OALib Journal期刊

ISSN: 2333-9721




2020 ( 38 )

2019 ( 87 )

2018 ( 98 )

2017 ( 105 )


匹配條件: “ John Wanjala Makokha” ,找到相關結果約32542條。
Thermodynamic Properties of Yttrium Based Cuprate Due to Electron-Cooper Pair Interaction Using BVT  [PDF]
Abel Wamalwa Mukubwa, Jared Oloo Odhiambo, John Wanjala Makokha
Open Access Library Journal (OALib Journal) , 2018, DOI: 10.4236/oalib.1104880
Since the discovery of high temperature superconductivity (HTSC), there have been varied results concerning the high pairing energy in the unconventional superconductivity. In an attempt to unearth the mechanism behind the high pairing energy, we study a model in which an excited electron interacts with a Cooper pair. The interaction was studied earlier on using second quantization which depended on a wave function. We now use Bogoliubov-Valatini trans-formation (BVT) that is independent of the wave function to study the thermodynamic properties due to the interaction between an electron and a Cooper pair in a Yttrium based cuprate. The interaction energy increases with temperature and at ; we record the interaction energy of 2.173 meV and the specific heat of 4.669 J·mol·1·K·1. The entropy of this system is found to be 5.11 mJ·g·1·K·1. The Sommerfeld’s coefficient is maximum at where . It has also been observed, for the first time, that the thermodynamic quantities of YBCO123 are constant when temperature varies between 0 K and 18 K. Above 18 K, the thermodynamic quantities rise sharply. This observation has been attributed to the pairing of electrons in the singlet-s and singlet-p states.
EDXRF Spectroscopic Elemental Analysis for Efficacy of Kibabii University Sewage Treatment System  [PDF]
Yonah Situma, Jared Oloo Odhiambo, John Wanjala Makokha
Open Access Library Journal (OALib Journal) , 2018, DOI: 10.4236/oalib.1104992
Elemental analysis of sewage effluents in Kibabii sewage treatment system was achieved via Energy-Dispersive X-Ray Fluorescence (EDXRF) spectroscopy with the aim of assessing the efficacy of the treatment system. Concentrations of lead (Pb), mercury (Hg), cadmium (Cd) and arsenic (As) were measured based on clay soil “standards” in concentration range for Pb, Hg and As as 12.7 ppm, 14.3 ppm and 8.83 ppm respectively for certification. Among other probable reference materials, clay soil “standards” were used for certification in this work because of similarity in matrix composition with the sediments. The concentration for Hg, Pb, and As in the sewage sediments were 10.65 ± 2.28 ppm, 8.86 ± 2.92 ppm and 3.41 ± 2.18 ppm respectively in lagoon A. In lagoon B the levels were 3.82 ± 0.56 ppm, 6.35 ± 1.50 ppm and 1.67 ± 0.53 ppm respectively. Lagoon C showed a reduction in the levels with 3.74 ± 1.39 ppm for Hg and 2.30 ± 0.27 ppm for Pb. As was not detected in lagoon C, on the other hand, Cd was not detected in all the lagoons. The efficacies in the treatment varied from 30.34% - 51.78%, 37.63% - 65.41% and 76.63% - 84.81% for lagoon A, B and C respectively. The study was successful in quantifying the heavy elements in the lagoons from which the efficacy in the treatment process was determined. The study provided awareness on the elemental concentration levels in the Kibabii University sewage treatment system, hence creating awareness on what is released into River Kibabii. With this information, the surrounding community and the University can partner in order to mitigate the effects of heavy metals in the effluents in future due to the growth of the University day by day.
A Radiological Survey in Tailings: A Case Study of Rosterman Gold Mine, Western Kenya  [PDF]
Conrad Khisa Wanyama, John Wanjala Makokha, Fred Wekesa Masinde
Open Access Library Journal (OALib Journal) , 2020, DOI: 10.4236/oalib.1106293
Abstract: Thirty samples of tailing waste weighing 200 g were randomly collected from both active and inactive tunnels at the Rosterman gold mine site in western Kenya. The average activity concentration of the radionuclides (40K, 232Th and 238U) analyzed by the gamma-ray spectrometry in the tailing samples was 260 ± 14.29 Bq/Kg for 40K, 118 ± 8.25 Bq/Kg for 232Th and 81 ± 3.63 Bq/Kg for 238U. The corresponding radiological parameters for all the collected thirty tailing waste samples were determined from the specific mean activity concentrations. The average dose rate for all the samples was 54 nGy/h. The average radium equivalent value was 262 ± 12.04 Bq/Kg with a range of 154 ± 6.42 Bq/Kg to 350 ± 10.24 Bq/Kg. The average values of external and internal indices were 0.6 ± 0.03 mSv/y and 0.7 ± 0.04 mSv/y respectively. The average indoor and outdoor annual effective dose rates that were determined for this study were 0.3 ± 0.02 and 0.2 ± 0.01 respectively. Therefore, the tailing samples recorded doses and radiological indices below the world average permissible values. This implies that the radiation exposure to the miners and general public due to tailing wastes at Rosterman gold mine poses no significant health risk.
Spatial-Temporal Characterization of Atmospheric Aerosols via Airborne Spectral Imaging and Growing Hierarchical Self-Organizing Maps  [PDF]
John W. Makokha, Jared O. Odhiambo
Journal of Geoscience and Environment Protection (GEP) , 2018, DOI: 10.4236/gep.2018.66008
Abstract: Neural network analysis based on Growing Hierarchical Self-Organizing Map (GHSOM) is used to examine Spatial-Temporal characteristics in Aerosol Optical Depth (AOD), ?ngstr?m Exponent (?E) and Precipitation Rate (PR) over selected East African sites from 2000 to 2014. The selected sites of study are Nairobi (1°S, 36°E), Mbita (0°S, 34°E), Mau Forest (0.0° - 0.6°S; 35.1°E - 35.7°E), Malindi (2°S, 40°E), Mount Kilimanjaro (3°S, 37°E) and Kampala (0°N, 32.1°E). GHSOM analysis reveals a marked spatial variability in AOD and ?E that is associated to changing PR, urban heat islands, diffusion, direct emission, hygroscopic growth and their scavenging from the atmosphere specific to each site. Furthermore, spatial variability in AOD, ?E and PR is distinct since each variable corresponds to a unique level of classification. On the other hand, GHSOM algorithm efficiently discriminated by means of clustering between AOD, ?E and PR during Long and Short rain spells and dry spell over each variable emphasizing their temporal evolution. The utilization of GHSOM therefore confirms the fact that regional aerosol characteristics are highly variable be it spatially or temporally and as well modulated by PR received over each variable.
Trend Analysis of Aerosol Optical Depth and Ångström Exponent Anomaly over East Africa  [PDF]
John W. Makokha, Jared O. Odhiambo, Juma S. Godfrey
Atmospheric and Climate Sciences (ACS) , 2017, DOI: 10.4236/acs.2017.74043
Abstract: Trend analysis of atmospheric aerosols enhances confidence in the evaluation of both direct and indirect effects of aerosols on regional climate change. To comprehensively achieve this over East Africa, it’s important to understand aerosols temporal characteristics over well selected sites namely Nairobi (1°S, 36°E), Mbita (0°S, 34°E), Mau Forest (0.0°S - 0.6°S; 35.1°E - 35.7°E), Malindi (2°S, 40°E), Mount Kilimanjaro (3°S, 37°E) and Kampala (0°N, 32.1°E). In this context, trend analysis (annual (in Aerosol Optical Depth (AOD) at 550 nm and Ångström Exponent Anomaly (
Long Term Assessment of Aerosol Radiative Forcing over Selected Sites of East Africa  [PDF]
John W. Makokha, Jared O. Odhiambo, Juma Godfrey Shem
Journal of Geoscience and Environment Protection (GEP) , 2018, DOI: 10.4236/gep.2018.64002
Abstract: Atmospheric aerosols have contributed to radiative forcing through direct and indirect mechanisms. Aerosol effects are important in computing radiative forcing estimates for the past, current and future climate. In this study, a comprehensive assessment of regional aerosol radiative forcing, Optical Properties of Aerosol and Clouds (OPAC) model (wavelength range of 0.25 - 4.0 μm) over selected sites in East Africa was done. Aerosol optical properties constituted the inputs of a Radiative Transfer Model (RTM). Op-tical properties investigated included Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA) and Asymmetry Parameter (AP). Aerosol Radiative Forcing (ARF) during the study period at the surface (SFC), top of the atmosphere (TOA) and the atmosphere (ATM) was estimated to be -18.4 ± 1.4 W·m-2, +1.1 ± 0.3 W·m-2 and +19.5 ± 2.5 W·m-2, respectively. This corresponds to an increment in net atmospheric forcing at a heating rate of about 0.55 ± 0.05 K/day (0.41 ± 0.03 to 0.78 ± 0.03 K/day) in the lower troposphere. The study points out the significant role played by atmospheric aerosols in climate modification over the area of study. It is recommended that a further assessment be done in view of uncertainties that may impact on the findings and which were not within the scope of this research.
Invasion of Cestrum aurantiacum Lindl. in Kenya  [PDF]
Josephat Makokha
Journal of Environmental Protection (JEP) , 2018, DOI: 10.4236/jep.2018.96042
Abstract: Many forest ecosystems in Kenya are at risk from the invasion of exotic plant species that pose numerous threats like decreasing biodiversity, deteriorating ecosystem processes and degrading their services. They also affect human, other animal health and various angles of the general economy. Cestrum aurantiacum Lindl. is a species with invasive reputation having been reported with very high biological success rating and has been noted in parts of Kenya in proportions that raise concerns. It has negative effects on other plants and animal species function and diversity. These impacts have been recorded in Kenya and elsewhere in this review, I synthesized data from studies that have examined the taxonomy of Cestrum aurantiacum, how this species become part of the ecosystem in Kenya and its ecological and economic impacts. I sourced relevant articles from the internet using keywords relating to the taxonomy, impacts and reports of invasive species and narrowed to records from different parts of Kenya. In this review, I looked across twenty-seven studies, on Cestrum aurantiacum in Kenya and went ahead to review one hundred and thirteen other articles for expanded discussion. Species data in published articles from different parts of Kenya were used as georefences to model overall species distribution which was noted to lie between Mt Kenya, Mt Elgon-Nandi hills and Cherangani hills. It was clearly established that there are major adverse effects associated with species. First, it can change native ecosystem processes such as nutrient cycle or hydrology and contribute significant role on the decrease of native species. A primary risk of Cestrum aurantiacum is that when this species alters the biodiversity, ecosystems are transformed into new configurations with unpredictable consequences to humans and other wildlife in totality. Despite the few positive applications of cestrum species, these can’t compensate for the enormous detrimental consequences associated with the species. Cestrum aurantiacum was introduced in Kenya as an ornamental plant in 1921 by the government and was distributed in several regions of high potential Kenya due to high level of hybridization within the genera, several variables of the species occur. By examining the level of information regarding the taxonomy and impacts of Cestrum aurantiacum on animal and plant species, this study provides pivotal information at the country level with a view to informing monitoring and conservation efforts, such as alien plant removal and control programmes, and
Optical Characterization of Atmospheric Aerosols via Airborne Spectral Imaging and Self-Organizing Map for Climate Change Diagnostics  [PDF]
John W. Makokha, Jared O. Odhiambo
Open Access Library Journal (OALib Journal) , 2018, DOI: 10.4236/oalib.1104698
Self-Organizing Map (SOM) analysis is used to perform optical characteri- zation of both Aerosol Optical Depth (AOD) and Angstrom Exponent (AE) retrieved from Moderate-resolution Imaging Spectroradiometer (MODIS) in relation to Precipitation Rate (PR) from Tropical Rainfall Measurement Mission (TRMM) over selected East African sites from 2000 to 2014 and further diagnose climate change over the region if any. SOM reveals a marked spatial variability in AOD and AE that is associated to changing aerosol transport, urban heat islands, diffusion, direct emission, hygroscopic growth and their scavenging from the atmosphere specific to each site. Temporally, all sites except Mbita and Kampala indicate two clusters in AOD that are associated to prevailing dry and wet seasons over East Africa. Moreover, all sites except Mbita and Mount Kilimanjaro show two clusters in AE that are related to aerosol mode of generation and composition over the region. The single cluster in AOD and ?E over Mbita indicate that aerosol characteristics over the site are influenced by biomass burning and local air circulation rather than the monsoon precipitation throughout the study period.
Identification of malaria transmission and epidemic hotspots in the western Kenya highlands: its application to malaria epidemic prediction
Christine L Wanjala, John Waitumbi, Guofa Zhou, Andrew K Githeko
Parasites & Vectors , 2011, DOI: 10.1186/1756-3305-4-81
Abstract: The study was conducted in five sites in the western Kenya highlands, two U-shaped valleys (Iguhu, Emutete), two V-shaped valleys (Marani, Fort-Ternan) and one plateau (Shikondi) for 16 months among 6-15 years old children. Exposure to malaria was tested using circum-sporozoite protein (CSP) and merozoite surface protein (MSP) immunochromatographic antibody tests; malaria infections were tested by microscopic examination of thick and thin smears, the children's homes were georeferenced using a global positioning system. Paired t-test was used to compare the mean prevalence rates of the sites, K-function was use to determine if the clustering of malaria infections was significant.The mean antibody prevalence was 22.6% in Iguhu, 24% in Emutete, 11.5% in Shikondi, 8.3% in Fort-Ternan and 9.3% in Marani. The mean malaria infection prevalence was 23.3% in Iguhu, 21.9% in Emutete, 4.7% in Shikondi, 2.9% in Fort-Ternan and 2.4% in Marani. There was a significant difference in the antibodies and malaria infection prevalence between the two valley systems, and between the two valley systems and the plateau (P < 0.05). There was no significant difference in the antibodies and malaria infection prevalence in the two U-shaped valleys (Iguhu and Emutete) and in the V-shaped valleys (Marani and Fort Ternan) (P > 0.05). There was 8.5- fold and a 2-fold greater parasite and antibody prevalence respectively, in the U-shaped compared to the V-shaped valleys. The plateau antibody and parasite prevalence was similar to that of the V-shaped valleys. There was clustering of malaria antibodies and infections around flat areas in the U-shaped valleys, the infections were randomly distributed in the V-shaped valleys and less clustered at the plateau.This study showed that the V-shaped ecosystems have very low malaria prevalence and few individuals with an immune response to two major malaria antigens and they can be considered as epidemic hotspots. These populations are at higher risk of se
Seasonal Variability in Aerosol Microphysical Properties over Selected Rural, Urban and Maritime Sites in Kenya  [PDF]
Geoffrey W. Khamala, Jared O. Odhiambo, John W. Makokha
Open Access Library Journal (OALib Journal) , 2018, DOI: 10.4236/oalib.1104821
Atmospheric aerosols are posing a great threat to the already stressed climate with the effects being felt more on African continent. Their presence and interaction with the clouds contribute to the strongest uncertainty in aerosol characteristics and Earth’s energy budget hence; calling for a long term assessment to be done. The present study analyses long term spatiotemporal microphysical aerosol characteristics (namely: effective radius and surface-area concentration), using AErosolROboticNETwork (AERONET) framework over Kenyan urban atmosphere (Nairobi-1°S, 36°E), rural atmosphere (ICIPE-Mbita-0°S, 34°E) and maritime atmosphere (CRPSM-Malindi-2°S, 40°E). AERONET framework was used due to its availability over the selected sites; it is also located in sites that provided contrasting aerosols type, source and characteristics and due to its syner-gism with other frameworks. The findings indicated a spatial and temporal variability in microphysical properties over CRPSM-Malindi, Nairobi and ICIPE-Mbita. CRPSM-Malindi is dominated with coarse aerosols in all sea-sons while Nairobi with coarse mode in the DJF and MAM seasons. ICIPE-Mbita is on the other hand dominated with fine aerosols in all season. In terms of size distribution, the three AERONET sites displayed a bimodal distribution inflecting at 0.44 μm and fine mode radius of 0.15 μm while CRPSM-Malindi recorded a coarse mode of 3.86 μm and Nairobi and ICIPE-Mbita with 5.06 μm. The coarse aerosols have a higher concentration than the fine aerosols in all AERONET sites because of aerosol coagulation and dominance of certain type of aerosols that are coarse in nature.

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