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Trace Element Concentrations in Some Traditional Diets Consumed in Selected Parts of Eastern Province of Kenya

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Journal of Environmental Protection 2012年第7期3卷 617-623页

作者： David m. maina Lydia W. Njenga John m. Onyari Benjamin N. Kyalo Department of Chemistry School of Physical Sciences University of Nairobi Nairobi Kenya Institute of Nuclear Science and Technology University of Nairobi Nairobi Kenya

Dietary quality is vital in maintaining sound nutritional status. The ecological conditions thus influence the type of diets and their nutritional quality. The purpose of this study was to determine the trace element/mineral content of some of the commonly consumed diets in machakos, Kitui, makueni and mwingi districts. Decorticated maize, beans and finger millet flour samples were purchased from the local markets. For each category, a total of ten samples were collected from each district. The samples were put in plastic bags, sealed and transported to the laboratory in the Institute of Nuclear Science & Technology, University of Nairobi for preparation and analysis. The cooking of the samples was carried out according to local traditional methods. In the decorticated samples, mean copper concentrations were observed to be below 20 μg·g-1;mean zinc concentrations ranged from 34 to 63 μg·g-1 and mean manganese concentrations were in a similar range of 34 to 78 μg·g-1. The mean iron concentrations were significantly high with a range of 161 μg·g-1 to 287 μg·g-1. A similar trend was observed in the beans where the mean copper concentrations varied from 11 to 33 μg·g-1, mean zinc concentrations ranged from a low value of 24 μg·g-1 to a high value of 35 μg·g-1, mean manganese concentrations varied from 33 μg·g-1 to 98 μg·g-1 and the mean iron concentrations ranged from 227 μg·g-1 to 647 μg·g-1. The cooked muthokoi samples from machakos district had relatively high mean trace element concentrations: manganese—109 μg·g-1;iron—280 μg·g-1;copper—19 μg·g-1;and zinc—41 μg·g-1. The only exception was mean iron concentrations which were extremely high in samples from mwingi District where the concentrations varied from 73 μg·g-1 to 1597 μg·g-1. In finger millet flour, the mean manganese concentrations varied from 95 to 290 μg·g-1, whereas the mean iron concentrations ranged from 127 μg·g-1 to 259 μg·g-1. In contrast, the mean copper and zinc concentrations were low in compariso

关键词： Trace Elements Diets Semi-Arid Kenya

Estimation of Above Ground Biomass in Forests Using Alos Palsar Data in Kericho and Aberdare Ranges

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Open Journal of Forestry 2017年第2期7卷 79-96页

作者： Eunice Wamuyu maina Patroba Achola Odera mwangi James Kinyanjui Department of Geomatic Engineering and Geospatial Information Systems Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya Division of Geomatics School of Architecture Planning and Geomatics University of Cape Town Cape Town South Africa Department of Forestry School of Natural Resources and Environmental Studies Karatina University Karatina Kenya

Above Ground Biomass is one of the six pools identified in the inventory of forest resources and estimation of greenhouse gas emissions and sinks from the forestry sector. The pool varies by management practices in different agro-ecological or agro-climatic zones in forests. The quantification of above ground biomass (AGB) hence carbon sequestration in forests has been very difficult due to the immense costs required. This research was done to estimate AGB using ALOS PALSAR L band data (HH, HV polarisation) acquired in 2009 in relation with ground measurements data in Kericho and Aberdares ranges in Kenya. Tree data information was obtained from ground measurement of DBH and tree heights in 100 circular plots of 15 m radius, by use of random sampling technique. ALOS PALSAR image is advantageous for its active microwave sensor using L-band frequency to achieve cloud free imageries, and the ability of long wavelength cross-polarization to estimate AGB accurately for tropical forests. The variations result between Natural and plantation forest for measured and estimated biomass in Kericho HV band regression value was 0.880 and HH band was 0.520. In Aberdare ranges HV regression value of 0.708 and HH band regression value of 0.511 for measured and estimated biomass respectively. The variations can be explained by the influence of different management regimes induced human disturbances, forest stand age, density, species composition, and trees diameter distribution. However, further research is required to investigate how strong these factors affect relationship between AGB and Alos Palsar backscatters.

关键词： Above Ground Biomass Estimation Green House Gas Carbon Credits Alos Palsar Backscatter Cross-Polarization Regression Analysis

Unravelling Antimicrobial Resistance Phenotypes and Carriage of Extended-Spectrum β-Lactamase Genes in Escherichia coli Isolated from Dairy Farms in Kiambu County, Kenya

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Advances in microbiology 2022年第5期12卷 295-315页

作者： Dan Waithiru John mwaniki Njeru John m. maingi Erastus mulinge Benjamin Ngugi John maina John Kiiru Department of Biochemistry Biotechnology & Microbiology Kenyatta University Nairobi Kenya Centre for microbiology Research Kenya Medical Research Institute Nairobi Kenya

The use of antibiotics for prophylaxis and growth enhancement in livestock farming is on the increase globally. This practice has led to the emergence and spread of antimicrobial-resistant bacteria in livestock. Only limited research has been done to establish the role of cattle farming in antimicrobial resistance. The current study sought to establish the carriage of multi-drug resistance and extended-spectrum beta-lactamase genes in Escherichia coli from farmers, their cattle, and cattle slurry within Kiambu County. A total of 286 (81%) E. coli isolates were recovered from 352 samples analysed. Antibiotic resistance profiles showed 114 (40%) isolates were resistant to ≥3 antimicrobial classes and were considered multidrug-resistant. Among multidrug-resistant (mDR) E. coli strains, 40 (14%) were resistant to 3 different antimicrobial classes, while 71 (25%) were resistant to between 4 and 7 antibiotic classes. Extended-spectrum β-lactamase resistance was found in 18 isolates: human (n = 14), cattle (n = 2), and environmental (n = 2). Both the blaCTX-m and blaTEm genes were detected in 10 and 15 strains, respectively. Sequence analysis showed that the isolates carried the blaTEm-116 (n = 7), blaTEm-1 (n = 5), and blaCTX-m-15 (n = 8) genes. Genotyping mDR isolates using (GTG) 5 PCR demonstrated that the isolates were not clonal. This data shows antimicrobial resistance profiles and different types of resistance genes in the E. coli population on dairy farms. As a result, more effective, targeted public health policies and measures need to be put in place to control and prevent the emergence and spread of resistant bacteria.

关键词： Humans Cattle Slurry Escherichia coli multidrug Resistance Extended-Spectrum β-Lactamase (ESBL) TEm 116 CTX-m-15 Kenya

A Normal Weighted Inverse Gaussian Distribution for Skewed and Heavy-Tailed Data

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Applied mathematics 2022年第2期13卷 163-177页

作者： Calvin B. maina Patrick G. O. Weke Carolyne A. Ogutu Joseph A. m. Ottieno Department of mathematics and Actuarial Science Kisii University Kisii Kenya School of mathematics University of Nairobi Nairobi Kenya

High frequency financial data is characterized by non-normality: asymmetric, leptokurtic and fat-tailed behaviour. The normal distribution is therefore inadequate in capturing these characteristics. To this end, various flexible distributions have been proposed. It is well known that mixture distributions produce flexible models with good statistical and probabilistic properties. In this work, a finite mixture of two special cases of Generalized Inverse Gaussian distribution has been constructed. Using this finite mixture as a mixing distribution to the Normal Variance mean mixture we get a Normal Weighted Inverse Gaussian (NWIG) distribution. The second objective, therefore, is to construct and obtain properties of the NWIG distribution. The maximum likelihood parameter estimates of the proposed model are estimated via Em algorithm and three data sets are used for application. The result shows that the proposed model is flexible and fits the data well.

关键词： Inverse Gaussian Finite mixture Weighted Distribution mixed model Em-Algorithm

Thermal Stress monitoring on Piston Rings by Real Time Holographic Interferometry

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Optics and Photonics Journal 2013年第8期3卷 379-384页

作者： Stephen N. maina Geoffrey K. Rurimo Patrick m. Karimi Dickson m. Kinyua Calvin F. Ominde Department of Physics Jomo Kenyatta University of Agriculture & Technology Nairobi Kenya Department of Physics Kenyatta University Nairobi Kenya

In this paper, real time holographic Interferometry (RTHI) technique was used to monitor the thermal stress on the piston rings. The piston rings holograms were recorded and the holographic plate replaced on the holder after development. The piston ring was subjected to thermal stress as it was illuminated by Laser beam acting as the object beam. This process led to generation of interferograms which were captured by a CCD camera at different temperatures. The captured interferograms were analyzed using atmosfringe version 3.3 software. From the analysis, the peak to valley (P-V) aberrations measured for each of the piston ring varied for the same temperature value. The P-V aberrations ranging from 0.0128λ to 1.2989λ were obtained. From this result, it was evident that the three rings on the piston had different unique structural characteristics due to their function.

关键词： Interferogram Hologram Aberration Piston Ring Laser Beam

A Special Weight for Inverse Gaussian mixing Distribution in Normal Variance mean mixture with Application

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Open Journal of Statistics 2021年第6期11卷 977-992页

Normal Variance-mean mixture (NVmm) provides a general framework for deriving models with desirable properties for modelling financial market variables such as exchange rates, equity prices, and interest rates measur... 详细信息

Normal Variance-Mean Mixture (NVMM) provides a general framework for deriving models with desirable properties for modelling financial market variables such as exchange rates, equity prices, and interest rates measured over short time intervals, i.e. daily or weekly. Such data sets are characterized by non-normality and are usually skewed, fat-tailed and exhibit excess kurtosis. The Generalised Hyperbolic distribution (GHD) introduced by Barndorff-Nielsen (1977) which act as Normal variance-mean mixtures with Generalised Inverse Gaussian (GIG) mixing distribution nest a number of special and limiting case distributions. The Normal Inverse Gaussian (NIG) distribution is obtained when the Inverse Gaussian is the mixing distribution, i.e., the index parameter of the GIG is . The NIG is very popular because of its analytical tractability. In the mixing mechanism, the mix

关键词： Finite mixture Weighted Distribution mixed model Em-Algorithm

A Finite mixture of Generalised Inverse Gaussian with Indexes -1/2 and -3/2 as mixing Distribution for Normal Variance mean mixture with Application

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Open Journal of Statistics 2021年第6期11卷 963-976页

mixture models have become more popular in modelling compared to standard distributions. The mixing distributions play a role in capturing the variability of the random variable in the conditional distribution. Studies have lately focused on finite mixture models as mixing distributions in the mixing mechanism. In the present work, we consider a Normal Variance mean mixture model. The mixing distribution is a finite mixture of two special cases of Generalised Inverse Gaussian distribution with indexes -1/2 and -3/2. The parameters of the mixed model are obtained via the Expectation-Maximization (Em) algorithm. The iterative scheme is based on a presentation of the normal equations. An application to some financial data has been done.

关键词： Finite mixture Weighted Distribution mixed model Em-Algorithm

Interferometry Analysis of Cellophane Birefringence

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Optics and Photonics Journal 2013年第6期3卷 337-341页

作者： Dickson m. Kinyua Geoffrey K. Rurimo Patrick m. Karimi Stephen N. maina Calvin F. Ominde Department of Physics Jomo Kenyatta University of Agriculture & Technology Nairobi Kenya Department of Physics Kenyatta University Nairobi Kenya

This paper reports on a simple approach of determining the ability of a transparent material, such as cellophane to rotate the direction of polarization of a light beam. In order to determine the birefringence of such a material, a mach-Zehnder interferometer is used to generate interference patterns when the cellophane sheet is mounted on one arm such as to intercept a portion of the laser beam. The recorded interferograms show a phase shift which is calculated to be 0.98π radians. By rotating the cellophane sheet on the object beam, the fringe separation is measured for different angles and the values used to calculate the ordinary and extraordinary refractive indices as 1.4721 ± 0.0002 and 1.4680 ± 0.0002 respectively at 632.8 nm wavelength. A surface error of approximately λ/16 (peak to valley) is measured from the recorded interferograms. Because of its sufficient birefringence and small thickness of 24 μm, cellophane can be used to fabricate special polarization pupil masks by cutting and aligning different cellophane structures appropriately.

关键词： Cellophane Sheet Birefrigence Interferrogram Polarization

Total Carbon Stock and Potential Carbon Sequestration Economic Value of mukogodo Forest-Landscape Ecosystem in Drylands of Northern Kenya

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Open Journal of Forestry 2022年第1期12卷 19-40页

作者： Nereoh C. Leley David K. Langat Abdalla K. Kisiwa Geoffry m. maina meshack O. muga Kenya Forestry Research Institute Nairobi Kenya Department of Natural Resources Egerton University Njoro Kenya Food and Agriculture Organization of the United Nations Nairobi Kenya

Carbon sequestration is one of the important ecosystem services provided by forested landscapes. Dry forests have high potential for carbon storage. However, their potential to store and sequester carbon is poorly understood in Kenya. moreover, past attempts to estimate carbon stock have ignored drylands ecosystem heterogeneity. This study assessed the potential of mukogodo dryland forest-landscape in offsetting carbon dioxide through carbon sequestration and storage. Four carbon pools (above and below ground biomass, soil, dead wood and litter) were analyzed. A total of 51 (400 m2) sample plots were established using stratified-random sampling technique to estimate biomass across six vegetation classes in three landscape types (forest reserve, ranches and conservancies) using nested-plot design. Above ground biomass was determined using generalized multispecies model with diameter at breast height, height and wood density as variables. Below ground, soil, litter and dead wood biomass;carbon stocks and carbon dioxide equivalents (CO2eq) were estimated using secondary information. The CO2eq was multiplied by current prices of carbon trade to compute carbon sequestration value. Mean ± SE of biomass and carbon was determined across vegetation and landscape types and mean differences tested by one-way Analysis of Variance. Mean biomass and carbon was about 79.15 ± 40.22 TB ha