Ethiopian Journal of Science and Technology

Mathematical analysis of in-host Ebola virus infection dynamics model with sensitivity analysis

Seleman Ismail — 2023-12-25

Ebola virus (EBOV) causes a haemorrhagic and lethal Ebola disease disastrous to human beings, which is transmitted by contact of body fluids of infected animals and humans. Presently, there are no therapies for the disease. In this paper, a mathematical model is proposed to investigate the in-vivo dynamics of EBOV infection with sensitivity analysis. A system of five non-linear ordinary differential equations constitutes the model, from which the basic reproduction number, R₀ is calculated using the next generation matrix method. The parameter R₀ is employed to analyze global stability of disease-free and endemic equilibria. Using the Metzler matrix operator, the results indicate that the disease-free equilibrium point is globally asymptotically stable provided that R₀ < 1, which implies that the disease disappears from the host after some period of time. With Lyapunov Stability Theory and LaSalle Invariant Principle, the results indicate that the endemic equilibrium point is globally asymptotically stable provided that R₀> 1, which implies that the disease persists in the host. Sensitivity analysis of the basic reproduction number pertaining to the model parameters is achieved using forward normalized sensitivity index method. The results indicate that the parameters for infection rate, production rate of uninfected target cells and virus replication rate are positively sensitive. On the other hand, the parameters for natural death rate of target cells and natural death rate of the virus are negatively sensitive, implying that the basic reproduction number decreases as the parameters increase and vice versa. Besides, it is shown that the parameter for the infection rate is the most sensitive one while the parameter for the virus reproduction rate is the least sensitive one. Numerical simulations are used to validate the analytical results. The results suggest implementation of deliberate control measures to eradicate EBOV disease by considering sites in the model to which the most sensitive parameters are affiliated.

Silver nanoparticles incorporated local montmorillonite clay modified carbon paste electrode for the voltammetric determination of Arsenic (III) in aqueous solution

Mekonnen Mihiret Dessie — 2023-12-25

A sensitive electrochemical method was developed to determine arsenic (III) using silver nanoparticles incorporated local montmorillonite clay nanocomposites modified carbon paste electrode (Ag-NPs/MT/CPE) in aqueous solution. Electrochemical properties of carbon paste electrode (CPE) modified by Ag-NPs/MT nanocomposite were studied using cyclic voltammetry and electrochemical impedance spectroscopy in the presence of 10 mM K₃Fe(CN)₆^3-/4-/0.1 M KCl aqueous solution as well as in the presence of 100 μg/mL As (III) in 0.1 M PBS. Voltammograms acquired on Ag-NPs/MT/CPE showed an enhancement of the oxidation current density peak compared to the bare CPE. This is attributed mainly to the catalytic activity and improved surface to volume ratio of Ag-NPs/MT composite. The electrochemical sensor based on Ag-NPs/MT nanocomposite was constructed and used for the detection of As (III). Under optimized condition (pH 7, deposition potential-0.3 V and deposition time 60 s) the sensor exhibits sensitivity 0.02953µA/µg/mL and detection limit 38.2 µg/mL As (III). The Ag-NPs/MT/CPE has also shown good stability, it retained a response of 93.8% of the initial current after 12 days storage at room temperature. Therefore, the developed sensor can be a good candidate for electrochemical determination of As (III) in aqueous solution.

Association of traits in potato (Solanum tuberosum L.) cultivars evaluated in Central Ethiopia

Lemma Tessema — 2023-12-25

Knowledge of the magnitude of traits association helps to determine the relative contribution of traits toward yield and other important characteristics in crop breeding programs. The present study was conducted on twenty improved varieties and one local farmers` potato cultivar at two different sites in the Central Highlands of Ethiopia under rain-fed conditions in the main cropping season of 2017 to estimate association among traits using a randomized complete block design with three replications. Analysis of variance for each location and over locations revealed the presence of highly significant (p < 0.01) differences among varieties for studied traits. Plant height, stem number per hill, average tuber number per hill, average tuber weight, and total starch yield showed positive and significant correlations with total tuber yield at both genotypic and phenotypic levels. Average tuber number per hill, average tuber weight and total starch yield had positive and direct effects on total tuber yield at the genotypic level whereas, plant height, stem number per hill, average tuber number per hill, average tuber weight, total starch yield exerted indirect effects on total tuber yield through other traits. Hence, traits that exerted positive and direct effects on total tuber yield at the genotypic level could be considered as selection criteria in future potato breeding programs considering further comprehensive study by including more potato varieties and local cultivars across wider production environments.

The synthesis and characterization of the two 2-(tert-butyl) cyclohexyl methanesulfonate compounds

Lewis Mtashobya — 2023-12-25

This short communication reports the synthesis and characterization of the mixture of two diastereoisomeric methanesulfonate compounds, 2-(tert-butyl) cyclohexyl methanesulfonate. Methanesulfonate group was introduced into the compounds due to its effectiveness as a protecting and good leaving group in nucleophilic substitution reactions. These intermediate compounds were prepared in an attempt to introduce fluorine at position two of the two target diastereoisomeric fluorinated compounds 1-(tert-butyl)-2-fluorocyclohexane which are important for studying the properties of hydrogen bond in fluorinated compounds. The two methanesulfonate compounds were formed as an inseparable mixture in 23% yield through alkylation with methanesulfonyl chloride and were characterized and identified by the ¹H NMR and ¹³C NMR spectroscope. The compounds are reported as useful substrates in nucleophilic substitution reactions due to their effectiveness as leaving groups.

Thermochemical conversion of underutilized lignocellulosic waste to syngas: Supercritical water gasification for value addition to corncob and sisal waste

Datius S. Revocatus — 2023-12-25

In the context of escalating global energy demands and environmental concerns associated with fossil fuels, this paper reports the conversion of underutilized agricultural residues in Tanzania, namely corncob and sisal waste, into syngas as sustainable biomass alternatives for energy production. Employing supercritical water gasification, the study evaluated the potential of corncob and sisal waste for syngas generation. Proximate analysis showed corncob as more suitable for energy conversion due to its lower moisture content (11.5%) and higher volatile matter (74.9%), compared to the higher moisture (14.9%) and ash content (17.2%) of sisal waste. However, the elemental analysis underscores both materials' feasibility for syngas production, with corncob and sisal waste showing substantial carbon and hydrogen contents, which are crucial for syngas. Despite the slight energy advantage of corncob indicated by its higher heating values (HHV: 25.44 MJ/kg, LHV: 24.40 MJ/kg) over sisal waste (HHV: 24.87 MJ/kg, LHV: 23.86 MJ/kg), reaction kinetics and syngas composition analysis suggested that both residues are viable feedstocks. Reaction kinetics analysis revealed temperature dependence in the conversion process, with higher temperatures favoring hydrogen production but increasing CO₂ emissions, underscoring the need for a balanced approach in syngas production. The syngas produced composes of H₂, CO, CH₄, CO₂, and light hydrocarbon gases. Moreover, the H₂/CO of the syngas gas was less than 1, suggesting that this syngas would be suitable for oxo-synthesis, aligning with existing literature. Regression analysis highlights temperature as the most influential factor on Total Syngas Yield, with significant R-square values (0.992 for corncob and 0.944 for sisal waste). However, a paired sample T-test indicated no significant yield difference between corncob and sisal waste (t-value = -0.518, p-value = 0.626). These values implied that both feedstocks are equally effective in syngas production under the examined conditions. This observation suggested that feedstock selection can be flexible based on other factors such as availability and environmental impact. The findings contribute new insights into biomass-to-energy conversion, emphasizing the viability of agricultural residues as sustainable energy sources. It informs feedstock selection, balancing environmental impact and cost factors, and advocates for a shift towards a more sustainable, circular energy economy.