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Search Results: 1 - 10 of 50556 matches for " Y. Kibe "
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Hybrid IEEE 802.15.6 Wireless Body Area Networks Interference Mitigation Model for High Mobility Interference Scenarios  [PDF]
Anthony Mile, George Okeyo, Ann Kibe
Wireless Engineering and Technology (WET) , 2018, DOI: 10.4236/wet.2018.92004
Abstract: The field of Wireless Sensor Networks (WSNs) has revolutionized tremendously in the recent past with its major application in Wireless Body Area Networks (WBANs). This has in the same dimension attracted immense interests from the researchers and technology providers. The operational modality of the WBANs is that a few sensor nodes are placed in or around the body and that they are meant to operate within a limited condition while providing high performance in terms of WBAN life time, high throughput, high data reliability, minimum or no delay and low power consumption. As most of the WBAN operates within the universal Industrial, Scientific and Medical (ISM) Narrow Band (NB) wireless band (2.4 Ghz) frequency band, this has posed a challenge in respect to inter, intra and co-channel interference especially in dense areas and high mobility scenarios. As well the body posture changes dynamically due to these mobility effects. In this paper, we propose a hybrid WBAN interference mitigation model based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) Contention Window (CW) approach and User Priority (UP) queues. Using Omnet++ simulation, a comparison to the IEEE 802.15.6 based WBAN protocol is presented under the standing, walking sitting and Lying postural mobility scenarios. The results show that the proposed hybrid model outperforms IEEE 802.15.6 based CSMA/CA protocol in areas of network throughput, bandwidth efficiency and network delay in these mobility postures.
Adaptive Cluster Head Selection Scheme for High Mobility Based IEEE 802.15.6 Wireless Body Area Networks  [PDF]
Anthony Mile, George Okeyo, Ann Kibe
Journal of Sensor Technology (JST) , 2018, DOI: 10.4236/jst.2018.82003
Abstract: Due to the development in the field of Wireless Sensor Networks (WSNs), its major application, Wireless Body Area Network (WBAN) has presently become a major area of interest for the developers and researchers. Efficient sensor nodes data collection is the key feature of any effective wireless body area network. Prioritizing nodes and cluster head selection schemes plays an important role in WBAN. Human body exhibits postural mobility which affects distances and connections between different sensor nodes. In this context, we propose maximum consensus based cluster head selection scheme, which allows cluster head selection by using Link State. Nodal priority through transmission power is also introduced to make WBAN more effective. This scheme results in reduced mean power consumption and also reduces network delay. A comparison with IEEE 802.15.6 based CSMA/CA protocol with different locations of cluster head is presented in this paper. These results show that our proposed scheme outperforms Random Cluster head selection, Fixed Cluster head at head, Foot and Belly positions in terms of mean power consumption, network delay, network throughput and bandwidth efficiency.
The effects of East African low level jet on food security in horn of Africa: A case study of coastal region of Kenya
SM Muti, AM Kibe
African Journal of Food, Agriculture, Nutrition and Development , 2009,
Abstract: Literature on rainfall variability in Eastern Africa has suggested a significant influence from local factors that control rainfall amounts and distribution in contrast to the global wind circulation systems in oceanic atmospheres. All oceans are associated with unique wind systems that reflect temperature and other physical attributes of the water masses. However, the influence of such systems on Eastern Africa has not been investigated in conjunction with unique climatic phenomena, including the June winds in the coastal region of Kenya. This study involved a review of literature and the analyses of secondary data from studies conducted in the region, including 39 years of meteorological data. The results indicated that only two months in a year, namely April and May, experience a positive net moisture regime. In all other months, predicted evaporation exceeds received precipitation. The results also suggest that the annual June winds create a cyclic depression in rainfall amounts during the long rains season, resulting in decreased soil moisture and therefore adverse effects on annual field crops. The June winds, at critical stages of maize growth, results in depressed crop yields that threaten food supply and food security. Maize yields in the region are associated over time with amounts of rain received during the long rains season. Cyclic patterns indicated that a year of higher rainfall alternates with a year of lower rainfall amounts. The study reveals that June winds causes over 95% in yield loses and suggests that the region can feed itself and export excess grains if only appropriate technologies to counter June winds effects are adopted. Since the occurrence of June winds is strongly linked to the La Ni a climatic phenomenon the study suggests development of a maize yield prediction model for seasonal forecasting based on the onset of June winds during the long rains season.
Longevity in Mice Is Promoted by Probiotic-Induced Suppression of Colonic Senescence Dependent on Upregulation of Gut Bacterial Polyamine Production
Mitsuharu Matsumoto, Shin Kurihara, Ryoko Kibe, Hisashi Ashida, Yoshimi Benno
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0023652
Abstract: Background Chronic low-grade inflammation is recognized as an important factor contributing to senescence and age-related diseases. In mammals, levels of polyamines (PAs) decrease during the ageing process; PAs are known to decrease systemic inflammation by inhibiting inflammatory cytokine synthesis in macrophages. Reductions in intestinal luminal PAs levels have been associated with intestinal barrier dysfunction. The probiotic strain Bifidobacterium animalis subsp. lactis LKM512 is known to increase intestinal luminal PA concentrations. Methodology/Principal Findings We supplemented the diet of 10-month-old Crj:CD-1 female mice with LKM512 for 11 months, while the controls received no supplementation. Survival rates were compared using Kaplan–Meier survival curves. LKM512-treated mice survived significantly longer than controls (P<0.001); moreover, skin ulcers and tumors were more common in the control mice. We then analyzed inflammatory and intestinal conditions by measuring several markers using HPLC, ELISA, reverse transcription-quantitative PCR, and histological slices. LKM512 mice showed altered 16S rRNA gene expression of several predominant intestinal bacterial groups. The fecal concentrations of PAs, but not of short-chain fatty acids, were significantly higher in LKM512-treated mice (P<0.05). Colonic mucosal function was also better in LKM512 mice, with increased mucus secretion and better maintenance of tight junctions. Changes in gene expression levels were evaluated using the NimbleGen mouse DNA microarray. LKM512 administration also downregulated the expression of ageing-associated and inflammation-associated genes and gene expression levels in 21-month-old LKM512-treated mice resembled those in 10-month-old untreated (younger) mice. Conclusion/Significance Our study demonstrated increased longevity in mice following probiotic treatment with LKM512, possibly due to the suppression of chronic low-grade inflammation in the colon induced by higher PA levels. This indicates that ingestion of specific probiotics may be an easy approach for improving intestinal health and increasing lifespan. Further studies are required to clarify its effectiveness in humans.
Production Functions and Their Use in Predicting Chickpea Biomass Yields When Grown under Varying Tillage and Sowing Dates in Naivasha, Kenya
A.M. Kibe,C.N. Onyari
Agricultural Journal , 2013,
Abstract: The use of production functions as tools for analyzing agronomic relationships and crop growth is gaining importance the world over. Their predictive value in crop adaptation trials for specific agro-ecological sites particularly in semi arid lands is of special interest, but little, if any work is being done with this regard in Kenya. A chickpea (Cicer arietinum L.) cultivar, ICCV 95423 was therefore planted under four tillage systems namely, Conventional (CT), Double Digging (DD), Furrow (FT) and Strip Tillage (ST) and under three sowing dates (two weeks apart) at Naivasha. The aim was to develop evapotranspiration and biomass yield (ET-yield) relationships and determining their potential use in analyzing growth (LAI and DM production) of chickpea. Estimated yields (computed) were produced using the 1st season`s (Jan-May `05) functions and validated with the 2nd season (Jun-Oct 05) actual yield data sets. The relationships exhibited very high regression correlation coefficients (R2>0.93) indicating the potential reliability of the functions in predicting chickpea yields. Rate of increase in biomass production per hectare millimeter increase in water use was 17.5kg ha-mm 1. Biomass yields estimated from season II ET data were validated and had a reliability of 0.859 and 0.952 when linear and curvilinear functions were fitted, respectively. The January to June crop produced DM at a higher rate of 685.2 kg ha 1 per unit LAI as compared to 309 kg ha 1 LAI -1 for season II crop. Quadratic functions proved able to account for more variations in DM production than linear functions. They can therefore, be used reliably in analyzing and predicting DM production of chickpea in Naivasha. Chickpea has great agronomic potential for use as a food and forage crop in the dry highlands of Kenya.
Production Potential of Desi Chickpea Grown under Various Nitrogen and Planting Densities at Naivasha
A.M. Kibe,D.K. Kamithi
Agricultural Journal , 2013,
Abstract: The erratic nature of rainfall in the Kenyan semi arid highland regions, such as Naivasha, coupled with the high dependency on maize grain, usually results in relatively low and unstable yields. Chickpea is mainly cultivated as a rain-fed crop and water stress often affects both productivity and yield stability. Potential seed yield has been reported not to exceed 1.5 t ha 1 in other countries but information on optimum nitrogen and Plant Population Density (PPD) has not been developed for Naivasha region. Therefore, A desi chickpea variety ICCV 97105 was grown in two seasons at NAHRC, KARI (Naivasha). Viz., February 27th-June 24 and June 30th to Oct 26th of 2005; in a RCBD with 4 levels of nitrogen (0; 20; 40 and 60 kg N 1) and 4 planting densities (i.e., 74,074; 89,889; 111,111 and 148,148 seeds ha 1). Maximum above ground biomass obtained was 5.06 and 4.37 tones ha 1 for the first and second seasons, respectively. Application of 60 kg N 1 produced 62 and 68% more biomass (DM) than the no N application treatment. The curvilinear response of above ground biomass to added levels of N with high coefficients of 0.944 and 0.989 in respective seasons signifies the possibility of increasing further chickpea biomass. Maximum grain yields were 2.57 and 1. 66 t ha 1 in season I and II, respectively, a difference of 54.8%. This was attributed to the higher rainfall of 235 mm received in Season I as compared to 176.8 for season II, a difference of 76.2 mm water. The response of above ground biomass and grain yield to increasing PPD was found to be linear with very high regression coefficients of over 0.993 in both seasons. This revealed the strong dependency of chickpea grain yields on PPD. Harvest Indices (HI) ranged between 0.42 and 0.72. Application of 20 kg N 1 produced a HI of about 0.6 and 0.5, in seasons I and II, respectively. Increase in planting population up to approximately 105,000 plants ha 1 was observed to increase the harvest index of chickpea to over 0.6 and 0.41 in seasons I and II, respectively. Further increase in plant density beyond 110,000 plants ha 1, however caused a decline in the rate of increase in HI of chickpea. Chickpea can be successfully grown in Naivasha during February to June and June to October seasons. Further research work is however, recommended with the aim of determining chickpea productivity under higher PPD, various watering regimes and agro-ecological environments.
Community based vector control in Malindi, Kenya
L W Kibe, C M Mbogo, J Keating, S Molyneux, J I Githure, J C Beier
African Health Sciences , 2006,
Abstract: Background: Community involvement has become an important component of the National Malaria Control Strategy in Kenya, resulting in the organization of groups charged with addressing mosquito and malaria-related concerns within the community. Objectives: The purpose of this study was to identify community groups involved with intended malaria vector control activity in Malindi, Kenya. Methods: Information was obtained from key informant interviews, focus group discussions, and a stakeholder meeting. The objectives were to determine the roles of community groups, identify examples of past successes and obstacles to successful implementation of vector control, and assess the level of knowledge about malaria and mosquitoes among the groups. Results: Nineteen of 34 community groups (56%) registered at social services reported intended malaria vector control activities such as treating ditches, making and selling insecticide-treated mosquito nets, draining stagnant water, organizing clean-ups, making and selling neem soap, and the organization of campaigns such as the “Malaria Mosquito Day”. Major challenges facing these groups include volunteerism, lack of technical expertise, supervision, and maintaining control activities in the absence of funds. Most groups reported limited knowledge about malaria vectors, and thus targeted all water bodies for control activities. Conclusions: We found that community groups are willing to participate in control operations, but lack government and technical support. We highlight the importance of strengthening organizational efforts and capacity building, as well as the need to clarify government policy on malaria vector control responsibilities within the communities
Mission design of LiteBIRD
T. Matsumura,Y. Akiba,J. Borrill,Y. Chinone,M. Dobbs,H. Fuke,A. Ghribi,M. Hasegawa,K. Hattori,M. Hattori,M. Hazumi,W. Holzapfel,Y. Inoue,K. Ishidoshiro,H. Ishino,H. Ishitsuka,K. Karatsu,N. Katayama,I. Kawano,A. Kibayashi,Y. Kibe,K. Kimura,N. Kimura,K. Koga,M. Kozu,E. Komatsu,A. Lee,H. Matsuhara,S. Mima,K. Mitsuda,K. Mizukami,H. Morii,T. Morishima,S. Murayama,M. Nagai,R. Nagata,S. Nakamura,M. Naruse,K. Natsume,T. Nishibori,H. Nishino,A. Noda,T. Noguchi,H. Ogawa,S. Oguri,I. Ohta,C. Otani,P. Richards,S. Sakai,N. Sato,Y. Sato,Y. Sekimoto,A. Shimizu,K. Shinozaki,H. Sugita,T. Suzuki,A. Suzuki,O. Tajima,S. Takada,S. Takakura,Y. Takei,T. Tomaru,Y. Uzawa,T. Wada,H. Watanabe,N. Yamasaki,M. Yoshida,T. Yoshida,K. Yotsumoto
Physics , 2013, DOI: 10.1007/s10909-013-0996-1
Abstract: LiteBIRD is a next-generation satellite mission to measure the polarization of the cosmic microwave background (CMB) radiation. On large angular scales the B-mode polarization of the CMB carries the imprint of primordial gravitational waves, and its precise measurement would provide a powerful probe of the epoch of inflation. The goal of LiteBIRD is to achieve a measurement of the characterizing tensor to scalar ratio $r$ to an uncertainty of $\delta r=0.001$. In order to achieve this goal we will employ a kilo-pixel superconducting detector array on a cryogenically cooled sub-Kelvin focal plane with an optical system at a temperature of 4~K. We are currently considering two detector array options; transition edge sensor (TES) bolometers and microwave kinetic inductance detectors (MKID). In this paper we give an overview of LiteBIRD and describe a TES-based polarimeter designed to achieve the target sensitivity of 2~$\mu$K$\cdot$arcmin over the frequency range 50 to 320~GHz.
Laboratory Studies on the Removal of Radon-Born Lead from KamLAND's Organic Liquid Scintillator
G. Keefer,C. Grant,A. Piepke,T. Ebihara,H. Ikeda,Y. Kishimoto,Y. Kibe,Y. Koseki,M. Ogawa,J. Shirai,S. Takeuchi,C. Mauger,C. Zhang,G. Schweitzer,B. E. Berger,S. Dazeley,M. P. Decowski,J. A. Detwiler,Z. Djurcic,D. A. Dwyer,Y. Efremenko,S. Enomoto,S. J. Freedman,B. K. Fujikawa,K. Furuno,A. Gando,Y. Gando,G. Gratta,S. Hatakeyama,K. M. Heeger,L. Hsu,K. Ichimura,K. Inoue,T. Iwamoto,Y. Kamyshkov,H. J. Karwowski,M. Koga,A. Kozlov,C. E. Lane,J. G. Learned,J. Maricic,D. M. Marko,S. Matsuno,D. McKee,R. D. McKeown,T. Miletic,T. Mitsui,M. Motoki,K. Nakajima,K. Nakajima,K. Nakamura,T. O'Donnell,H. Ogawa,F. Piquemal,J. -S. Ricol,I. Shimizu,F. Suekane,A. Suzuki,R. Svoboda,O. Tajima,Y. Takemoto,K. Tamae,K. Tolich,W. Tornow,Hideki Watanabe,Hiroko Watanabe,L. A. Winslow,S. Yoshida,for the KamLAND Collaboration
Physics , 2013,
Abstract: The removal of radioactivity from liquid scintillator has been studied in preparation of a low background phase of KamLAND. This paper describes the methods and techniques developed to measure and efficiently extract radon decay products from liquid scintillator. We report the radio-isotope reduction factors obtained when applying various extraction methods. During this study, distillation was identified as the most efficient method for removing radon daughters from liquid scintillator.
Examining the determinants of mosquito-avoidance practices in two Kenyan cities
Kate Macintyre, Joseph Keating, Stephen Sosler, Lydiah Kibe, Charles M Mbogo, Andrew K Githeko, John C Beier
Malaria Journal , 2002, DOI: 10.1186/1475-2875-1-14
Abstract: Data from two cities in Kenya were gathered using a household survey and a two-stage cluster sample design. The cities were stratified based on planning and drainage observed across the urban areas. This helped control for the strong environmental and topographical variation that we assumed influences mosquito ecology. Individual interviews given to each household included questions on socio-economic status, education, housing type, water source, rubbish disposal, mosquito-prevention practices and knowledge of mosquitoes. In multivariate regression, factors measuring wealth, education level, and the communities' level of planning and drainage were used to estimate the probability that a household engages in multiple mosquito-avoidance activities, or has all members sleeping under a bed net.Our analysis shows that people from wealthier, more educated households were more likely to sleep under a net, in Kisumu (OR = 6.88; 95% CI = 2.56,18.49) and Malindi (OR = 3.80; 95% CI = 1.91,7.55). Similarly, the probability that households use several mosquito-prevention activities was highest among the wealthiest, best-educated households in Kisumu (OR = 5.15; 95% CI = 2.04,12.98), while in Malindi household wealth alone is the major determinant.We demonstrate the importance of examining human-mosquito interaction in terms of how access to resources may enhance human activities. The findings illustrate that the poorest segments of society are already doing many things to protect themselves from being bitten, but they are doing less than their richer neighbours.Malaria remains an enormous public health problem in much of sub-Saharan Africa. In the past, malaria transmission was most notably associated with rural environments, as a result of the mosquito's affinity for clean, sunlit, temporary pools of water, which dominate rural landscapes in Africa [1,2]. There is however, evidence of urban malaria transmission [3,4]. Moreover, Robert et al. [5] identified market-garden wells a
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