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A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Hydrology and Water Resources Engineering of the Nelson Mandela African Institution of Science and Technology
(NM-AIST, 2025-07) Zakaria,Onesmo
The world over, water resources availability is in decline while population and associated water
demands are in an increase. This limits the capacity of hydrologic catchments to sustain the
growing economic activities. In this regard, the productivity value of water (PVW) is
increasingly gaining popularity among water resources managers as a tool for water allocation.
Studies on PVW help to complete the Integrated Water Resources Management Pillars i.e., the
famous 3E’s (Equity, Economic/Efficiency and Ecological Integrity) by assessing the value of
water beyond just the equity principle that only concentrates on the fair volumetric share of
water. However, PVW concept is at its nascent stage characterized by a lack of a knowledge
and tools to relate water resources and the economy it propels. The current study therefore,
began by assessing catchment hydrologic carrying capacity and delved into assessing PVW
after which a marginal productivity of water (MPW) was assessed to determine increasing or
diminishing return for every change in water use. These were preceded by an analysis of
hydrologic carrying capacity of the catchment where non-parametric Mann-Kendall (MK)
statistical tests as well as the Soil and Water Assessment Tool (SWAT) were applied. These
helped to assess climate trend and model the interaction of hydrology, climate and land
use/cover changes and their implication to water availability. The results showed that the
historical hydrologic parameters were favorable whereas the future painted a stressful scenario
(p<0.05). Given the increased expansion of thirsty sectors of economy, the seemingly
increasing river discharge at Swero (1KB17) gauging station was attributed to sediment
deposition with annual loos of 42.13 Tonnes/Ha in 2021 to a projected sediment loss of 43.95
Tonnes/Ha in 2041. Furthermore, findings on productivity of water showed that paddy had low
PVW (0.01 USD/m3) compare to Sugarcan (0.10 USD/m3) and Hydroelectric production (0.19
USD/m3). However, the sub-sector is the most impactful in terms of food and employment
security. On these bases, deliberate support and protracted capacity building and advocacy for
the rainfed system of rice intensification (SRI) is recommended as a plausible paddy farming
system which also had good PVW (0.11USD/m3). This study also recommends assessment of
the value of water for the environment as an important sector as well as across the value chain
for all sectors. Finally, the study recommends improvements in enforcing both water and LULC
plans to ensure controlled expansion of economic activities that sustains the catchment performance.
A Project report Submitted in Partial Fulfilment of the Requirements for the Degree of (Master’s in Health Physics and Radiation Protection) of the Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania
(NM-AIST, 2025-04) Moses,Omega
High-dose-rate intracavitary brachytherapy is a crucial part of cervical cancer treatment, delivering high doses to the tumor while minimizing exposure to normal tissues. However, improper administration can lead to radiation-induced damage. In vivo dosimetry is essential for verifying that the planned treatment dose matches the radiation delivered doses. This study utilized Thermoluminescent dosimeters (TLDs) to measure the radiation dose
delivered to the rectum in two patient groups: one with first fraction-based planning (FFP) and the other with each fraction planned individually (EFP). Applicator and probe positions from the treatment planning system (TPS) were used to assess the shift between treatment fractions. The median dose measured by TLDs (3.85 Gy, IQR = 2.23) exceeded the planned dose by TPS (3.37 Gy, IQR = 1.54), with a p-value < 0.001. The interquartile range (IQR) of dose difference
was higher in the second fraction, 1.92 Gy, in the FFP group, and the dose differences between the first and second fractions were not statistically significantly different for either group. The applicator position shows a minimal shift between the first and second fraction compared to a rectal probe. Generally, it is best practice to plan each fraction independently to minimize potential risks. In scenarios such as when patients are transferred from a brachytherapy couch to a stretcher, separate imaging and planning each fraction is not necessary.
A Thesis Submitted in Fulfilment of the Requirements for the Award of the Degree of Doctor of Philosophy in Materials Science and Engineering at Nelson Mandela African Institution of Science and Technology
(NM-AIST, 2025-07) Sufiani,Omari
This study reports on the synthesis, characterization and application of sodium superionic conductors for water desalination by Capacitive deionization (CDI).The Sodium super ionic conductors (NASICONs) outperform carbon-based adsorbents and most battery electrodes due to their 3D bulk ion storage, exceptional ionic conductivity and strong structural stability.Variable synthesis conditions were applied namely the number of sulphate ions substituted for
phosphates in Na3Fe2(PO4)3 (NFP) and mass ratios of activated carbon (AC)/NFP to prepare NaFe2PO4(SO4)2/C (NFPS/C) and AC/NFP composites respectively. Several characterization techniques such as X-ray diffraction, scanning electron microscopy, Transmission electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption-desorption measurements and X-ray photoelectron spectroscope confirmed the synthesized materials. Characterization results show that the N2 adsorption-desorption isotherms of AC/NFP composite is of type III, suggesting slit shaped pores due to accumulation of flake shaped particles. The X-ray diffraction analysis revealed NFPS/C to exhibit orthorhombic structure while AC/NFP had monoclinic crystal system. The scanning electron micrographs revealed the particles of both NFPS/C and AC/NFP composite less aggregated. Due to less aggregated particles of NFPS/C observed in SEM micrographs it was used in CDI wherein, the salt removal capacity increases with the solution concentration, desalination duration and applied potential. Further, experiments involved desalination of Indian Ocean water solutions diluted several times to achieve the concentration of solution resembling permeates produced by seawater reverse osmosis (SWRO) which is attained by water samples diluted one hundred times (487 µS/cm). The salt removal capacity for desalination of Indian Ocean water samples not diluted and diluted hundred times was about 27.3 and 10.6 mg/g, respectively. Further CDI tests involved comparing the salt removal capacity of the AC and AC/NFP composites wherein, much higher performance of around 22.0 was attained by AC/NFP 1:2 against 18.65 mg/g of AC. The improved performance of AC/NFP 1:2 composite might be due to its high specific surface area and the enhanced interfacial contact between the composite and the salt solution. These results demonstrate that NASICONs present a viable strategy for improving desalination efficiency of a CDI system.
A Dissertation Submitted in Partial Fulfilment of the Requirements for the Award of the Degree of Doctor of Philosophy in Materials Science and Engineering of the Nelson Mandela African Institution of Science and Technology
(NM-AIST, 2025-07) Malashi,Nyanda
Dye-sensitized solar cells (DSSCs) are promising third-generation photovoltaic cell technology
due to their easy fabrication and environmental friendliness. In DSSCs, a photosensitizer is
crucial for photon absorption, and electron transfer. Natural pigments are investigated as
photosensitizers in DSSCs due to their abundance and environmental friendliness. However,
their narrow solar spectrum absorption and weak bonding with the semiconductor limit their
wide application, necessitating the design of novel photosensitizers. This work focuses on the
theoretical design of Braz-Bd-ether, Braze-Bd-ether, Aliz-Bd-ether, Braz-Bd-oxane, Aliz-Bd
oxane, Quinaliz-Bd- oxane molecules via etherification and bi-etherification reactions.
Moreover, Braz 01, Braz 01b, Braz 01t, Braz 01tb, Braz 02, Braz 02b, Braz 02t and Braz 02tb
molecules were obtained from the chemical structure modification of brazilin dye. The
photoelectrical, optoelectronic and structural properties of the isolated dye, dye@(TiO2)9H4
and dye@I2, were examined using DFT and TD-DFT methods. The DSSCs’ performance was
simulated using TiberCAD software. The results reveal that Braz-Bd-oxane, Braze-Bd-ether,
Aliz-Bd-ether, Aliz-Bd-oxane and Quinaliz-Bd-oxane complexes exhibited improved non
linear optical properties (NLO), reduced energy gap, lower exciton binding energy (Eb), lower
total reorganization energy (λt), and red-shifted absorption spectra by 10.29 nm ‒ 54.83 nm
regarding betanidin dye. The frontier molecular orbital (FMO) plots, ∆Ginj (-0.248 ‒ -0.453
eV), ΔGreg, and energy level alignment plots indicate that all designed complex dyes inject
electrons into TiO2 and are regenerated by I‒/I3‒ redox electrolyte, satisfying the photosensitizer
requirement. For Braz 01-Braz 02tb, are predicted to have improved charge transfer due to
reduced λtotal (0.951 eV ‒ 0.528 eV), increased EA (1.021 ‒ 3.472 eV), and decreased IP (5.591
5.252 eV). Additionally, the designed dyes (Braz01‒Braz02 tb) exhibited high current density
and minimal charge recombination compared to the brazilin dye, attributed to their red-shifted
absorption spectra, reduced Eg (5.074‒2.46 eV) and Eb (0.591‒0.137 eV). Negative Eads for the
dyes@(TiO2)9H4 and dye@I2 were noticed for all dyes, signifying spontaneous chemisorption
adsorption. Moreover, the 1D-DSSCs sensitized with designed complex dyes exhibit greater
power conversion efficiency (PCE) than natural dyes forming these complexes. Aliz-Bd-oxane
and Braz-Bd-oxane exhibited higher PCEs of 14.78% and 14.74% among the designed
complexes. Also, Braz 01-Braz 02tb demonstrated higher PCE than brazilin dye. The 1D
DSSC-Braz 01tb dye has the highest PCE of 13.44%. Therefore, the designed molecules Braz
Bd-oxane, Aliz-Bd-oxane, Braze-Bd-ether, and Braz 01tb are better photosensitizers in DSSC.
A Dissertation Submitted in Partial Fulfilment of the Requirements for the Degree of Master of Science in Sustainable Energy Science and Engineering of the Nelson Mandela African Institution of Science and Technology
(NM-AIST, 2025-06) Mbugano, Milton
Storage of vaccines and perishable food in regions without access to the national grid electricity presents ongoing challenges, especially in remote regions. Solar-powered system offers a reliable and sustainable alternative. This study presents a techno-economic analysis (TEA) and life cycle assessment (LCA) of a locally developed solar-powered cooler designed for such conditions. The cooler serves as a lower-cost alternative to conventional electric-powered refrigeration units, especially where grid access is unreliable or unavailable. The analysis was
performed using ReCiPe2016 midpoint indicators with SimaPro software and Microsoft Excel 2019 to assess both environmental and economic factors. Results from the LCA show that battery production contributes the most toenvironmental impacts, followed by solar panel. Terrestrial ecotoxicity was the highest environmental concern, with human non-carcinogenic toxicity also notable. The TEA indicates strong economic performance, with an initial investment of USD 2682, a payback period of one year, and a return on investment of 98.8%.
These results support the cooler’s potential for use in off-grid health and food supply chains. These quantitative analyses provide valuable insights for decision-makers, aiding in understanding both economic aspects and environmental impacts throughout the life cycle of locally manufactured solar-powered coolers, thereby enhancing their sustainability.