Doctoral Theses

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Alizarin-based dyes for dye-sensitized solar cells application
(The University of Dodoma, 2021) Abubakari, Ismail
The advancement in dye-sensitized solar cells technology involves the discovery of new materials with reduced cost and improved performance in terms of solar energy absorption and conversion. This study presents the development of a novel dye molecule based on alizarin for dye-sensitized solar cells. The dye was first designed using Gaussian 09W package before its synthesis. The designing was involving organic compound; alizarin, 4-(benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid, 2-hexylthiophene and carboxylic acid and metals; chromium, iron, copper, zinc and ruthenium to produce organic and organometallic compounds. Different properties including intramolecular charge transfer, absorption properties and photovoltaic properties were analysed to come up with the best dye for synthesis among several dyes designed. Seventeen dye molecules were successful designed with their properties recorded and reported while the best molecule labelled OG3 was successful synthesized as a brownish-orange solid. Together with the synthesized dye, all designed dyes found potential sensitizer in dye-sensitized solar cells with positive outcomes upon electron excitation and injection to semiconductors and successive regeneration by the electrolyte. Moreover, the molecules composed of substituent 2-hexylthiophene were generally better performer compared to others with different substituents. The charge transfer was found spontaneous from the attached groups and unsubstituted ring of alizarin to the substituted rings of alizarin possessing C=O groups. This confirms C=O to be the anchoring groups facilitating binding of dyes to the semiconductor surface hence strengthening the dye-semiconductor interactions. The synthesized dye OG3 was characterized before subjected to photocurrent-photovoltage analysis. Generally, the synthesized dye confirmed to be useful in DSSC applications with short circuit current, open circuit voltage and fill factor of 0.0146 A/cm2, 0.65 V and 0.612, respectively. The conversion efficiency of the cell fabricated using OG3 was found to be 5.81 % under 100 mW/cm2 solar illuminations.
Integration of ethno-fishery into modern fisheries management in Mwanza region Tanzania
(The University of Dodoma, 2017) Rajabu, Abubakar Salum
This thesis presents results of a study which examined local indigenous knowledge and traditional management practices in Kayenze ward in Ilemela, Mwanza Region.The general objective of the study was to investigate and and propose ways to integrate ethno-fishery knowledge into modern fisheries management. More specifically the study examines the extent to which local fishers utilize their knowledge, attitudes and skills in fisheries management. Further the study assesses issues which negatively affect local fishers‟ actions in fisheries. The study also examines strengths, weaknesses, opportunities and threats in fisheries management and lastly it assesses Indigenous Knowledge best practices which can be incorporated into modern fisheries management. A combination of household questionnaires, semi structured interviews with key informants and focus group discussions were used to collect data for the study. The study also reviewed other scientific studies done in the area to validate the survey results. Multinomial regression analysis was used to determine the variables which were important in explaining the amount of variation among respondents on issues partaining to knowledge on identification of plant and animal resources used in fishing activities, attitudes towards conservation of fish resources and their habitats and skills of respondents on making and/or repairing the fishing gadgets. The community in Kayenze have knowledge of various plant and animal resources and their use in fisheries management. In addition, they are able to score the levels of abundance of each species that are directly used in fishing operations. The findings suggest that positive attitude correlates with age. The data suggest that the adult and elders having engaged in fishing activities for many years thus have acquired knowledge for resource conservation and hence have positive attitude. Various skills were observed to follow age categories. Youth were v able to use modern technologies such as welding operation. Adult and elders have skills in tradition, making gadgets like ropes, weaving, knitting and carpentry. The study found that Kayenze inhabitants have developed and maintained some local ecological knowledge and practices that can have significant implications in scientific studies and on the management of Lake Victoria resources. The practices include restricted cutting of water plants in the lake, access and fishing in sacred sites and conservation of water reeds. These traditional practices encouraged regeneration and sustainable utilisation of fish. Local people at Kayenze have sets of seasons for fishing operations observed by the community. This fishing tradition controls fishing activities, preventing fishing during harvest when there is plenty of food and allows fishing activities at times of critical need of fish. There is clear link between Indigenous knowledge and modern scientific fisheries practices. Also the methods used must safeguard the sustainability of fisheries and the general biodiversity. This shall ensure sustainable community livelihoods. Sustained production of fish stocks should give local people greater opportunities to generate incomes hence reducing levels of poverty in the Victoria Basin. The incorporation of these into fisheries work can lead to more informed, equitable and effective policy and management practices. This study provides recommendations from this and other studies.
Investigation of chemical kinetics of pyrite ore roasting for production of sulphuric acid
(2019) Hiji, Morris
The large-scale production of mine wastes and their secure disposal has been a problem of global importance. In this work, the mine waste from Merelani, crude overburden pyrite ore was converted into a value added chemical, sulphuric acid. XRF, XRD, AAS and modified ASTM D-2492 tests were used to investigate the mineral and chemical composition of the ore. It was revealed that the ore comprised about 60% w/w of mineral pyrite (FeS2). The evaluation of XRD pattern shows that the pyrite is of good quality according to the International Centre for Diffraction Data (ICDD). The elucidation of chemical kinetics of roasting of the ore to form a key precursor in the production of sulphuric acid, sulphur dioxide, revealed pseudo first order kinetic with respect to solid reactant in gas-solid system and optimum roasting temperature of 750° C. The activation energy (Ea) value of 15 kJ/mol was deduced from Arrhenius equation suggesting that the roasting reaction was controlled by diffusion of oxygen through the ash layer to the reacting surface. The main gaseous product of roasting crude pyrite ore was then converted into sulphuric acid, which apart from providing proper mitigation to the environment, but also serves as a social˗economic income to local people. The grade of sulphuric acid obtained was 40% w/w which is sufficient for battery acid use. The techno-economic evaluation of a small-scale plant of converting crude pyrite into sulphuric acid was done with the aid of SuperPro Designer simulator. The plant involves five major sections namely: size reduction, pyrite roasting, gas cleaning, formation of NO gas, formation of NO2 gas and acid chamber. Both the capital investment and operating cost vii were estimated by standard engineering cost estimation methods in evaluating chemical process economic viability. The economic indicators showed that the project is feasible with estimated value of NPV (3,503,000 USD), IRR 18.05% and PBP of about 3 years. Sensitivity analysis results were comparable with theory where the unit production cost decrease; the NPV and IRR increase with increasing plant production scale of maximum limit of 1.4.
Modelling dynamics of fusarium wilt of cashew plants with control strategies in the south-eastern region of Tanzania
(The University of Dodoma, 2023) Chilinga, Fatu M
This research aims to study the Fusarium wilt disease and its effects on crop production in Tanzania, particularly on cashew plants in the south-eastern region. The study proposes four mathematical models to analyse the different aspects of the disease and its impact on crop production. The first model describes the dynamics of the disease in a natural environment, taking into account the interactions between infected and susceptible plants. The second model addresses the impact of decomposed disease-induced dead plants on disease transmission. The third model investigates the effect of increasing farming awareness on the disease's dynamics and transmission. The fourth model examines the optimal control measures that can be implemented to control the spread of the disease and minimise its impact on crop production. The global and local stability was analysed using the Lyapunov function technique and the Routh-Hurwitz stability criterion. The sensitivity analysis was performed using the normalised forward sensitivity index and the Partial Rank Correlation Coefficient (PRCC) method. The optimal control problem was solved using Pontryagin's Maximum Principle. The study showed a very high disease transmission rate between infected and susceptible plants. The decomposed disease-induced dead plants also played a significant role in transmitting the disease by increasing the fungus saturation in the soil. However, increasing farming awareness of the disease tended to lower the disease transmission rate. The optimal control analysis revealed that using a combination of fungicides and advertisement was the most effective way to minimise the infection and the cost of implementing control strategies for farmers.
Statistical models and quality indicators for evaluation of clinical care among pediatric patients living with HIV/AIDS in Dar es salaam, Tanzania
(The University of Dodoma, 2021) Ismail, Abbas
Pediatric HIV patients are not randomly distributed and health services are not randomly allocated, and available methods for measuring Tanzania’s health care have not adequately addressed methodological strength of the indicators on providing valid estimates. This study intended to identify statistical methods and quality indicators for pediatric health care evaluation in Tanzania. The quality indicators were computed using proportions. The cut off values of the quality indicators in classifying levels of HIV pediatric health services were obtained. Inferential analysis was involved in obtaining quality indicators with clinical relevance and to achieve, different forms of survival analysis and Generalized Estimating Equations were fitted. After identifying quality indicators with clinical significance, ranking of health facilities based on risk adjusted models was also done. The indicators ‘eligart’ and ‘eligcotrm’ have shown clinical relevance on performance measures of facilities. Independence and exchangeable count generalized estimating equations, and frailty models for mortality rates were preferred methods in evaluating clinical relevance of the process quality indicators. The study concluded that process indicators of providing early ART initiation and provision of cotrimoxazole prophylaxis were important functions in monitoring and evaluation of facility performance. Hierarchical models for facility clustered level data can be used for performance assessment. Further studies should define more indicators and evaluate whether or not the inclusion of more detailed patient and facility health characteristics in adjusted models significantly alter quality reporting system.

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