School of Physical Sciences (Phys-Sciences) Collections
Permanent URI for this collection
Browse
Recent Submissions
1 - 5 of 250
-
ItemA mathematical model for COVID-19 transmission dynamics in a population with treated and untreated type 2 diabetes(Makerere University, 2026)The COVID-19 disease posed critical challenges to global health, particularly among individuals with pre-existing conditions such as Type 2 diabetes. While evidence suggested that Type 2 diabetes worsened COVID-19 outcomes, the e ect of Type 2 diabetes treatment on the disease dynamics remained unclear. This study formulates and analyzes a deterministic SEIR mathematical model of COVID-19 transmission in a population with and without Type 2 diabetes, subdividing diabetics into untreated and treated groups. The study derives the basic reproduction number (R), assesses equilibrium stability, and conducts sensitivity analysis to identify key parameters that in uence infection dynamics. Numerical simulations indicate that treatment of Type 2 diabetes reduces the infectious diabetic population, increases recovery, and lowers the basic reproduction number under appropriate parameter values.
-
ItemHydrogeological characterization of the groundwater resources in Lwengo District, Central Uganda.(Makerere University, 2026)This study presents a hydrogeological characterization of groundwater resources in Lwengo District, Central Uganda, focusing on aquifer properties, groundwater flow dynamics, hydrochemical composition and the factors influencing groundwater recharge using secondary datasets from the Directorate of Water Resources Management (DWRM/MWE), including borehole logs, aquifer test reports, topographical information and hydrochemical datasets. Aquifer parameters were estimated from four long-duration pumping tests using the Theis (1935) and Cooper-Jacob (1946) methods, while hydrochemical analyses were used to classify groundwater types and identify controlling geochemical processes. Results indicate that groundwater occurs mainly within weathered and fractured crystalline basement rocks under confined to semi-confined conditions. Water bearing zones occur at depths of 22–50 m below ground level, with static water levels ranging from 8–20 m. Aquifer parameters indicate low to moderate productivity, with transmissivity values of 0.3–5.5 m²/day, hydraulic conductivity of 0.02–0.2 m/day and storativity ranging from 2 × 10⁻⁵ to 1 × 10⁻⁴. Groundwater recharge is influenced by rainfall, topography, land use and the weathered and fractured basement geology, resulting in spatial variability across the district. Groundwater is predominantly characterized by Ca-Mg-HCO₃ and Ca-Mg-SO₄-Cl facies, controlled mainly by rock–water interaction and silicate weathering. Moderate mineralization was observed, while elevated nitrate and phosphate concentrations in some boreholes suggest localized agricultural and sanitation impacts. The findings demonstrate that groundwater occurrence in Lwengo District is structurally controlled and spatially heterogeneous, highlighting the importance of integrating geological, structural, geophysical, recharge and water quality assessments for sustainable groundwater resource development and management.
-
ItemA statistical comparison of finite Time Lyapunov exponents and Okubbo-Weiss parameter(Makerere University, 2026)In this study, we have investigated stirring and mixing properties of particle transport by analyzing the statistical moments from PDFs of Okubbo-Weiss (OW) or Finite time lyapunov exponet (FTLE) diagnostics. In contrast with OW metric, FTLE tools have the advantage of exploiting both spatial and temporal variability of the velocity field and are in principle able to unveil subgrid filaments generated by chaotic stirring. However, one may wonder whether why this statistical advantage is of practical interest in real-data, mesoscale and sub-mesoscale analysis, because of the uncertainties from resolution and binning of data. Here we have compared the ability of OW and the FTLE statistics in detecting transport and mixing properties in fluid flows. By considering two examples of geophysical interest the meandering jet flow and ABC steady flow, we found that the two approaches provide similar results for slowly evolving vortices at early times. However, the FTLE was also able to predict the filamentary processes. Such filaments were also observed, with some mismatch in the two velocity fields, didn’t show any compact relation with other OW diagnostic. It has been found that the OW is a limiting case of the FTLE, Probability distribution functions (PDFs) of FTLEs and OW are computed to better understand implications for mixing and stirring. The study of the shape of the PDFs and their sensitivity, or lack thereof, to whether the FTLE or OW is computed based on 2D or 3D flows allowed us to make inferences about the nature of mixing and stirring. The probability distribution functions (PDFs) are found to be non Gaussian. The nonGaussianity of these PDFs suggests that parameterization schemes in existing numerical models should be improved.
-
ItemAssessment of pesticide residues from herbal medicines sold in selected markets in Kampala District, Uganda(Makerere University, 2025)The growing reliance on herbal medicines in Uganda, especially in Kampala District's urban areas, has raised safety concerns due to potential pesticide contamination. This study evaluated pesticide residue levels in herbal medicines sold in four major markets (Kalerwe, Usafi, Owino, and Nakasero) in Kampala District and evaluated the associated health risks through consumption of pesticide-contaminated herbal medicines. A total of 64 herbal medicine samples (48 liquid and 16 solid formulations) were analysed. Samples were extracted using solvent-based techniques (acetonitrile for liquids and a mixture of n-hexane/dichloromethane for solids), cleaned with Florisil-packed columns, and analyzed using gas chromatography-mass spectrometry (GC-MS) for 31 pesticides of various chemical groups (organochlorines, OCPs; organophosphates, OPPs; herbicides; other pesticides, namely cypermethrin, quinoxyfen, and cybutryne). Pesticide levels in liquid samples ranged from 1.20 to 306.07µg kg⁻¹ f.w., with the total mean of 96.89 µg kg⁻¹ f.w. OCPs were the most predominant pesticides (45.1% of the total pesticides), followed by others (23.2%). For solid samples, pesticide concentrations varied from 0.36 to 307.34 µg kg⁻¹ d.w., with the total mean of 162.11 µg kg⁻¹ d.w. The herbal medicines from Nakasero market had the highest total mean concentrations (148.9 µg kg⁻¹), followed by Owino (112.60 µg kg⁻¹). Endrin-aldehyde was the most frequently detected pesticide (98.4% of the samples), while hexachlorobenzene was the least detected (14.1%). In general, the pesticide levels were below the limits set by the World Health Organization (WHO), Food and Agriculture Organization (FAO), and Codex Alimentarius Commission for herbal products. Most of the samples had HQ and HI values
-
ItemImpact of depositional architecture on petroleum reservoir quality of South Lake Albert Basin, Western Uganda(Makerere University, 2026)Depositional environments and architectures’ interpretations and analyses were carried out in the South Lake Albert Basin to map out depositional environments and their associated architectures with the main objective of establishing the impact of depositional architecture on the petroleum reservoir quality within the stratigraphic section, Late Miocene to Late Pliocene stratigraphic interval (11.6 ma to 5.3 ma). Structural modelling was conducted to generate depth structural maps to guide the development of zoned models. In addition, facies and petroleum reservoir property modelling, geological sampling and stratigraphic logging were undertaken to evaluate petroleum reservoir properties and depositional environments with their associated architectures. Thin section analysis was conducted on cored and field samples to investigate spatial and stratigraphic distribution of porosity and permeability. The results indicate that South Lake Albert Basin is comprised of structural compartments, pinchouts, flower structures, folds, a fault that makes a terrace in the basin, and a basin bounding fault in the Kaiso-Tonya area, normal faults with limited displacements and a basin bounding fault in the Kingfisher area. Sediments were also found to be highly intercalated. Alluvial fans, fluvial, deltaic and lacustrine depositional environments with associated depositional architectures are found. Petroleum reservoir quality in both Kaiso-Tonya and Kingfisher areas was found to be very low to high. Sections that are close to the basin bounding fault for both Kaiso-Tonya and Kingfisher areas consist of alluvial fan and fluvial depositional environments and have low to moderate petroleum reservoir quality. The section that is close to the lake and under the lake consists of deltaic and lacustrine depositional environments and has moderate to high petroleum reservoir quality. The results found that compartmentalization, pinchouts and intercalations and facies heterogeneity of sediments, and all other identified architectural elements influence the petroleum reservoir quality. They found that these identified architectural elements have a high effect on the connectivity, fluid saturation and flow, and delineation/extent of the reservoir continuity. Structural compartments stacked or intercalated sediments, pinchouts lead to reduced connectivity within sediments. They further contribute to the uncertainty in reservoir continuity, stacked petroleum reservoirs with undefined lateral extent and the low to moderate petroleum reservoir quality. The study further developed a petroleum reservoir quality predictive model that will guide future petroleum exploitation programs within the study area and basins with similar sedimentological and structural settings.