School of Pure and Applied Sciences


Recent Submissions

Now showing 1 - 14 of 14
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    Application of Asymmetric-GARCH Type Models to The Kenyan Exchange Rates
    (EJ-MATH, European Journal of Mathematics and Statistics, 2023-08-31) Wagala , Adolphus;
    Modelling and forecasting the volatility of a financial time series has become essential in many economic and financial applications like portfolio optimization and risk management. The symmetric-GARCH type models can capture volatility and leptokurtosis. However, the models fail to capture leverage effects, volatility clustering, and the thick tail property of high-frequency financial time series. The main objective of this study was to apply the asymmetric-GARCH type models to Kenyan exchange to overcome the shortcomings of symmetric-GARCH type models. The study compared the asymmetric Conditional Heteroskedasticity class of models: EGARCH, TGARCH, APARCH, GJR-GARCH, and IGARCH. Secondary data on the exchange rate from January 1993 to June 2021 were obtained from the Central Bank of Kenya website. The best fit model is determined based on parsimony of the Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC), Log Likelihood criterion, and minimisation of prediction production errors (Mean error [ME] and Root Mean Absolute error [RMAE]). The optimal variance equation for the exchange rates data was APARCH (1,1) - ARMA (3,0) model with a skewed normal distribution (AIC = -4.6871, BIC = -4.5860). Volatility clustering was present in exchange rate data with evidence of the leverage effect. Estimated Kenya’s exchange rate volatility narrows over time, indicating sustained exchange rate stability
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    The Isolation, Screening, and Characterization of Polyhydroxyalkanoate-Producing Bacteria from Hypersaline Lakes in Kenya
    (Journal of Bacteria, 2023-05-08) Omare, Godfrey M.; Muigano, Martin N.;
    Extremophilic microorganisms such as those that thrive in high-salt and high-alkaline en vironments are promising candidates for the recovery of useful biomaterials including polyhydrox yalkanoates (PHAs). PHAs are ideal alternatives to synthetic plastics because they are biodegrada ble, biocompatible, and environmentally friendly. This work was aimed at conducting a bioprospec tion of bacteria isolated from hypersaline-alkaliphilic lakes in Kenya for the potential production of PHAs. In the present study, 218 isolates were screened by Sudan Black B and Nile Red A staining. Of these isolates, 31 were positive for PHA production and were characterized using morphological, biochemical, and molecular methods. Through 16S rRNA sequencing, we found that the isolates belonged to the genera Arthrobacter spp., Bacillus spp., Exiguobacterium spp., Halomonas spp., Para coccus spp., and Rhodobaca spp. Preliminary experiments revealed that Bacillus sp. JSM-1684023 iso lated from Lake Magadi had the highest PHA accumulation ability, with an initial biomass-to-PHA conversion rate of 19.14% on a 2% glucose substrate. Under optimized fermentation conditions, MO22 had a maximum PHA concentration of 0.516 g/L from 1.99 g/L of cell dry weight and 25.9% PHA conversion, equivalent to a PHA yield of 0.02 g/g of biomass. The optimal PHA production media had an initial pH of 9.0, temperature of 35 °C, salinity of 3%, and an incubation period of 48 h with 2.5% sucrose and 0.1% peptone as carbon and nitrogen sources, respectively. This study suggests that bacteria isolated from hypersaline and alkaliphilic tropical lakes are promising candi dates for the production of polyhydroxyalkanoates.
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    Extracts of Jamun seeds inhibited the growth of human (Hep‑2) cancer cells
    (Journal of Cancer Research and Therapeutics | Published by Wolters Kluwer - Medknow, 2023-04-07) . Mauti , Godfrey O
    Introduction: In the last century, the human laryngeal epithelioma has become a life‑threatening disease leading to a high rate of mortality worldwide. The current investigation is focusing on the antiproliferative effect of Eugenia jambolana seed extracts against Hep‑2 cancer cells. Methods: The active compounds from the seeds of E. jambolana were extracted by the decoction extraction method using acetone, ethanol, and methanol. The filtrates from the different solvents were subjected to liquid‑liquid separation before drying by a rotary evaporator. In various doses, the crude extracts and carcinoma were subjected to a methylthiazolyl diphenyl tetrazolium bromide assay. Cell viability was determined under ultraviolet visualization at an absorbance of 540 nm. The data of the viable cells were subjected to analysis of variance at P ≤ .01. Results: Crude compounds of E. jambolana seeds extracted by acetone, methanol, and methanol extract had an anticarcinoma effect. Among the extracts, methanol extract possessed a recommendable anti‑carcinoma effect compared to acetone and ethanol crude extracts. At a concentration of 125 µg/mL, the crude extracts of methanol, acetone, and ethanol destroyed 49.57, 35.01, and 27.67 carcinomas, respectively. The concentration of 31.25 µg/mL of acetone extract and 125 µg/mL of ethanolic extract affected 28.11 and 27.67 carcinomas, respectively. Conclusions: E. jambolana seeds possess anticarcinoma potency and thus can be administered in the reduction of proliferative carcinoma. The study recommended further studies which will involve the elution of pure compounds from the methanol extract of E. jambolana that possess antitumour and antiproliferative activity against Hep‑2 cell lines.
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    Effect of lactic acid bacteria fermentation on nutrients and anti-nutrients of African black nightshade and African spider plant
    (ELSEVIER, 2023-06-14) Wafula, Eliud Nalianya;
    African black nightshade is a leafy vegetable consumed in many parts of Africa. African spi der plant is also a very important indigenous leafy vegetable consumed all around Africa. Both the African black nightshade and African spider plant are popular despite their te dious preparation techniques which involve boiling and discarding the first water or a lengthy boiling duration to remove bitterness. However, this preparation technique reduces heat-labile and water-soluble nutrients. Fermentation can be a better alternative process ing technique since it has been observed that fermented products have better nutritional content and increased safety. However, there is still limited literature on the effect of fermentation on the nutrients and anti-nutrients content of these vegetables. This study aimed to ferment African black nightshade and African spider plant using Lactobacillus fermentum and Lactococcus lactis cultures and determined the effect of the fermentation on their nutrients and anti-nutrients content. Both vegetables were submerged in a 3% sugar and 3% salt brine solution. Total ash, crude proteins and crude fibres significantly increased in starter culture inoculated vegetables. However, both β-carotene and ascorbic acid were slightly reduced in all fermented batches. Anti-nutrients were significantly re duced in all fermented batches. In conclusion, lactic acid fermentation of these vegetables demonstrated the ability to maintain or increase nutrients while reducing of anti-nutrients
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    Antibacterial Potency of Allium sativum, Psidium guajava, Zingiber officinale Roots against the Food Poisoning Strains (Escherichia coli 0157:H7 and Staphylococcus aureus)
    (Tanzania Journal of Science, 2022-12-16) Mauti, Godfrey O.
    Escherichia coli 0157:H7 and Staphylococcus aureus are notorious food poisoning bacteria of great effect on human health. This study determined the phytochemical constituents of ethanolic, vacuum liquid chromatography (VLC) filtrates of Allium sativum (garlic), Psidium guajava (guava), Zingiber officinale (ginger) and their antibacterial activities on E. coli 0157:H7 and S. aureus. In a laboratory-based controlled experiment, the antibacterial and inhibitory activities of the VLC filtrates in doses of 0.01, 0.02, 0.04, and 0.08g/mL were investigated on E. coli 0157:H7 and S. aureus using the agar well diffusion method and compared with a standard antibiotic. The indices of the zone of inhibition on the agar plates were subjected to analysis of variance (p = 0.01). Phytochemical analysis revealed a high concentration of glycosides, steroids, tannins, terpenoids, and the absence of flavonoids in A. sativum. P. guajava root contained a high concentration of glycosides, steroids, tannins, and terpenoids. Z. officinale possessed a high concentration of alkaloids, glycosides, flavonoids, steroids, and terpenoids. Statistically, 0.02 g/mL of Z. officinale (12.0 mm) showed a significant result to 0.04g/mL of A. sativum (14mm) at p = 0.0049 and a higher inhibition index to 0.08g/mL of P. guajava. Inhibition by 0.02g/mL of P. guajava (8.8mm) was advanced than 0.04g/mL of A. sativum (6.3 mm) on S. aureus. Recommendable inhibition of 29.3 mm and 24.0 mm on E. coli 0157:H7 and S. aureus, respectively, were expressed by 0.08 g/mL Z. officinale, which was significant to the standard 0.04 g/mL of Neomycin (Positive control) at p = 0.0067. This study indicated a reliable antibacterial activity by Z. officinale than A. sativum and P. guajava, which might have been due to the high concentration of alkaloids and flavonoids. Nevertheless, A. sativum, P. guajava, and Z. officinale are normally used as fruit and food additives in the human diet, thus can be combined to prevent food poisoning by E. coli 0157:H7 and S. aureus and their exotoxins.
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    Forecasting Commodity Price Index of Food and Beverages in Kenya Using Seasonal Autoregressive Integrated Moving Average (SARIMA) Models
    (EJ-MATH, European Journal of Mathematics and Statistics, 2021-12-01) Wagala, Adolphus; Muriithi , Dennis K.
    Price stability is the primary monetary policy objective in any economy since it protects the interests of both consumers and producers. As a result, forecasting is a common practice and a vital aspect of monetary policymaking. Future predictions guide monetary and fiscal policy tools that that be used to stabilize commodity prices. As a result, developing an accurate and precise forecasting model is critical. The current study fitted and forecasted the food and beverages price index (FBPI) in Kenya using seasonal autoregressive integrated moving average (SARIMA) models. Unlike other ARIMA models like the autoregressive (AR), Moving Average (MA), and non-seasonal ARMA models, the SARIMA model accounts for the seasonal component in a given time series data better forecasts. The study relied on secondary data obtained from the KNBS website on monthly food and beverage price index in Kenya from January 1991 to February 2020. R-statistical software was used to analyze the data. The parameter estimation was done using the Maximum Likelihood Estimation method. Competing SARIMA models were compared using the Mean Absolute Error (MAE), Mean Absolute Scaled Error (MASE),.and Mean Absolute Percentage Error (MAPE). A first-order differenced SARIMA (1,1,1) (0,1,1)12 minimized these model evaluation criteria (AIC = 1818.15, BIC =1833.40). The forecasting ability evaluation statistics MAE = 2.00%, MAPE = 1.62% and MASE = 0.87%. The 24-step ahead forecasts showed that the FPBI is unstable with an overall increasing trend. Therefore, the monetary policy committee ought to control inflation through monetary or fiscal policy, strengthening food security and trade liberalization.
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    Singular Spectrum Analysis: An Application to Kenya’s Industrial Inputs Price Index
    (EJ-MATH, European Journal of Mathematics and Statistics, 2022-01-07) Wagala, Adolphus; Kimutai , Emmanuel K.
    Time series modeling and forecasting techniques serve as gauging tools to understand the time-related properties of a given time series and its future course. Most financial and economic time series data do not meet the restrictive assumptions of normality, linearity, and stationarity of the observed data, limiting the application of classical models without data transformation. As non-parametric methods, Singular Spectrum Analysis (SSA) is data adaptive; hence do not necessarily consider these restrictive assumptions as in classical methods. The current study employed a longitudinal research design to evaluate how SSA fist Kenya’s monthly industrial inputs price index from January 1992 to April 2022. Since 2018, reducing the costs of industrial inputs has been one of Kenya’s manufacturing agendas to level the playing field and foster Kenya’s manufacturing sector. It was expected that Kenya’s Manufacturing Value Added hit a tune of 22% by 2022. The study results showed that the SSA (L = 12, r =7) (MAPE = 0.707%) provides more reliable forecasts. The 24-period forecasts showed that the industrial inputs price index remains high above the index in 2017 before the post-industrial agenda targeting a reduction in the cost of industrial inputs. Thus, the industrial input prices should be reduced to a sustainable level
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    Evaluating the Predictive Ability of Seasonal Autoregressive Integrated Moving Average (SARIMA) Models When Applied to Food and Beverages Price Index in Kenya
    (EJ-MATH, European Journal of Mathematics and Statistics, 2022-04-08) Wagala, Adolphus; Wanjuki, Teddy M.
    Price instability has been a major concern in most economies. Kenya's commodity markets have been characterized by high price volatility affecting investment and consumer behaviour due to uncertainty on future prices. Therefore, precise forecasting models can help consumers plan for their expenditure and government policymakers formulate price control measures. Due to the seasonality of Kenya's food and beverage price indices, the current study postulates that the Seasonal Autoregressive Integrated Moving Average (SARIMA) model can best be the best fit model for the data. The study used secondary data on Kenya's monthly food and beverage prices index from January 1991 to February 2020 to examine the predictive ability of the possible SARIMA models based on the minimisation of the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). A first-order differenced SARIMA (1,1,1) (0,1,1)12 minimized these model evaluation criteria (AIC = 1818.15, BIC =1833.40). The cross validation test results of 6, 12, 18, 24, 30, and 36 step-ahead forecasts demonstrated that SARIMA models are unstable for use in forecasting over a long-time period with a tendency of increasing prediction errors with an increase in the forecast period. It is anticipated that the findings of the current study will provide necessary valuable information to the policymakers and stakeholders to understand future trends in commodity price.
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    Characterization of culturable microbial community in oil contaminated soils in Greater Port Harcourt Area, Nigeria
    (Academic Journals, 2020-09-17) Wanjala , Muyoma Paul
    The study investigated microbial population dynamics in soils of Greater Port Harcourt Area, Nigeria. The study involved the quantification of petroleum pollutants and the enumeration and characterization of culturable fungi and bacteria. Gas Chromatograph FID method was used to quantify total petroleum hydrocarbons (TPH) in the soil while morphological and biochemical tests were used to characterize the microorganisms. The highest TPH was 9,759.37±883.36 ppm which exceeded the Department of Petroleum Resources’ (DPRs’) intervention value of 5,000 ppm. The percentage of hydrocarbon utilizing fungi (% HUF) ranged between 1.93±0.57 and 66.55±5.60 which were observed in sites A1 (Aluu) and CA (Agricultural control), respectively. The percentage of hydrocarbon utilizing bacteria (% HUB) ranged between 0.12±0.01 and 7.89±1.25 which was observed in sites A3 (Emuoha) and CU (Urban control), respectively. The most prevalent bacterial species includes Bacillus subtilis, Micrococcus lylae, Staphylococcus aureus, Bacillus cereus and Alcaligen faecalis. The most prevalent HUB isolate was Bacillus subtilis. The most prevalent fungal isolates were Aspergillus niger, Aspergillus flavus and Candida torulopsis. A. niger was the most prevalent among the HUF isolates which was identified in 12 sites. It was concluded that the study sites harboured TPH degrading microorganisms that are appropriate for bioremediation of TPH polluted sites.
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    Impact of Nitrogen Fertilizer Use on Soil Ecosystem Integrity in the Greater Port Harcourt Region, Nigeria
    (Science Publishing Group, 2021-10-05) Wanjala , Muyoma Paul
    Fertilizers are used to increase crop yields in agriculture but can affect the integrity of soil ecosystems if misused. The present study was conducted to observe the impact of inorganic fertilizers in selected soils in Greater Port Harcourt Area on soil microbial population, in addition, the association between soil microbial population and Lethal Concentration 50 (LC50) was observed. Microbial communities and LC50 values were determined using normal analytical procedures. The study showed various fertilizer types that altered soil microbial population and LC50 values. For agricultural areas the maximum NPKB mean value was 0.70±0.76 ppm which was higher than the mean value of the control location of 0.23±0.00 ppm. Urea tolerant fungi’s (UREAF's) LC50 mean value was 0.43±0.09 ppm in the agricultural area as compared to the control with a mean value of 0.46±0.00 ppm. Industrial and urban areas had significantly different mean values of 0.29 ± 0.19 ppm and 0.18±0.01 ppm and 0.23 ± 0.06 ppm and 0.23 ± 0.060.17 ± 0.010.17 ± 0.010.17 ± 0.01 ppm respectively (p = 0.001). This research concluded that the application of UREA and NPK fertilizers in study area soils lowered the pH of soils in A1, A2 and A3 agricultural sites. Application of UREA and NPK fertilizers in soils of the study areas increased the population of microorganisms in threshold concentrations but was detrimental for NPK and UREA fertilizers at concentrations of 1.50% or above. Further findings showed that microorganisms were more tolerant of NPK and UREA fertilizers in agricultural areas compared to urban and industrial areas which showed higher LC50 values. This research concludes that fertilizers used in the study areas were related to soil microorganisms developing tolerance to NPK and UREA. Farmers should observe application of the recommended professional quantities of fertilizers to ensure the sustenance of the soil ecosystem integrity.
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    Characterization of Chemically Activated Carbons Produced from Coconut and Palm Kernel Shells Using SEM and FTIR Analyses
    (Science Publishing Group, 2021-06-30) Wanjala , Paul Muyoma
    Chemically activated carbons generated from coconut (CS) and palm kernel (PKS) shells soaked with 1M solution of K2CO3 and NaHCO3 at 1000°C using the Carbolite Muffle Furnace were examined using scanning electron microscopy (SEM) and Fourier Transformation Infrared Spectroscopy (FTIR). Results from the FTIR analyses revealed that the coconut and palm kernel shells manufactured were successfully chemically activated. Several chemical compounds and functional groups, such as hydroxyl groups, carbonyl groups, ethers, alkanes, alkenes, and aromatic groups, were detected in chemically activated carbon produced from palm kernels and coconut shells as proof of the lignocellulose structure in them. Chemically activated carbon made from coconut shells exhibited nine distinct spectra, while palm kernel shells exhibited six distinct spectra. The pores were larger in the chemically activated carbons produced at a higher temperature (1000°C), demonstrating that temperature is an essential process parameter in the development of surface porosity in chemically activated carbons. The chemical carbonization activation methods used provided porosity, a large surface area, and precise morphology for absorption in both the coconut and palm kernel shells, indicating that they can be turned to high-performance adsorbents. Both organic and inorganic contaminants can be removed from the environment using the chemically activated carbons produced.
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    Evaluation of the Effects of Cadmium in Soil on the LC50 of Soil Bacteria and Fungi for Environmental Monitoring
    (J. Appl. Sci. Environ. Manage., 2021-05-07) WANJALA, MP;
    Contamination of soil with heavy metals by is currently of global concern. Cadmium (Cd) is one of the metals of concern. In the current study, LC50 of Cd to soil bacteria and fungi was used to assess the impact of anthropogenic activity in development of Cd tolerance in soil microorganisms. Levels of Bio-physicochemical parameters in soil were determined. Results show that the concentration of Total Petroleum Hydrocarbon (TPH) and Cd in soil ranged between 5.09±0.33 to 9261.94±287.67, and 0.023±0.015 to 0.057±0.012 ppm respectively. There was significant difference (p = 0.001) in LC50 for fungi between the study and control samples. Pearson correlation showed that there was significant relationship (r = 0.30) between LC50 for bacteria and TPH. There was significant difference (p = 0.017) in LC50 values among the study and control samples for fungi. Anthropogenic activities influenced the concentrations of TPH soil but did not influence levels of Cd.
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    Assessment of Ni Toxicity to Fungi and Bacteria in Oil Tainted Soils in Greater Port Harcourt Area, Nigeria
    (J. Appl. Sci. Environ. Manage., 2021-07-01) Wanjala M. P, et al.
    Intensified urbanization and industrialization are rapidly triggering the release of pollutants to the environment. This study determined the extent of soil contamination with Nickel (Ni) in oil mining areas and its effect on the levels of Ni tolerance by fungi and bacteria. The total CFUs/g of soil were enumerated after a culture period of 7 days at 28°C and LC50 was determined using probit and regression analysis. The mean values of Ni were 1.38±0.23 in industrial area, 1.41±0.36 ppm in agricultural area and 1.02±0.64 in urban area. The mean values of Total Petroleum Hydrocarbon (TPH) were 4,405.46 ppm in industrial area, 55.65 ppm in agricultural area and 1,304.53 ppm in urban area. Nickel’s peak concentration indicating growth of both fungi and bacteria at 150 ppm. There was significant difference (p ≤ 0.000) in the mean levels of LC50 for fungi among the study sites. There was no significant correlation between the concentration of TPH in soil and LC50 of fungi (r = -0.169) and bacteria (r = 0.042). In conclusion, TPH influenced the levels of fungi and bacteria tolerance to Ni in soils. Moreover, it was observed that LC50 can be a reliable method for monitoring chemically resistant microorganisms directly in the environment to improve the use of microorganisms for the bioremediation of oil contaminated soils and in monitoring of antibiotic resistant microorganisms in natural ecosystems
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    (International Journal of Advanced Research in Management and Social Sciences, 2015-06) Orwa, George O.; Kariuki, Samuel Nduati; Namusonge, Gregory S.
    Cash is an important requirement to ensure continued operations, yet excessive cash holdings might result in many problems which include; higher opportunity costs of holding cash, cash abuse, a tool for obtaining the controlled self-interests and the higher agency costs. The study established thatthere is a negative and insignificant linear relationship between growth opportunities and corporate cash holdings. The study also revealed that leverage is a significant positive determinant of corporate cash holdings in line with the precautionary motive. In regard to firm size, the study findings indicate that firm size positively determines corporate cash holding. Further, the study revealed that there is a negative linear relationship between likelihood of financial distress and cash holdings.The findings also confirmed a positive relationship between cash flow variability and corporate cash holdings.The study therefore concludes that; leverage, firm size, likelihood of financial distress and cash flow variability determine corporate cash holdings among private manufacturing firms in Kenya