baseline prevalence of schistosomiasis was 52.0% + 2.5% in adults, and 38.5% + 1.8% in children while that of geohelminthiasis was 22.5% + 3.9% and 55.6% + 4.1% in adults and school children respectively. The difference in prevalence between the adults and children for both schistosomiasis and geohelmithes was not significant (P=0.9302), After 9 and 5 treatments in adults and children respectively, there was reduction in prevalence of schistosomiasis to 28.9% +2.3% and 24.0% + 3.1% in adults and children respectively, while in geohelminthiasis prevalence reduced to 4.3% + 1.5% in adults and 27.0% +2.5% in school children. These difference in prevalence among adults and children was not significant (P=0.8717). This study shows the differential occurrence of schistosomiasis and geohelmiths in children and adults. It also shows that frequent and consistent treatment decreases the prevalence of Post-treatment Prevalence of Helminth Infections along Lake Victoria 133 Egerton J. Sci. & Technol. Volume 12: 132-145ISSN No. 2073 - 8277 helminths in endemic areas and is effective both in adults and children. There’s however need for further studies to determine the most cost-effective strategies for mass drug administration, that will impact morbidity caused by helminths to sustainable levels in vulnerable groups.
Epidemiological Factors Determining Clinical Malaria in the Highlands of Western Kenya: Case Study of Iguhu Location
(Egerton University, 2012-10) Essendi, M.W.; Shivairo, R.S.; Muleke, C.I.; Yaw, Afrane; Odhiambo, R.O.
This paper reports findings on the prevailing “epidemiological factors that determine occurrence of clinical malaria in the highlands of western Kenya, a case study of Iguhu location.In this study, the risk factors associated with clinical malaria in western Kenya highlands were evaluated. A simple household survey of existing clinical malaria cases and their age-matched cohorts was undertaken to collect information on the potential exposure factors and prevailing socio-economic status. Mosquito samples were harvested from participants’ houses for identification and cataloging. The differences in parasite and vector populations in clinical malaria cases and controls were determined using the “t-test”. The results showed that sex, age, household population, education level and occupation status of the household head were not significant determinants for clinical malaria in the area of study. These was in contrast, to families whose spouses were employed and educated to tertiary level that exhibited lower infections rates since they had used insecticide treated nets (ITNs) prophylaxis and mosquito prevention measures. These significantly reduced the disease incidence suggesting that socio economic factors played a role in the ailment control. These findings show that clinical malaria incidence in western Kenya highlands is likely to be influenced by both biotic and abiotic factors including parasite and vector densities suggesting that any successful eradication program should be directed towards prevailing local conditions in a given area.
Influence of Maternal High Protein Intake on Daily Energy Expenditure and Lactation Performance in the Laboratory Mouse
(Egerton University, 2012-10) Kagya-Agyemang, J. K; Król, E.; Speakman, J. R.
Laboratory mouse (strain MF1) was used as a model to investigate the effects of high protein intake on daily energy expenditure and lactation performance. The specific dynamic action (SDA) for high protein (HP: 60% energy as protein) and high carbohydrate (HC: 70% energy as carbohydrate) diets was measured using open-flow respirometry at 9.4% and 6.1%, respectively. The same two diets were fed ad libitum to mice during lactation. Mice fed on HP and HC diets at 21 ºC reached an asymptote in their daily food intake at 12.29±0.2 g day-1 and 16.57±0.2 g day-1, respectively between days 12-17 of lactation. HP-fed mice had a significantly higher daily energy expenditure (DEE) measured by doubly labelled water (133.4±4.8 kJ day-1) and higher water turnover (41.1±6.2 g day-1) than HC-fed mice (DEE: 102.1 ±14.2 kJ day-1 and water turnover: 26.7±6.5 g day-1) but the energy they exported as milk was significantly lower (84.2±31.4 kJ day-1) than that of HC-fed mice (164.6±30.5 kJ day-1) and therefore resulted in poor growth rate of theiroffspring.The urea production of HP-fed mice from their daily protein intake of 7.1 g was estimated at 1994 mg which required 10.2 ml of water per day to be cleared. The mice increased their urine production by 14.4 ml probably to eliminate this urea.In conclusion, the MF1 mice fed HP diet at 21 ºC and the HC-fed mice reached an asymptote in their daily food intake at 12.29 g day-1 and 16.57 g day-1 respectively, between days 12-17 of lactation. HP diet had negative effects on lactation performance at 21 ºC when compared with the HC diet. The negative effects of the HP diet were due to the higher DEE which resulted from the heat production consequent of digestion and milk production by the HP-fed mice. Therefore, the higher DEE greatly reduced the energy available for milk production.This probably explains the reduction in growth of the pups/offspring from the HP-fed mothers because they did not get sufficient energy for growth.
Line-of-Sight-Polarized Wide-Band Mimo Measurements at 2-5 GHz
(Egerton University, 2012-10) Muhehe, D. J.; Muia, M. L.; Ogola, .W.
A short- range line of sight (LOS) multiple-input multiple-output (MIMO) channel transfer function was measured for a 4x4 system between 2.0 and 5.0 GHz. Measurements were made for a fixed antenna spacing of 2λ for all the four antenna polarizations in an indoor environment. Capacity and spatial correlation were investigated and the maximum mean capacity loss of 7.18% was realized when the orientation of the receiving and the transmitting antenna arrays were transformed from co-polar to cross-polar configuration. Furthermore, a validity test was conducted and the empirical distribution was found to be the same and within the theoretical values.
Rescheduling Lengthy Downloads on Bottleneck Links
(Egerton University, 2012-10) Odongo, . Y. G.; Rai, . A. I.
TCP’s ability to share bottleneck bandwidth fairly and efficiently dwindles when faced with an increase in the number of competing flows. Indeed studies have shown that long TCP flows consume more than 90% of the available bandwidth, with short flows consuming a very small portion. It is also known that out of these, a very small percentage of the largest flows carry the majority of the bytes. The utilization pattern of bottleneck links exacerbates this situation. During the daytime (peak period), the network utilization is characteristically high whereas at night (off-peak period), the link is virtually idle. At peak periods, TCP’s congestion control mechanisms highly favour long-lived flows at the expense of their short-lived counterparts. We discuss the design and implementation of a flow rescheduling tool. The tool identifies, blocks and reschedules long flows to reconnect during the off-peak period. Network bottlenecks are a commonplace phenomenon in many IP networks just as much as they are unavoidable. TCP’s ability to share bottleneck bandwidth fairly and efficiently dwindles when faced with an increase in the number of competing flows. Indeed recent studies have shown that long TCP flows consume more than 90% of the available bandwidth, with short flows consuming a very small portion. It has also been realized that out of these, a very small percentage of the largest flows carry the majority of the bytes. The utilization pattern of bottleneck links does not make matters any better. During the day, the utilization pattern is characteristically high whereas at night, the link is virtually idle. We refer to these times as the peak and off-peak periods respectively. At peak time, TCP’s congestion control mechanisms highly favor long-lived flows at the expense of their short-lived counterparts. This work discusses the design and implementation of a flow rescheduling tool, specifically illustrating the techniques used to achieve accuracy and robustness. The tool works by identifying and rescheduling long flows to reconnect during the off-peak period, when link utilization is very low. We present validation results for the tool which demonstrate its reliability in the face of actual Internet conditions.
Effects of Surface Tension over a Flow Past a Flat Plate
(Egerton University, 2012-10) Gathia, P.W.; Lonyangapuo, . P.
We consider a free surface flow past a flat plate. We consider relations between the results of Anderson and Vanden-Broeck (1996) and those of Osborne and Stump (2000), and present new solutions. There is need to know the number of parameters needed to fix solutions uniquely. We show here that there is a three parameter family of solutions when the fluid is of finite depth. These solutions are characterised by a train of waves in the downstream region and by a discontinuity in slope at the separation point. The family includes a two parameter sub-family for which the free surface leaves the plate tangentially. It is shown that this sub-family reduces to the linear solutions of Osborne and Stump (2000) when the depth of submergence of the plate is small. Also, the three parameter family reduces to the one parameter family of Anderson and Vanden-Broeck (1996) as the depth of the water tends to infinity. Finally, fully nonlinear solutions with large capillary waves are presented.
Determination of Triumfetta tomentosa B. Growth Parameters and Fibre Properties in Kenya
(Egerton University, 2012-10) Kinuthia, . N. L.; Mathooko, . M. J.; Kariuki, T. S.; Mucheke, W.
Triumfettatomentosa B. (Fam. Tiliaceae) is an indigenous perennial shrub growing naturally in moist habitats. It is a multipurpose plant traditionally used by many communities in Kenya as a source of fodder, fiber for baskets and ropes and wood for winnowing trays. However, as population increases, the suitable habitat for the shrub is being converted into agricultural and settlement sites making T. tomentosa an endangered species. Kenya needs a cheap source of vegetable fiber in order to revive its textile industries and make industrialization a reality by the year 2030. Currently Kenya spends about Ksh 20M in imported vegetable fibres. The aim of this study was to investigate methods of cultivating T. tomentosa and processing its fibres. Seeds and cuttings were collected from Mt. Kenya and Karura forests. These were raised in nurseries at Muguga (Kenya Forestry Research Institute - KEFRI). The seedlings were transplanted after attaining about 25-40 cm in height. Three experimental sites including Embu, Meru and Muguga were used for cultivation of T.tomentosa. Random Block Design method was used at spacing of 30 cm X 30 cm and 45 cm X 45 cm in 3 replicates for each plant material. Growth in height and diameter at breath (dbh) was measured after every month until about 50% of all the plants had formed flowers. Others were subjected to retting at Egerton University to release fibres. Fiber properties were tested at Kenya Bureau of Standards (KEBS) in Nairobi, Kenya. Descriptive statistics, Chi-square test of independence and Mann-Whitney U test of significance models were used. Cuttings from Karura had a higher shooting percentage (70%) than those from Mt. Kenya forest (40%). Plants from Embu plot gave the highest fiber yield among the three plots, while tenacity tests showed significant difference between fibres from cuttings and those from seeds. The results showed that it was easier to cultivate T. tomentosa from cuttings. Its fibres were close to those of Jute in tenacity and therefore good for making sacks, ropes and mats.
Determination of the Bending Strength and Hardness Values of Sisal Fiber Reinforced Polyester Composites
(Egerton University, 2012-10) Mutai, A. J; Ogola, W. O; Ondieki, C. M. M
The growing environmental consciousness and understanding of the need for sustainable development has generated interest in the use of natural fibers as reinforcements in polymer composites to replace synthetic fibers such as glass. The aim of this study was to determine the bending strength and hardness values of composite samples from sisal fibers and unsaturated polyester resin as the matrix. Chopped random sisal fibers were mixed with resin at various fiber weight percentages from 5, 10, 15, 20 to 40% sisal fiber. Hand lay- up and cold compression processes were used to produce test samples which were left to cure at 250C. The test samples were supported on knife edges and a roller edge central load applied on them for the three-point bend test. The hardness of the samples was tested on a Vickers micro-hardness testing machine. Results show that the 30%wgt fiber content had the highest value of 51.062 MPa for bending strength properties and 16.1 for hardness value while the unmodified sisal fibers recorded a bending strength of 40.382 MPa and a hardness value of 15 at the same fiber content. The modified sisal fiber has a better bonding between the fibers and matrix compared to unmodified sisal fiber therefore the composite samples could bear more load. It was also observed that surface modification of plant fibers result in superior bonding of the fibers and matrix. Sisal leaves produces fibers that could be used in composite manufacturing for use in roofing, partitioning and furniture applications.

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