Recently Defended Phd Thesis

Name of Candidate: Gideon Oluyinka LAYADE
Name of Supervisor: Dr J. A. Adegoke
Title: NEW QUANTITATIVE INTERPRETATION OF IRON-ORE DEPTH-TO-BASEMENT VARIATION IN AIRBORNE AND GROUND MAGNETIC SURVEYS AT GBEDE AND AJASE, OGBOMOSO, SOUTHWEST NIGERIA
Year: 2015
Abstract:The Depth-to-Basement (DB) of magnetic minerals is important in decision making for further economic investment. This is often obtained from airborne magnetic survey due to challenges associated with ground survey such as topography, seasons, time taken and cost of survey. Airborne DB are always of higher order of magnitude than those obtained from ground magnetic data leading to misrepresentation of in-situ DB. This study was designed to develop a new technique of interpretation which corrects the DB variation obtained from aeromagnetic and ground survey data.

Data on the aeromagnetic sheet 222 of Ogbomoso covering a total area of 3025 km2 were acquired from Nigeria Geological Survey Agency while proton precession magnetometer was used to measure Total Magnetic Intensity (TMI) for Gbede (10500 m2) and Ajase (15300 m2) iron-ore deposits. A new quantitative method tagged Data-Coordinate Interpolation Technique (DCIT) was developed by matching the secondary and primary data. Aeromagnetic map was contoured and digitised at ratio 10:1 airborne to ground spacing while data interpolation was carried out on the aeromagnetic map using appropriate software. The extracted data were re-contoured and gridded to produce a set of interpolated aeromagnetic DCIT data. The reliability of the technique was checked by using three methods of interpretation, Peter’s Half Slope Method (PHSM), Analytic Signal Method (ASM) and Euler Deconvolution Method (EDM) respectively. Data were analysed using descriptive statistics.

The ground, airborne, DCIT data average magnetic DB at Gbede using PHSM, ASM, EDM were 5.34±1.50 m, 587.44±125.30 m, 6.16±2.09 m; 5.66±1.75 m, 433.01±120.80 m, 5.79±2.07 m; and 5.74±0.88 m, 931.86±250.67 m, 5.95±1.59 m, respectively. Also at Ajase, DB for ground, airborne, DCIT data were 5.79±1.81 m, 718.10±208.23 m, 6.47±2.28 m; 5.53±1.90 m, 577.05±187.30 m, 5.55±2.90 m; and 8.75±1.47 m, 929.46±235.45 m, 7.88±1.52 m, respectively. Furthermore, the average DB for all the methods at Gbede with respect to ground, airborne, DCIT data were 5.58±1.38 m, 650.77±165.62 m, 5.97±1.92 m, respectively. Also at Ajase, average DB for ground, airborne, DCIT data by all the methods were 6.69±1.73 m, 741.54±210.33 m, 6.63±2.23 m, respectively. The results of the three methods when DCIT was adopted indicate minimal variation and they were of the same order of magnitude compared to raw airborne.

The newly developed Data-Coordinate Interpolation Technique was able to correct the variation which normally exists between the ground and airborne data. It is recommended to ensure accuracy, minimise time spent on the field and cost.

Keywords: Magnetic data, Iron-ore, deposit, Depth-to-basement variation, Total Magnetic Intensity


Name of Candidate: Raphael Oluwole AKANDE
Name of Supervisor: Dr E. O. Oyewande
Title: DEVELOPMENT OF A GENERAL POTENTIAL FOR THE
MOLECULAR DYNAMICS OF ION-SPUTTERED SURFACES
Year: 2015
Abstract: Erosion of surface atoms of solid materials by ion bombardment (surface-sputtering) causes nano-ripples and quantum dots to self-organise on the surfaces. The self-organisation was shown, in some sputtering experiments, to be influenced by unexpected contaminants from vacuum walls. Existing inter-atomic-interaction potentials of Molecular Dynamics (MD) simulations for studying this are unsuitable because they assume two-particle collisions at a time instead of many-particle collisions at a time (Wider-area Perturbations, WP). This study was designed to develop a suitable potential that incorporates WP of the MD.

Stochastic interactions were assumed in the wider-area perturbations and modelled as a Lorenz chaotic system. This was initially used to study how the chaotic surface bombardments and sputtering events perturbed the material's MD. But it was unsuccessful because of its inadequacy in the parametrisation of contaminants and re-bombardments of previously sputtered surface atoms. Thereafter, a new parameter, the Photon Absorption Potential Coefficient (PAPC), was developed to accommodate the diverse possible atomic compositions of materials, and to generalise the new potential for the changes in interactions that would arise from different material-ion/contaminant combinations. Calculations of the PAPC were performed for some sample materials which included Au, Fe, CSiGeW, CSiGeWTi, CSiGeWTiO, SrNdCuO, and LiFeAs. Consequently, a general potential was developed to account for the possibility of wider-area perturbations due to contaminants. Numerical calculations of the developed potential were also performed on the sample materials above. Dynamics of Au and Fe were studied with O bombardments/contamination (oxygenated environments), and those of CSiGe were studied with W, Ti, and O. Finally, calculations were performed on the sample materials with the more common existing potentials.

The Lorenz results showed Gaussian spreads with concentric patterns, which were inadequate to model the perturbations. The developed PAPC is given byA_c=1/Z [tanh^(-1)⁡〖(Z^- )+tanh^(-1)⁡(Z^+ ) 〗 ], where z is the atomic number,Z^-=(Z_v^-)/|Z-Z_v^- | ,Z^+=(Z_v^+)/|Z-Z_v^+ | ,z_v^- andz_v^+ are the number of electrons after ionization for gain and loss, respectively. The developed general potential is given byV=γ["exp" (1/πσ)-κμ/γ^2 ]Γ(ζ) where γ,σ,κ, μ, ζ, Γ are the energy of the incoming ion, the distance covered by a conical projection of the ion, incidence spot occupation density, ZA_c, sputtering activation constant for approaching ion, and activation function respectively. Graphs of the minima of V versus the number of added ions (contaminants) gave measures of changes in the MD (phase-shift). It was found that the phase-shift of Au stabilised for just five atoms of oxygen while that of Fe did not, when interacting in separate oxygenated environments. A different phase shift was recorded for CSiGe which reflected the usage of different contaminants, under subsequent bombardments with W, Ti and O, in transformations to CSiGeW, CSiGeWTi, and CSiGeWTiO. These results and those for the sampled superconducting materials, such as SrNdCuO and LiFeAs, showed a sensitivity of the general potential, and insensitivity of the existing potentials, to the type and environment (internal) of the atoms of these materials.

The developed general potential that incorporated the wider-area perturbations of the dynamics of ion-sputtered surfaces is suitable for describing their molecular dynamics.

Keywords: Interaction potential, Surface sputtering, Particle interaction, Molecular dynamics.

Name of Candidate: Emmanuel OyeyemiOYEKUNLE
Name of Supervisors: Dr Rachel I. Obed; DrBidemi I. Akinlade
Title: OPTIMISATION OF PROTECTION IN THE TREATMENT OF
CERVICAL CANCER PATIENTS USING COBALT-60 HIGH DOSE RATE BRACHYTHERAPY AT UNIVERSITY COLLEGE HOSPITAL, IBADAN
Year: 2015
Abstract: High-Dose-Rate brachytherapy (HDR-BT) is an advanced radiotherapy technique crucial to cervical cancer treatment worldwide. This technique, pioneered in Nigeria by University College Hospital (UCH), Ibadan, delivers high radiation dose for tumour treatment but can also subject the surrounding Organs-At-Risk (OAR) to excessive radiation. Without Quality Assurance (QA) of HDR-BT, the cervical tumour may be under-treated and late complications may also arise in OAR, specifically bladder and rectum. This study was therefore designed to undertake QA in HDR-BT through assessment of equipment, treatment plans (TPs) and doses to OAR with a view to achieving optimal protection in the treatment.

The Air-Kerma-Strength (AKS) of Cobalt-60 used in HDR-BT at UCH was measured with ionization chamber and compared with that obtained from Iridium-192 at Charlotte Maxeke Hospital (CMH), South Africa. Ethical approval was obtained for this study. At UCH, 311 patients given prescribed doses (Pd) of 15 – 21 Gy in three sessions with tandem-ring (185 patients) with no Rectal-Retractor) and vaginal-cylinder applicators (126 patients) between July 2008 and August 2013 were considered for total time index (TTI) evaluation. Non-availability of RTR made it difficult to maximize rectum positional-distance from high radiation region. A fixed tandem-ring ratio 1:1 was used to generate TPs in patients treated with tandem-ring applicators. The parameters Total Reference Air Kerma (TRAK), TTI, Treatment Time (TT), Isodose Volume (IV) and Dose to bladder (Db), Dose to rectum (Dr) and dose to a reference point (DB) were calculated using standard treatment planning software. Dwell Times (DTs) of 185 TPs were modified using variable tandem-ring ratios and the same parameters re-evaluated. The International Commission on Radiological Units and Measurements recommended maximum of 90% (bladder) and 75% (rectum) of Pd as dose limits. Positional-coordinates of OAR to achieve lower limits were deduced on HDR-BT radiographs to optimise protection using the existing 1:1. Doses to OAR in 65 patients using tandem-ring applicators with RTR were also assessed at CMH for standardisation. Absorbed-doses at both hospitals were converted to equivalent-doses (EQD2) for comparison. Data were analysed using descriptive statistics and student’s t-test.

Measured AKS of Cobalt-60 and Iridium-192 increased from manufacturers’ values by (< recommended 3%) respectively. TTI decreased (0.434 – 0.199 Gy m2 s/h Gy) with tandem-lengths in tandem-ring applicators, but increased (0.245-0.373 Gy m2 s/h Gy) with cylinder-diameters in cylinder-applicators. The means of parameters deviated by and for respectively with DTs modification. Lower mean values are an indication of optimisation. The positional-coordinates (x,y,z) ranged from 0.00 – 2.16 cm, 1.03 – 4.59 cm and 0.28 – 4.31 cm to achieve ≤ 80 % of Pd to the bladder, its. Also, rectal positional-coordinates (x,y,z)were within 0.00 – 0.00 cm, 0.20 – 4.20 cm and 0.00 – 4.44 cm for ≤ 65% Dr. The EQD2bladder ranged from while EQD2rectum ranged from at UCH and CMH respectively.
Measured Cobalt-60 Air-Kerma-Strength is acceptable for high-dose-rate brachytherapy but treatment plans using variable tandem-ring ratios is preferable. Organ-At-Risk (bladder) doses are comparable at the two study locations but higher equivalent-doses for rectum at UCH is attributed to lack of rectal-retractor.
Keywords: High-dose-rate brachytherapy, Cervical Cancer, Optimization of Protection, Organs-At-Risk  
Name of Candidate: Rufus AKINNUBI
Name of Supervisor: DrMojisola O. ADENIYI
Title: MODELLING DIURNAL PATTERN OF TURBULENT HEAT FLUXES FROM ROUTINE METEOROLOGICAL DATA USING LOWWIND SPEED EXCESS RESISTANCE PARAMETERIN SOUTHWESTERN NIGERIA
Year: 2015

Abstract: Turbulent sensible heat 〖(Q〗_H)and latent heat 〖(Q〗_E) fluxes areusuallymodelledusing the Aerodynamic Resistance Approach (ARA)in the Global Climate Models (GCMs). TheQ_HandQ_Earecrucial inmonitoring global energy budget for climate variability and climate change predictions. However, the windspeed-dependentexcess resistance (〖κB〗^(-1)) needed inARA to parameterise Q_H and Q_Ehas only been formulated for high wind speed condition, it is yet to be formulatedforthe humid tropical region where low wind speed is prevalent.Therefore, this study wasdesigned to derive and evaluate the performance of a more appropriate 〖κB〗^(-1)in ARA formodellingdiurnal pattern of QH and QE inlow wind speed condition.

The〖κB〗^(-1)was derived fromkRe^n-ln⁡(z/z_0m ) based on combined algorithms ofBrutsaertand Monin-Obukhov Similarity theory. Surface roughness length〖(z〗_0m), Stanton number (k) and exponent (n) of the Reynolds number (Re) were determined using Cartesian analysesand field data.Hourly data from 2004 to 2010 were collected for air, surface and soil temperature〖(T〗_a,〖T_s and T〗_soil), global radiation〖(Q〗_L), wind speed (u),Q_Hand Q_Efrom the Nigerian Micrometeorological Experimental sites at Ile-Ife,Ibadan andsix other southwesternstations through the Nigeria Meteorological Agency,Oshodi.TheQ_HandQ_E were computed using ARA givenas(ρC_p (T_s-T_a ))/(r_a+ 〖κB〗^(-1) ) and (ρc_p (e_s-e_a ))/(γ(r_a+〖κB〗^(-1)))respectively, where ρC_p,r_a,γ, e_s and e_a are volumetric heat capacity, aerodynamic resistance, psychometric constant, saturated vapour pressure for soil and saturated vapour pressure for air respectively. Values ofQ_Hand Q_Ewere simulated usingderived〖κB〗^(-1 )andother eight standard GCMs〖κB〗^(-1)schemes. These werecompared with the field valuesfor validationusing coefficient of determination〖(R〗^2), Mean Bias Error (MBE) and Root Mean Square Error (RMSE) statistics.

The valuesof z0mand k were 0.0260± 0.0013 m and 6.66 ± 0.01 respectively. The n-value was 0.0200± 0.0005,with a corresponding Re value of 39.93 ± 4.34.The derived〖κB〗^(-1)was6.66〖Re〗^0.02-5.47, with a corresponding value of 2.20 ± 0.33, while the values for existing〖κB〗^(-1) schemes ranged from 6.60 ± 1.34 to 14.41 ± 3.34 respectively. TheR^2,MBE and RMSE for Q_Hwere 0.89 ± 0.04, 6.32 ± 1.38 Wm-2 and 13.31 ± 1.23 Wm-2; while forQ_E were 0.80 ± 0.08, 8.03 ± 4.29 Wm-2 and 16.64 ± 7.87 Wm-2 respectively using derived〖κB〗^(-1). TheR^2, MBE and RMSEfor Q_Hwere 0.20- 0.48; 17.11-54.11 Wm-2 and 25.51- 60.34 Wm-2, while forQ_E were 0.20 - 0.58; 24.11- 48.11 Wm-2 and 35.11- 60.71 Wm-2 respectively for existing GCMs. The derived〖κB〗^(-1)gave significant correlations, while standard GCMs〖κB〗^(-1) gave insignificant correlationsat 0.05 level. More reliable results were obtained using derived〖κB〗^(-1).

The incorporation of excess resistance factorimproved the performance of the aerodynamic resistance approach in southwestern Nigeria. The derivedexcess resistance factoris therefore recommended for regional modelswithin humidtropics.

Keywords:Sensible heat flux, Latent heat flux, Reynolds number, Low wind speed.

Name of Candidate: Samson OlatubosunAISIDA
Supervisor: Dr E. O. Oyewande
Title: MOVE-BIASED MONTE CARLO SIMULATION METHOD FOR PROTEIN NATIVE STRUCTURE PREDICTION
Year: 2016
Abstract: Proteins are linear polymers of Amino Acid (AA) sequences, execute (function) genetic code inscribed in DNA of organisms, and have functionality that depends on their Native Structure (NS). Experimental methods for protein NS determination are complicated, expensive and time-consuming. Consequently, Computational Methods (CM), including Monte Carlo (MC), aim to ameliorate these challenges. However, the CM still suffers from complexity and inconsistency in NS Prediction (NSP). This study was designed to develop a modified MC method tagged Move-Biased MC (MBMC) method that simplifies the complexity of existing MC and makes it consistent for NSP.

Protein was described as coarse-grained structure and folding as Self-Avoiding Walks (SAW) on square lattices. Relative Probability Parameters (RPP) was introduced to determine natural probabilities of protein conformations from SAW and to simulate the desired sequence length from their (RPP) optimal combination. Thereafter, a graphical algorithm was developed to group the SAW steps into hydrophobic and polar AA units according to the Hydrophobic-Polar (HP) model. The MBMC method was developed as a coupling of diagonal-pull move bias (MB) on the lowest energy SAW conformation. The materials for testing the MBMC method included eight Bench-Mark Sequences (BMS) from the protein databank such as SI-1, SI-2, SI-3, SI-4, SI-5, SI-6, SI-7, and SI-8 with sequence lengths 20, 24, 25, 36, 48, 60, 64, and 85 amino acids, respectively. The lowest energy (consistency in prediction of NS), computation time, and algorithmic steps of the MBMC method was compared with some existing methods [such as Conventional MC (CMC), Genetic Algorithm (GA), Evolutionary MC (EMC), Ant Colony Optimization (ACO), Hybrid Elastic Net Algorithm (ENA)]. Data were analysed using inferential statistics.

The optimal combination of the RPP for the MBMC algorithmwere 0.71, 0.02, 0.25 and 0.02 for up, down, leftand right orientations, respectively.The HP model was used to compute the energy of the NS obtained from the MBMC method as -9, -9, -8, -14, -23, -35, -42, and -52, for the BMS respectively. In contrast, for GA energies reported were -9, -9, -8, -12, -22, -34, -37, and no record for eighth BMS; for ACO they were -9, -9, -8, -14, -23, -34, -32, -53; for EMC (and ENA) they were -9, -9, -8, -14, -23, -35 (-36), -39, -52 (no record); for CMC they were -9, -9, -7, -12, -20, -33, -35, and no record for the eighth BMS. Also, MBMC method consistently predicted the NS of the BMS in 8.90, 8.51, 8.37, 9.14, 9.45, 9.24, 9.46, 9.52, and 12.85 seconds, respectively. In contrast, the GA computation times were only reported for the first four BMS as 5.60, 6.00, 3.66, 54.60 seconds; and the EMC times (first seven) as 9314, 6929, 7202, 12447, 165791, 74613, 203729, 504809 seconds. Moreover, MBMC has fewer algorithmic steps and simpler simulation procedure than CMC, GA, EMC and ENA methods.
The developed Move-Biased Monte Carlo method has simpler algorithmic steps than the existing Monte Carlo methods and consistently predicts the native structure of proteins faster than existing algorithms.
Keywords: Protein folding, Coarse-grained model, Hydrophobic-Polar lattice model, Monte
Carlo simulation, Protein native structure.

Name of Candidate: Jacob Dele AYANDA
Name of Supervisor: Dr O. I. Popoola
Title:
Year: 2016
Abstract: 
Name of Candidate: Taofik Titus OGUNSEYE
Name of Supervisors: Dr O.I. Popoola; Dr O. E. Awe
Title: COMPUTATION OF THERMODYNAMIC PROPERTIES OF EARTH'S INTERIOR USING SELECTED MODELS
Year: 2016
Abstract:Adequate understanding of the earth’s interior requires determination of the Thermodynamic Properties (TP) of constituent minerals at very high temperatures and pressures. Earth models especially the common Parametric Earth Model Database (PEMD) have been used for TP determination but these methods are only suitable for the Lower mantle (Lm). Hence, it is necessary to develop a composite model that is suitable for other regions in the earth’s interior together with the Lm. This study was aimed at using Selected Earth Models (SEMs) for determining TP of the Lm and other regions in the earth’s interior.

The Transition zone (Tz), Lm, Outer core (Oc) and Inner core (Ic) regions in the earth’s interior were selected for the study. The SEMs comprised Preliminary Reference Earth Model (PREM), Anderson Temperature Distribution Model (ATDM), the mean sound velocity model ( ), P wave model ( ), S wave model ( ) and Isothermal Pressure model ( ). Bulk moduli ( ), P and S-waves velocities , density ( ), pressure ( ) were obtained from PREM while temperatures ( ) were obtained from ATDM to formulate a model. The TP: Gruneisen parameter (Gp), Thermal Pressure Gradient (TPG), Debye temperature (Dt) and Coefficient of Thermal Expansion (CTE) were determined from , ; , , ; and , , , respectively using: , , and ; where is the mean atomic mass. The TP obtained by SEMs for Lm were compared with existing values from PEMD. The data obtained were analysed using Student t-test at .

The Dt and Gp from SEMs for Tz, Lm, Oc and Ic regions ranged from 711.9to 897.7 K and 0.95 to 2.85; 986.6to 1309.0 K and 0.41 to 3.30 ; 1144.0to 1573.3 Kand 1.48to 1.64; 229.2 to 245.8 K and 1.70to 2.66,respectively. The TPG and CTE from SEMs for Tz, Lm, Oc and Ic ranged from 3.85 to 27.2 × 10-3 GPaK-1 and 1.55to 14.6 × 10-5 K-1 ; 5.019to 5.648 × 10-3 GPaK-1and 8.22 to 21.6 × 10-6 K-1 ; 1.78to 3.54 × 10-3 GPaK-1 and 3.05 to 3.29 × 10-5 K-1 ; 1.00 to 1.55 × 10-2 GPaK-1 and 7.43 to 12.6 × 10-6 K-1 respectively. The Dt, Gp, TPG and CTE from PEMD for Lm ranged from 1032 to 1303 K, 0.98 to 1.30, 5.001 to 5.565 × 10-3 GPaK-1and 7.77 to 19.12 × 10-6 K-1, respectively. The t- test results of Dt, Gp, TPG and CTE for Lm from SEMs compared to PEMD were significant with the probability values: 0.00, 0.02, 0.00 and 0.00 respectively.
The new model developed was suitable for determining the thermodynamic properties of the Lower mantle and other regions in the earth’s interior. The developed model is recommended for future research work in Mineral Physics.

Keywords:Preliminary Reference Earth Model, Earth interior, Debye temperature, Gruneisen parameter.

Name of Candidate: Jimoh Christopher OLOWOOKERE
Name of Supervisor: DrN. N. Jibiri
Title: RADIATIONDOSE AUDIT OF COMMON X-RAY DIAGNOSTIC PROCEDURES OF PATIENTS AND IMPLICATIONS FOR CANCER INCIDENCE IN SOUTHWESTERN NIGERIA
Year: 2016
Abstract:One of the objectives of x-ray examination is high quality images; however administered radiation doses may be harmful to patients’ health. Data on radiation dose to patients are scarce, and thus hinders the determination of local and national reference dose levels specific to a country owing to the differences in patient anatomy and radiological practice among nationals of different countries. This study was therefore, designed to determine the patient doses, local reference dose levels and estimate cancer risk based on administered dose at selected radiodiagnosticcentres in Southwestern Nigeria.

Twelve radiodiagnosticcentres were purposely selected across Lagos (3); Ogun (2); Oyo (1); Osun (4) and Ekiti (2) for this study. Exposure parameters including: peak voltage; tube load (mAs); focus-to-skin distance were obtained from x-ray machines during radiographic procedures. Quality control (QC) tests were performed using standard calibration method. Anthropometric data from 689 consented subjects were obtained for chest (353) Postero-Anterior (PA) and Antero-Posterior (AP) for abdomen (20), pelvis (35), skull (56), lumbar spine (87), thigh (12), leg (46), knee (17) and hand (63) examinations. Measurement of Entrance Surface Dose (ESD) was carried out with thermoluminescent dosimeters and converted to Dose-Area Product (DAP). Organ Dose (OD) and Effective Dose (ED) were determined using appropriate software. Organ doses were used to estimate the expected number of cancer incidences resulting from the examinations. Preliminary Local Reference Dose Levels (PLRDLs) were determined, and Patient Parametric-Exposure Estimation (PPEE) models which served as guides in the choice of appropriate exposure parameters for dose optimisation were developed. Data were analysed using descriptive statistics and compared with National Radiological Protection Board levels.

The QC results showed that 66.7% of the x-ray machines fall within the internationally acceptable tolerance limit of ±5.0% of exposure parameters reproducibility.The ESD (mGy) for chest PA, abdomen AP, pelvis AP, lumbar spine AP, skull AP, leg AP, knee AP, hand AP and thigh AP were 2.32±0.19,11.72±2.62,4.05±0.54,4.74±0.72,7.07±0.67,1.27±0.19,1.59±0.34,1.33±0.19,0.50±0.05; and the DAP (Gy cm2) were 3.06±0.30,17.16±4.96,3.28±0.47,2.72±0.44,4.53±0.05,1.14±0.15,1.53±0.23,0.92±0.13,0.18±0.02 for chest PA, abdomen AP, pelvis AP, lumbar AP, skull AP, leg AP, knee AP, hand AP and hand AP projections respectively. The ED ranged from0.08-2.56 mSv. The ranges of cancer incidences expected per annum for patients undergoing chest PA examinations for different organs were: lung (227-452), breast (28-207), easophagus (8-26), stomach (28-78) and liver (14-95). The proposed PLRDLs for ESD (mGy) and the corresponding DAP (Gy cm2) were2.95(3.14), 22.31(28.59), 6.63(4.77), 5.87(3.20), 9.04(5.06), 1.51(2.04), 2.78(2.09), 2.39(1.44), 0.69(0.25) chest PA, abdomen, pelvis, lumbar spine, skull, leg, knee, hand and thigh (AP projections) respectively. The determined PLRDLs were higher than the National Radiological Protection Board reference levels by factors ranging from 1.70-19.70 and 2.20-31.40 for ESD and DAP, respectively. The developed models for estimating patient thickness(〖 t〗_e) from eight (W) were:t_(e,male,chest)=0.15W+12.14 (R^2=0.91)andt_(e,female,chest)=0.17W+11.79 (R^2=0.90) for standard male and female adults respectively.

Patients undergoing selected diagnostic x-ray procedures in Southwestern Nigeria received high doses and have increased risk of cancer. The established local reference levels could help in dose optimisation for radiological practices in Southwestern Nigeria.
Keywords: X-ray examinations, Local reference dose levels, Dose optimisation, Cancer  
Name of Candidate: Kolawole Peter FASAE
Name of Supervisor: Dr N. N. Jibiri
Title: CONTRIBUTIONS OF NATURAL RADIONUCLIDES IN CHEMICAL FERTILIZERSTO FARM SOIL RADIOACTIVITY AND THE COMMITTED EFFECTIVE DOSES TO HUMAN
Year: 2016
Abstract: The use of chemical fertilizers to replenish depleted soil nutrients due to over cultivationand erosion is a common practice. Natural radionuclides in these fertilizers can cause some radiological adverse health effects to animal, through indirect ingestion of fertilizer, including consumption of plants grown with fertilizers. Information on the level of contribution of chemical fertilizers to farm soil radioactivity and radiological health effects in Nigeria are scanty. This study was designed to assess the contributions of chemical fertilizers to farm soil radioactivity and Committed Effective Doses (CEDs) to human.

Samples of commonly used Nitrogen-Phosphorus-Potassium (NPK:15-15-15) and Single Superphosphate (SSP) fertilizers were collected from retail markets in southern and northern Nigeria, respectively. Three partitions (0.55m2 each) of rain-fed experimental farm was filled with Virgin Soil (VS), which was collected from government reserved forest in Ekiti State. The fertilizers (NPK and SSP) were applied separately to VS with NPK (VSNPK) and VS with SSP (VSSSP) usingbroadcasting method at 1.0 kg/m2. The third partition served as the control (VSC). Seeds of Tomato (Solanum esculentum K. Karsten) and vegetable (Amaranthus hybridus Linnaeus) were sown on the partitions after one week of fertilizers application. The contributions of chemical fertilizers to farm soil radioactivity and their transfer factors to plants were investigated using standard method. The activity concentrations of natural radionuclides in the fertilizers, soil and plant samples were measured using Sodium Iodide doped with Thallium (NaI(Tl)) detector. The CEDs were determined using standard equation as contained in Radioactivity in Food and the Environment (RIFE) documents. Data were analysed using descriptive statistics and one way ANOVA at .
The Mean Activity Concentrations (MACs) of in NPK and SSP were 4754.0±192.0, 156.0±99.0 and 9.4±4.0 Bq/kg; 301.0±36.0, 696.0±113.0 and 14.7±2.7 Bq/kg, respectively. The MACs of in soil samples of the were 204.0±2.4, 43.0±2.3 and 7.0±1.7Bq/kg; 352.0±1.9, 62.0±1.7 and 8.0±1.9 Bq/kg;285.0±3.3, 66.0±2.0 and 10.0±1.4 Bq/kg, respectively. The MACs of the three radionuclides in tomato samples of the VSC, VSNPK and VSSSP were 64.0±1.4, 18.0±1.7 and 7.0±1.7 Bq/kg; 125.0±2.1, 33.0±2.0 and 8.0±1.9 Bq/kg;122.0±1.7, 51.0±1.4 and 10.0±1.4 Bq/kg,respectively. were 72.0±1.4, 22.0±1.7and 8.0±2.6 Bq/kg; 133.0±1.7, 45.0±1.9 and 10.0±1.9 Bq/kg; 142.0±2.3, 57.0±1.7 and 13.0±2.1 Bq/kg for respectively. Differences in MACs were significant in samples considered. Use of NPK and SSP contributed and respectively to the activity concentrations of in the VSNPK and VSSSP compared to the VSC farm soil. Radionuclide transfer factors in the VSC,VSNPK and VSSSPranged from 0.36-0.66, 0.35-0.56and 0.43-0.78, respectively. The CEDs due to consumption of tomatoes and vegetable of VSNPK and VSSSPwere 0.22 and 0.11 and respectively, which are lower than the recommended CED of by International Commission on Radiological Protection (ICRP). The NPK and SSP fertilizers in the VSNPK and VSSSP contributed 54.0 and 130.0 %, respectively to the CED (tomatoes), 37.0 and 73.0 %, respectively to CED (vegetables) when compared to plants in the VSC.
Chemical fertilizers contribute to farm soil radioactivity and the committed effective doses to human is elevated more by Single Superphosphate fertilizer.
Keywords: Radiological effect, Farm soil radioactivity, Radionuclide transfer factors,
Chemical fertilizer

Name of Candidate: ItuenBasseyOKON
Name of Supervisor: Dr Oyebola O. Popoola
Title: DEVELOPMENT OF A HOMONUCLEAR AND HETERONUCLEAR INTERACTION POTENTIAL FOR BOUND STATE SOLUTION OF SCHRÖDINGER AND KLEIN-GORDON EQUATIONS USING NIKIFOROV-UVAROV METHOD

Year: 2016
Abstract: Bound state solutions of Schrödinger (SE) and Klein-Gordon (KGE) equations are important in studying energies of diatomic molecules. The interaction between such molecules is described by a suitable potential. Existing potentials could either describe homonuclear or heteronuclear molecules but not both. This study was designed to develop a potential for obtaining exact energies for both homonuclear and heteronuclear diatomic molecules.

Different forms of potentials, starting with Yukawa and extended Hulthen which are typical intermediate and short range potentials, respectively were combined to obtain trial potentials. These potentials were substituted into SE and KGE equations, which were reduced to a generalised hyper-geometric Nikiforov-Uvarov equation (NUE). This has the form: Ψ^″ (s)+((τ ) ̃(S))/σ(S) Ψ^' (s)+((σ ) ̃(S))/(σ^2 (S) ) Ψ(s)=0using standard Greene and Aldrich approximation to the centrifugal term, where and are polynomials of at most degree two while is a polynomial of degree one. The equations were solved analytically to obtain the normalised wave function in terms of orthogonal normalised function (Jacobi polynomial). Fortran algorithms were implemented for the resulting energy functions to obtain the numerical bound state energies of the different diatomic molecules. In order to determine the suitability of the potential for homonuclear and heteronuclear interaction, the energies obtained were compared with existing numerical results for energies of homonuclear and heteronuclear diatomic molecules. The following molecules were considered due to availability of data: Hydrogen (H2), Lithium Hydride (LiH), Hydrogen Chloride (HCl) and Carbon (II) oxide (CO). Results were obtained for principal quantum number n≥0 and orbital quantum number ≥0 . The bound state spectral diagrams were also obtained by plotting the bound state energies against the quantum state for different values of orbital quantum number. Data was analysed using descriptive statistics.

The potential developed was V(r)=(-V_0 e^(-2αr))/((1-e^(-2αr)))-(Ae^(-αr))/r+B/r^2 +C, where A, B and C are molecular bond length (A^0), molecular constant(1⁄A^0 )and potential range (A^0) respectively,V_o (cm^(-1) )is the potential depth, ∝is the screening parameter and is the intermolecular distance (A^0). The results of the bound state energies for n=0,l=0 were -4.52, -2.45,-3.80 and -11.06 eV, for H2,LiH, HCl and CO, respectively. While the existing literature results were -4.48,-2.41, -4.42 and -11.08 eV, respectively. These results agreed with existing results up to ± 0.14. For the bound state energies for these molecules were: -1.42, -5.92, -0.82, and -10.06 eV, respectively. Other numerical results obtained for showed that the bound state energies of these molecules increased with increase in quantum number. The bound state energy spectral diagrams showedquantisationof energy levels of these molecules, which werein agreement with existing literature.

The potential was suitable for obtaining bound state energies for both homonuclear and heteronuclear diatomic molecules.

Keywords: Diatomic molecules, Quantum numbers, Energy quantisation, Wave functions, Orthogonal solutions

Name of Candidate:Ismail Oyeleke OLARINOYE
Name of Supervisor: Prof. F. O. Ogundare
Title: DEPOSITION OF STOICHIOMETRIC RF – SPUTTERED ALUMINA THIN FILMS AND EFFECTS OF NEUTRONS AND HELIUM ION ON THE OPTICAL ANDMICROSTRUCTURAL PROPERTIES OF THE FILMS
Year: 2017
Abstract: The efficiency of solar cells has been identified to significantly improve through the use of stoichiometric Alumina Thin Films (ATFs), possessing stable optical properties as anti-reflectance coatings and passivation surfaces. Determination of the optimal values of deposition parameters {Radio Frequency Power (RFP), Oxygen Flow Ratio (OFR) and Annealing Temperature (AT)} for stoichiometric ATF remains a challenge. In addition, ionizing radiation has been reported to affect the optical and structural properties of some thin film materials. Information on stability of optical properties of pure ATF when exposed to neutron and helium ion (He+) is scanty. This research is therefore designed to deposit stoichiometric alumina thin films and investigate the effect of neutron and He+ irradiations on the optical and microstructural properties of the films.

The ATFs (50 nm thick) were deposited on glass substrates by the reactive RF-sputtering method. Pure argon and oxygen were used as the sputtering and reactive gases, respectively in a vacuum chamber. Films with different oxygen to aluminium ratio were deposited by varying RFP (150–250 W) and OFR (11–23%) at an argon flow rate of 1.0 SCCM. The effect of RFP, OFR and AT on the composition, optical {Refractive Index (RI) and Extinction Coefficient (EC)}, electrical (sheet resistance), and microstructural (phase and surface structure) properties of the deposited and selectively annealed (at 473 K and 573 K for 7200 s) ATF were determined using standard methods. The stoichiometric alumina films obtained were divided into two groups (one irradiated with He+beam and the other with neutron beam) for doses ranging from 6.0 x 1012 to 4.0 x 1013particles/cm2. The effects of the radiations on the optical and microstructural properties of the films were investigated using UV-VIS-NIR spectroscopy, X-ray diffraction analysis and the atomic force microscopy. Data were analysed using descriptive statistics and regression method.
Stoichiometric films were obtained at OFR of 11.0%, RFP of 250 W and post deposition annealing at 573 K. The films were structurally amorphous with average sheet resistance of 272 MΩ-square irrespective of the values of deposition parameters. The RI (1.7) and EC (0.1) for stoichiometric films both decreased exponentially with increase in OFR and RFP. Conversely, both RI and EC increased with higher AT. The RI and EC increased with He+ and neutron irradiation but with unchanged structural phase. The root mean square roughness (R_q) of the films increased from 7.8 nm for deposited film to 20.3 nm and 53.6 nm at the highest neutron and He+ dose, respectively. The variation of R_q with radiation dose (x) was found to fit well to the equations:R_q=0.0076 x^0.252 〖(R〗^2=0.96) and〖 R〗_q=0.0033 x^0.270 〖(R〗^2=0.90) for films irradiated with He+ and neutrons, respectively.
Stoichiometric alumina thin film deposited successfully. Neutron and Helium ion irradiations altered the optical and structural properties of the films. Alumina thin film is not suitable for optical applications in ionising radiation environment.
Keywords: Aluminathin film, Film stoichiometry, Ion irradiation, Optical properties

Name of Candidate: OludotunOmoniyiFALUYI
Name of Supervisors: Dr J. A. Adegoke
Dr O. I. Popoola
Title: EXPERIMENTAL APPROACH TO THE DEVELOPMENT OF A
MODELFOR THE CONTROL OF SALTWATER INTRUSION IN COASTAL FRESHWATER AQUIFERS
Year: 2017
Abstract: Underground freshwater flows naturally into the sea due to hydraulic head difference. Excessive abstraction of freshwater at coastal regions may reverse the direction of flow of mass flux of dissolved salts (J) leading to Saltwater Intrusion (SI) contaminating freshwater in coastal aquifers. The existing SI models are insufficient because porosity (∅), hydraulic conductivity and attenuation coefficient (λ_x) of the medium are theoretically chosen. This study was designed to investigate SI using experimental approach to develop a model that incorporates empirical properties of medium to determine J and the best medium that controls SI.
Darcy’s and Fick’s laws were used to develop a model which gives J as a function of seepage velocity(v), volume flux(Vx) and effective diffusion coefficient(Do). In validating the model, an experiment was designed to determine J and λ_x in which river bed sand were washed, dried and sieved into five different grain sizes of samples A(least ∅),B,C,D and E(greatest ∅) using electric sieve with mesh ranged150-500μm. The Ø of each sample was determined using volumetric technique. Two vertical arms of calibrated cylinder glass with diameter1.2×〖10〗^(-2) m were joined with a similar glass cylinder in the horizontal position which housed the samples. Samples screened at both ends of length x were inserted into the glass with air completely eliminated using displacement method before commencement of flow experiment. The v,V_x and D_o were determined for five samples after which J was determined at interface and at other points in which the results served as a guide for choosing boundary values for simulation of J in the model. The λ_x^' s(λ_x=v⁄D_o ) were determined from the gradients of plots of natural logarithm of J against flow length x for simulation and experiment. The model was used to analyse groundwater flow systems under the condition of absolute miscibility. The average concentration of saltwater at interface was C(0,t)=C_o=1025kgm^(-3)and at end point C(∞,t)=0. The results were compared with WHO standard of dissolved salts. Data were analysed using descriptive statistics.
The developed model was J=vC_o exp⁡(-v⁄D_o )x. The Ø A,B,C,D and E were: 0.250±0.009,0.300±0.002,0.330±0.001,0.375±0.001 and 0.420±0.002,respectively. Similarly, v, Vx and Do were:
0.79×〖10〗^(-6),0.19×〖10〗^(-6),0.331×〖10〗^(-6);2.62×〖10〗^(-6),0.79×〖10〗^(-6),0.366×〖10〗^(-6);10.13×〖10〗^(-6),3.34×〖10〗^(-6),0.399×〖10〗^(-6);13.10×〖10〗^(-6),4.91×〖10〗^(-6),0.404×〖10〗^(-6) and 17.50×〖10〗^(-6) ms^(-1),7.35〖×10〗^(-6) ms^(-1),0.468×〖10〗^(-6) m^2 s^(-1) for A,B,C,D and E,respectively. The J at interface where intrusion starts were: 0.81×〖10〗^(-3),2.69×〖10〗^(-3),10.38×〖10〗^(-3),13.43×〖10〗^(-3) and 17.94×〖10〗^(-3) kgm^(-2) s^(-1) for A,B,C,D and E, respectively. The J for simulation and experiment at x=0.14m from interface were: 5.44×〖10〗^(-5) and 5.63×〖10〗^(-5);0.890×〖10〗^(-5) and 0.342×〖10〗^(-5);0.261×〖10〗^(-5) and 0.318×〖10〗^(-5);0.173×〖10〗^(-5) and 0.218×〖10〗^(-5);0.136×〖10〗^(-5) and 0.124×〖10〗^(-5) kgm^(-2) s^(-1)for all samples respectively. The concentrations of saltwater at x=0.14m for simulation and experiment were: 336.3 and 312.7;685.4 and 894.5;999.2 and 993.6; 1011.8 and 1008.4; 1017.3 and 1017.9kgm-3for A,B,C,DandE, respectively. The J obtained from the model and experiment were in agreement having root mean square error of 0.0003. The λxfor simulation and experiment were: -2.84 and -2.60; -789; and -14.72; -24.89 and -26.30; -31.09 and -29.43; -34.89 and -35.53m-1for A,B,C,D and E, respectively. Acceptable concentration of saltwater by WHO for human consumption is 500kgm-3 indicating that condition for concentration ≤500kgm^(-3) was achieved by parametric configuration of sample A with λ_x=2.60.
The developed model predicted that the medium with the finest grain size controlled saltwater intrusion effectively.
Keywords: Volume flux, Coastal aquifer, Hydraulic conductivity, Freshwater, Saltwater intrusion.

Name of Candidate: Godwin BabatundeEGBEYALE
Name of Supervisor: Dr J. A. Adegoke
Title: OPTIMISATION OF CATION EXCHANGE CAPACITY OF CLAY IN X-RAY SHIELDING
Year: 2017
Abstract: Kaolin, a Natural Clay (NC), is used as remediation of Heavy Metals (HM) contamination because of its Cation Exchange (CE) property. Disposal of such contaminated clay is a challenge when it exists in large quantity. However, the presence of HM in NC enhances its CE property and may make it a potential shield for x-ray. Although NC has been used as radioactive waste containment, the usage of HM contaminated NC as x-ray shield has not been reported. This study was designed to investigate the optimisation of HM contaminated NC as a shield for x-ray.

Clay samples were identified and collected from six locations including Lalupon Lead Battery Dump Site (LLBDS) where the soil was identified as sand-clay (30:70). The samples were air-dried, crushed, and sieved using standard mesh ≤2μm. Each sample, excluding LLBDS, was divided into two portions: A1 and A2. One gram each from A1 was digested using standard procedure to determine the initial concentrations of HM. Each A2 was divided into forty-five samples per location. Forty samples were mixed with nitrates of HM determined at 400, 800, 1600, 3200 and 6400 ppm. The remaining five samples were mixed in similar concentrations with dissolved Lead Oxide (PbO) to allow for CE and filtered. The A2 residues were analysed for CE using standard method while the filtrates were analysed for change in both HM concentration and CE. Slabs of different clay thicknesses: 1,2,3,...10cm were made from the residues and exposed to x-ray energies (40,60,80,100 and 120 keV). The linear attenuation coefficients (λ) were determined using I=I_o e^(-λx), where I and I_o are transmitted and incident intensity, respectively. Thermal Conductivity (TC) and Diffusivity (TD) were measured to determine the suitability of clay slab as x-ray shield in addition to λ. The results were compared with that of concrete slab as specified by IAEA standard. Data were analysed using descriptive statistic and t-test at α_0.05.

The initial and subsequent concentrations of Pb, Hg, Fe, Zn, Cd, Cr, Ni, and Cu ranged 1.4-5652.3; 0.1-5844.6; 1.0-4456.5; 4.1-5908.1; 0.1-5643.6; 2.7-5854.4; 1.4-6124.2 and 0.8-6034.3 ppm, respectively. The CE of the residues and filtrates ranged 10.2-15.2 and 4.2-8.4 meq/100g, respectively. Attenuation coefficients at various energies for LLBDS, clay with nitrate and clay with PbO were: 3.47±0.02,1.64±0.14 and 2.63±0.17 cm-1; 2.77±0.02,1.52±0.06 and
1.73±0.15cm-1;2.28±0.2, 1.15±0.08 and 1.38±0.08cm-1; 2.01±0.2,0.99±0.03 and
1.15±0.05cm-1;1.72±0.02, 0.80±0.08 and 1.02±0.07 cm-1 while concrete were:
0.51,0.44,0.41,0.39 and 0.33 cm-1, respectively. The TC of slabs with nitrate of HM and PbO ranged 0.12-0.38 and 0.11-0.20 Wm-1K-1 while their corresponding TD ranged 4.18-9.29 and 5.12-7.31 m2/s, respectively. The values of concrete were: 0.13Wm-1K-1 and 1.7 m2s-1. The LLBDS and clay with PbO have best attenuation at highest energy with thickness 7 and 9 cm, respectively. The t-test showed that LLBDS and clay mixed with PbO were more effective than concrete.
Optimised heavy metal natural clay was effective in the cation exchange capacity of clay in x-ray shielding.

Keywords: Contaminated clay adsorption, Cation exchange capacity, X-rays attenuation,
Thermal conductivity.

Name of Candidate: OlanrewajuAdewunmi MOKUOLU
Name of Supervisor: Dr E. O. Joshua
Title: ELECTRICAL RESISTIVITY BASED EMPIRICAL MODEL FOR PREDICTING CASSAVA PLANTS’ (Manihotutilissimapohl, TMS 98/0505) TUBER YIELD ON SANDY-LOAM SOIL
Year: 2017
Abstract:Soil Electrical Resistivity (SER) is influenced by Soil Water Content (SWC), Organic Matter (OM), Cation Exchange Capacity (CEC), sand, silt and clay contents which affect plants’ productivity. Soil sample collection and laboratory analysis which have been the traditional methods for estimating plants’ yield are time consuming and expensive. There is need for predictive models for cassava (a major staple food crop in developing world) yield. A yield predictive model based on SER would be a good replacement to the traditional methods. There is dearth of information on the use of SER in yield prediction. This study was therefore designed to develop an empirical model for predicting cassava tuber yield using SER.

The study was conducted on 50 m x 135 m field containing 125 rows at 1 m apart, with each row measuring 40 m in length. The experimental field was located within the farm settlement of Federal College of Education, Abeokuta. The SER was conducted at 13 different points along each traverse at 3 m apart for 42 traverses. Wenner array was used for measuring SER at: 0–0.3 m (SER30) and 0–0.9 m (SER90) soil depths. The SER was determined from current (I) injected into the soil, potential difference (ΔV) and electrical resistance (R) using: SER=2πa∆V/I. Cassava stems were then planted on the rows at 1 m x 1 m spacing. Yield parameters (number of tuber, NT, average tuber length, TL and tuber weight, TW) were measured after twelve months. Soil properties: SWC, OM, CEC, sand, silt and clay contents were determined from soil samples collected within the zone of major biological activity (0.3 m depth), using standard methods. The data were analysed using descriptive statistics, correlation, linear regression, curve estimation and t-test analyses at α_0.05.

The SER30 and SER90 values ranged from 143.1–3065.6 Ωm and 316.7–455766.7 Ωm, respectively. The NT, TL and TW ranged from 1.0–20.0, 0.1–0.9 m and 1.0–3.6 kg, respectively. The SWC, OM and CEC ranged from 7.3–21.4%, 0.7–5.0% and 5.3–10.0 Cmol/kg, respectively. Sand, silt and clay contents ranged from 70.8–83.2%, 8.3–22.0% and 6.4–13.2%, respectively, indicating sandy-loam soil. The SER90correlates insignificantly with soil properties (r = 0.1–0.3) and yield (r = 0.0). The SER30 correlates significantly with soil properties (r = 0.6–0.7) and TW (r = 0.8) but insignificantly with NT and TL (r = 0.1, 0.0). Lower SER30 areas exhibited higher contents of soil properties and gave better yield. Curve estimation analysis showed SER30 and TW was best fitted to Lorentz distribution (R2 = 0.9) function given by: T_W≡1.59 + (7.52×〖10〗^2 )[(6.73×〖10〗^2)/(4(〖SER〗_30-3.38×〖10〗^2 )^2- (6.73×〖10〗^2 )^2 )]. No significant difference was observed between the empirical model and the experimental data.

The soil electrical resistivity predicted cassava tuber weight. Lower resistivity zones produced higher yield than higher resistivity zones.

Keywords: Soil electrical resistivity, Wenner array, Yield predictive model, Cassava and Soil properties.