Theses
Permanent URI for this collectionhttps://repository.ui.edu.ng/handle/123456789/421
Browse
12 results
Search Results
Item SOME ASPECTS OF THE ATMOSPHERIC ELECTRIC CLIMATE AT IBADAN(1980-07) ADEWOLU, D. O.The diurnal variations of the atmospheric electric Parameters and meteorological Parameters for the harmattan season of November 1978 to March 1979 are presented. The percentage variations of temperature are mirror images of those of vapour pressure which show pronounced depressions around noon when the little available moisture in the air near the ground is distributed over greater and greater heights by convection. The diurnal patterns of dust concentration, measured for the first time in this locality, is single periodic with minimum between 0400 hrs and 0800 hrs L.T. and maximum around 20 hrs L.T. This pattern is closely related to that of windspeed, and is explained in terms of the copious amount of dust transported southwards from the Sahara desert. The diurnal curves of the electric elements. I, H and p show pronounced “austausch” depressions around noon and marked peaks at 08.00 hrs which are attributable to the sunrise effect. An average value of the total nuclei concentration during the Harmattan months is computed to be about 2.8x10(10) particles per m(3) for this Station. This value is based on the measurements of the polar conductivities made for the first time in Ibadan.Item Luminescence Sensitisation of Natural Quartz Using Pre-Exposure Dose and Thermal Activation Techniques(2014) Oniya, E. O.Luminescence sensitisation is an important stage in the application of quartz in pre-dose retrospective dosimetry and dating. The existing techniques for sensitisation in quartz are Pre-Exposure Dose (PED) and Thermal Activation (TA). Previous works were centred on combined actions of PED and TA with less attention given to the separate contributions of these techniques in pre-dose sensitisation of quartz. This work was undertaken to determine the separate contributions of PED and TA in sensitisations of 110oC Thermoluminescence (TL) peak and Room Temperature Linearly Modulated Optically Stimulated Luminescence (RT-LMOSL) of quartz. Two sets of quartz samples, one from Oro in Kwara State (S2) and the other from Ijero-Ekiti, Ekiti State (S4) with high sensitisation signals were used. Each of the two sets was divided into two parts; the first was unannealed while the second part was annealed, following standard procedures. Each of the unannealed and annealed samples was further divided into 38 aliquots required for the protocol. Fourteen aliquots each of unannealed and annealed samples were given PED and another set of 14 aliquots were without PED. The TL and RT-LMOSL measurements were carried out on each aliquot using an automated (model-TL/OSL–DA–15). Sensitisation reproducibility of repeated TL measurements on 10 different aliquots of each of the unannealed and annealed samples was quantified using Coefficient of Variation (CV). Data were analysed using descriptive statistics. reader TL/OSL RISØThe sensitisation signals of the aliquots of unannealed samples without PED was higher than that of the aliquots with PED by factor of 76.0 % and 79.0 % for TL and RT-LMOSL respectively for S2 while the corresponding factors obtained for S4 were 45.0 % for TL and 14.0 % for RT-LMOSL. In annealed samples, the sensitisation signal of the aliquots with PED was rather higher than that of the aliquots without PED, by factor of 224.0 % for TL and 201.0 % for RT-LMOSL for S2 and for S4, it was by factor of 245.0 % for TL and 217.0 % for RT-LMOSL. The sensitisations reproducibility of aliquots of unannealed samples were found to be poor with CV of 33.5 % for S2 and 52.0 % for S4. This improved significantly in the annealed samples to CV 6.3 % for S2 and 9.0 % for S4. Luminescence sensitisation by pre-exposure dose was dominant in annealed quartz samples. Therefore, only annealed quartz samples are recommended for pre-dose retrospective dosimetry and dating. The use of 110oC thermoluminescence peak signal in sensitisation corrections of unannealed quartz is not advisable.Item Radiation Dose Audit of Common X-Ray Diagnostic Procedures of Patients and Implications for Cancer Incidence in Southwestern Nigeria(2016) Olowookere, J. C.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 hinder 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 radiodiagnostic centres in Southwestern Nigeria. Twelve radiodiagnostic centres 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 ± 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 ± 0.05,1.15,1.53 ± 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 from. 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 PLDRLs for ESD (mGy) and the corresponding DAP (Gy cm2) were;2.95(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 PLDRLs 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 from weight () were: 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.Item Fabrication and Characterisation of Superstrate Copper Zinc Tin Sulphide (Cu2znsns4) Thin Films Solar Cells(2013) Olopade, M. A.Greenhouse gases emitted from burnt fossil fuels are major contributors to global warming which currently threatens existence of life. Hence, the global campaign for the replacement of fossil fuels with solar energy. The Cu2ZnSnS4 (CZTS) thin film has emerged as a promising material for photovoltaic absorption layer in the fabrication of solar cells. Various methods of deposition have been used to fabricate superstrate CZTS thin film solar cells. However, there is limited information on the use of sol-gel method which is known to perfectly control chemical composition for the fabrication of this type of solar cells. In this study, a superstrate structured CZTS thin film solar cell was fabricated using the sol-gel method and thereafter characterised. The possibility of using paper tape during the fabrication process instead of photomask which is not always readily available was also investigated. Superstrate structured CZTS thin film solar cells were fabricated using atmospheric pressure chemical vapour to deposit SnO2:F thin film (as window layer). Also, spin coating method was used to deposit CdS thin film (as buffer layer) from the sol-gel of cadmium acetate, 2-methoxy ethanol, thiourea and polyethylene glycol. Sol-gel sulphurising method was used to deposit Cu2ZnSnS4 thin film (as absorber layer) from CuCl2, ZnCl, SnCl2 and thiourea (as sulphur source). Layers of the film were masked using paper tape, optimised and characterised following standard procedures before being used in the fabrication of (SLG)/FTO (SnO2:F)/Ag/CdS/CZTS/Al solar cell. The deposited films were characterised using scanning electron microscope for surface morphology, Jandel universal four point probe for sheet resistance, MD-10 X-ray Diffractometer for crystallography and AvaSpec-2048 UV-VIS spectrophotometer for optical properties. The CZTS thin film solar cells of active area 2.25cm2 were examined for their efficiencies using the Newport solar simulator under irradiation of 100 mW/cm2. The mean of the efficiencies of CZTS solar cells from sol-gel method were compared with previous work on screen printing and doctor-blade methods. The SnO2:F thin film obtained had a transmittance of 80% in the UV-Visible region of the electromagnetic spectrum and a sheet resistance of 15 Ω/sq which is within acceptable values for a window layer. The calculated energy band gap of the CdS and CZTS films from the transmittance and reflectance data were 2.40 eV and 1.51 eV respectively. This value for CZTS is closest to near-optimal direct band gap value (1.50eV) when compared with those obtained via screen printing (1.40eV) and doctor blade (1.41eV) methods. The X-ray diffraction pattern of the CdS film exhibit hexagonal structure with (002) orientation while CZTS film had kesterite structure with (112) orientation. The absorption co-efficient of CZTS film in the visible region was 104 cm-1. The X-ray diffraction pattern showed sharp peaks whereas broadened peaks were observed in the X-ray diffraction pattern obtained via doctor blade method. The fabricated solar cells with buffer layer thicknesses of 40 nm and 60 nm had efficiencies of 0.28 0.01% and 0.13 0.01% respectively when compared with screen printing (0.53%) and doctor-blade (0.55%). Superstrate Cu2ZnSnS4 solar cells have been successfully fabricated using sol-gel spin coating method and paper tape in lieu of photomaskItem Determination of Activity Concentrations of Natural Radionuclides and Radiation Hazard Indices in the Sediments of Ogun River(2012) Okeyode, I. O.River sediments are known to contain natural radionuclides, the concentrations of which if beyond certain limits can cause adverse health effects. The sediments from Ogun river provide large quantities of sand for construction purposes in Nigeria. Despite this, data are scarce on the natural radionuclides: 40K, 226Ra and 232Th distribution in the river sediments. This work was aimed at determining the spatial distribution of these natural radionuclides and their concentrations in the sediments of Ogun river, and to evaluate the radiological implications on the population living in houses built with the river sediments. A total of 320 sediment samples were randomly collected along the course of the river; 60 in the upper region (Igboho to Idi- Ata; Oyo – Ogun axis), 90 in the middle region (Olopade to Mile 8 Oba; Ogun –Lagos axis) and 170 in the lower region (Abata to Apa Osa; Lagos axis). The number of samples collected in each region was determined by accessibility. The samples were air dried, pulverized and sieved using a 2 mm mesh size. Two hundred and fifty grams of the sieved samples were transferred into plastic containers of uniform sizes, sealed and left for 4 weeks to attain secular radioactive equilibrium. The activity concentrations of the natural radionuclides in the samples were determined using gamma-ray spectrometer comprising 76mm x 76mm NaI(Tl) detector coupled to a multichannel analyser. These concentrations together with standard equations were used to evaluate indoor effective dose rates, radium equivalent, external and internal hazard indices, representative gamma index and Excess Lifetime Cancer Risks (ELCR) and results were compared with available data from India, Egypt and Turkey. Data were analysed using descriptive statistics. The activity concentrations (in Bq/kg) of 40K, 226Ra and 232Th ranged from 371.0 (middle) – 608.0 (lower), 5.6 – 20.4 (middle) and 5.0 (lower) – 23.1 (middle) respectively. These were similar to data from other locations of the world. The upper region of the river indicated no location effect, in the middle and lower regions, significant location effects were observed and these were attributable to industrial activities. The mean annual indoor effective dose rates were 0.31 ± 0.02 mSv (upper), 0.30 ± 0.05 mSv (middle) and 0.33 ± 0.05 mSv (lower region). The radium equivalent activity for upper, middle and lower regions respectively, were 65.16 ± 4.14 Bq/kg, 64.10 ± 10.78 Bq/kg and 71.00 ± 11.78 Bq/kg, while external hazard indices were 0.18 ± 0.01, 0.17 ± 0.03 and 0.19 ± 0.03. Internal hazard indices were and , representative gamma indices were 0.52 0.03, 0.51 0.08 and 0.56 0.09, whereas ELCR values were ,and .,01.021.004.021.005.023.031001.0141.031002.0137.031003.014The radiological hazard indices evaluated for Ogun river sediments were less than acceptable limits and therefore posses no radiation risk on the populations living in the houses built with materials incorporating the river sediments.Item Effects of Co2 and Ch4 Emissions on Climate Variability in the Tropics(2012) Ogunsola, O. E.Climate variability is indicated as anomalies in weather parameters such as rainfall and temperature. These are being influenced by greenhouse gas emissions such as carbon dioxide (CO2) and methane (CH4), amongst others. This variability is usually studied using General Circulation Models (GCMs) and empirical models obtained from analyses of data at synoptic weather stations. The GCMs give different predictions from model to model due to parameterisations of microprocesses embedded in them. Likewise, empirical models are often applicable to locations of studies and most stations in the tropics are yet to be analysed. Hence, this work was aimed at analysing and modelling both CO2 and CH4 concentrations over the entire tropics with a view to understanding their contributions to climate variability. Daily concentration data of CO2 and CH4 from the 12 stations, with minimum of 10-year data, within latitude 30oN and 30oS were obtained from World Data Centre for Greenhouse Gases, Japan. These data, between January 1996 and December 2005, were analysed using standardized anomalies, moving average and autocorrelation methods. Box-Jenkins iterative method which combines both moving average and auto regression analyses, was employed for modelling the concentrations (i) of the gases as a function of time. The suitability of the developed model was determined by comparing the predicted and measured monthly concentrations of these gases for the period January 2006 to December 2008. The standard deviations (i) of the concentrations of these modelled gases were correlated with Roy Spencer‟s tropical temperature anomaly data to ascertain their warming effect.The standardized anomalies showed seasonal variations and smoothening of these data by moving average revealed monotonic increase with time. The autocorrelation function showed that CO2 can be predicted with higher accuracy than CH4. The developed model was of the form:121111120)120(tctba for CO2 and 222222120)120(tctba for CH4, where ai, bi, c i and t represent the intercept, linear term coefficient, quadratic term coefficient and predictedmonth respectively. The mean annual concentrations calculated using the model for CO2 and CH4 in the northern hemisphere stations ranged from 381.5±0.3 to 384.3±0.3 ppm and 1793.5±1.4 to 1832.9±1.7 ppb respectively, while the measured values ranged from 382.9±0.2 to 384.5±0.2 ppm and 1787.3±1.4 to 1823.3±1.0 ppb respectively.Similar agreement was obtained between calculated and measured values for southern hemisphere stations. The correlation coefficient between predicted and measured concentrations of CO2 and CH4 for year 2006 to 2008 was 0.99 and 0.96 respectively. The i for CO2 and CH4 concentrations in northern hemisphere ranged from 0.3 to 0.9 and 0.5 to 3.3 respectively, while those in southern hemisphere ranged from 0.4 to 0.7 and 0.2 to 4.2 respectively. The i increased with climatic warming and had highest value for 1998, the warmest among the years considered. Concentrations of both CO2 and CH4 increased monotonically with time. The developed model predicted CO2 and CH4 concentrations adequately in the tropics and could also be used to predict their future concentrations and climate warming effectively.Item Radioactivity in Farm Soils and Food Crops Grown in Jos and Abeokuta, Nigeria and its Associated Cancer Risks(2012) Alausa, S. K.Ionizing radiations resulting from either natural or artificial radioactivity are useful but associated with them are health risks which increase with exposure. The natural radioactivity levels in soils of some locations in Jos and Abeokuta are significantly higher than the world average. Enhanced internal and external radiation exposures to man may result from physical presence in, and ingestion of food items grown in these areas. Scientific data are sparse on the radionuclide contents in food crops, farm soils and their radiological implications on the population. Therefore the aim of this study was to determine the radioactivity levels of 40K, 226Ra and 232Th in food crops and farm soils, and associated cancer risks in the population in the areas. A total of 243 food crop samples from 19 commonly grown types including acha, cowpea, cassava, cocoyam, Guinea corn, maize and yam; and 106 soils samples were randomly collected from 40 farm lands, 23 in Jos and 17 in Abeokuta, selected at random. The samples were air dried to constant mass, pulverized, sieved to pass 2mm mesh-size and sealed for 4 weeks to attain secular equilibrium. The activity concentration of the radionuclides were determined by counting each sample for 10 hours using a gamma-ray spectrometer comprising 76mm x 76mm NaI(TI) detector coupled to a multichannel analyzer. The effective dose rates due to ingestion of the food crops and outdoor effective dose rates due to farm soils were evaluated using the calculated activity concentrations and food consumption rates from Federal Office of Statistics, Nigeria. The risk of incurring cancer from radiation exposure were evaluated using carcinogenicity radionuclide slope factors by United States Environmental Protection Agency and the linear non-threshold radiation risk model, and compared with the International Commission on Radiological Protection (ICRP) recommended limits. Data were analyzed using descriptive statistics. The concentration of 40K, 226Ra and 232Th in food crops in Jos ranged from 8.7-1406.1, 2.1-85.5 and 2.6-89.8 Bqkg-1 respectively; whereas in Abeokuta the range was 38.2-1648.3, 2.1-81.1 and 2.6-48.3 Bqkg-1 respectively. The concentration of 40K, 226Ra and 232Th in farm soils were respectively 698.0±416.0; 143.1±80.8 and 287.3±306.3 in Jos and 411.0±341.0; 65.0±29.0 and 184.0±205.0Bqkg-1 in Abeokuta. The radioactivity levels were higher in Jos than Abeokuta. The tin mining in Jos might be the principal differential factor for its elevated radioactivity compared to Abeokuta. The annual average effective doses due to food ingestion in Jos was 0.20.01Sv (cowpea), 1852.0±43.1μSv (yam); in Abeokuta 58.7±15.7μSv (cocoyam) and 1064.6±32.2μSv (cassava). The average annual outdoor effective doses from farm soils were 0.430.32mSv for Jos and 0.210.18mSv for Abeokuta. The cancer risks due to farm soils and food ingestion were 1.42 x 10-2 and 8.57x10-3 for Jos and Abeokuta respectively. The effective doses were below the ICRP recommended limit of 1mSv and the cancer risks were slightly higher than the ICRP value of 1.0 x10-3. Cassava and yam had high radioactivity compared to other food crops. Radiological cancer risk among the population was high. The quantity of cassava and yam consumed from the areas should be reduced.Item Theoretical Determination of some Thermodynamic Properties of Selected Binary Liquid Alloys(2013) Odusote, Y. A.Binary liquid alloys have found wide applications in electronics, communications, automotive and aerospace technologies. The development of new alloys and improvement of existing ones require accurate knowledge of thermodynamic variables of the constituent systems which may not be obtainable experimentally. Hence, there is always the need for theoretical investigation to complement experiment. This study was aimed at theoretical determination of the thermodynamic properties of nine binary liquid alloys. Nine liquid alloys (Al-Zn, Bi-In, Ga-Zn, Ga-Mg, Al-Ga, Sb-Sn, In-Pb, Ga-Tl and Al-Si) with insufficient theoretical investigation were selected for investigation using three different models. Quasi-lattice theory which connects thermodynamic and dynamical properties was employed to determine the concentration concentration fluctuation in the long-wavelength limit [Scc(0)], chemical short range order parameter (α1), free energy of mixing (GM), the concentration dependence of diffusion and viscosity of Al-Zn and Bi-In liquid alloys. Quasi-chemical approximation model for strongly interacting systems was used to investigate ordering and glass formation tendencies in Ga-Zn, Ga-Mg and Al-Ga binary alloys. A statistical thermodynamic theory was used to determine the mixing properties of Sb-Sn, In-Pb, Ga-Tl and Al-Si liquid alloys. The choice of model was influenced by the type of available experimental data. The Scc(0) and α1 showed that a reasonable degree of chemical order existed in Bi-In system, while Al-Zn liquid alloys exhibited a liquid miscibility gap or phase separation at all concentrations. The values of free energy of mixing at the equiatomic composition were -0.4986RT and -0.9344RT for Al-Zn and Bi-In alloys respectively. The free energy of mixing of Ga-Zn, Al-Ga and Ga-Mg alloys are almost symmetrical around the equiatomic composition with Ga-Mg being the most interacting, while Al-Ga is more interacting than Ga-Zn alloy. Apart from Ga-Mg alloys with negative enthalpy of mixing, both the enthalpy of mixing and entropy of mixing of the three Ga-based systems are positive and symmetrical about the equiatomic composition. In the concentration range 0 ≤ cAl ≤ 0.3 and 0.7 ≤ cAl ≤ 1, Al-Ga systems exhibited a glass-forming potential. The free energy of mixing, enthalpy of mixing and entropy of mixing of Sb-Sn and Al-Si liquid alloys exhibited negative deviations from ideality and were symmetric around the equiatomic composition, while In-Pb and Ga-Tl systems exhibited positive deviations with Ga-Tl alloys showing asymmetry behaviour. The compound formation in liquid phase was weaker in Al-Zn than in Bi-In alloys. The Sb-Sn and Al-Si liquid alloys had tendency for heterocoordination, while In-Pb and Ga-Tl exhibited homocoodination. The Ga-Zn and Al-Ga alloys exhibited homocoordination, whereas Ga-Mg alloys had tendency towards heterocoodination.Item Assessment of Detrimental Health Effect of Radiation Associated with Diagnostic X-Ray Examinations at Four Centres in Nigeria(2011) Akinlade, B. I.Radiation exposure during diagnostic X-ray examinations has been widely reported as one of the sources of cancer induction. Information on X-ray machine and exposure parameters are crucial to risk assessment, which in turn are important for optimization of radiation protection measures. The documentation of radiation risk in Nigeria is sparse and hence the effectiveness of radiation protection measures at diagnostic centres has not been well established. This work was aimed at measuring effective dose received by patients during diagnostic x-ray examinations and estimating the associated risk. Between the years 2004 and 2006, the beam output of x-ray machines at four diagnostic centres with adequate regulatory activities were measured with non-invasive x-ray meter. These centres include University College Hospital (UCH) Ibadan, Twotees Diagnostic Centre (TDC) Ibadan, Obafemi Awolowo University Teaching Hospital Complex (OAUTHC) Ile-Ife and National Hospital Abuja (NHA). Field sizes, focus to skin distance (FSD), tube filtration, operating potential (kVp) and tube loading (mAs) were measured and used to calculate Dose Area Product (DAP) per patient. Data on age and examination type were recorded for 1034 patients which include 310(UCH), 276(TDC), 220(OAUTHC) and 228(NHA). These and calculated DAP were used to run Monte Carlo program to obtain effective dose. The risk of cancer was thereafter estimated using fatal cancer risk factor of 5 x 10-2 Sv-1. The results obtained were compared with the risk estimates recommended by the International Commission on Radiological Protection (ICRP). X-ray field sizes and FSD of the examinations considered ranged from 8 cm x 5 cm to 40 cm x 35 cm and 75 cm to 139 cm respectively. The tube filtrations (mmAl) at UCH, TDC, OAUTHC and NHA were 1.7, 2.7, 1.7 and 1.0 +1.0 mmCu respectively while the mean exposure parameters (kVp, mAs) were 69, 45; 76, 79; 100, 83; and 75, 28 respectively. Analysis of examination type showed that thoracic x-ray examination was the most common (74.0%). This was followed by head and neck (11.0%), pelvic (8.0%), lower limb (4.0%), abdomen (2.0%) and upper limb (1.0%). The mean age (years) of patients was 38±1 at UCH, 32±1 at TDC, 27±1 at OAUTHC and 28±1 at NHA. Examination procedures were the same in all centres except the use of anti-scatter grid for thoracic examination at OAUTHC. In all x-ray examinations, DAP (mGycm2) generally ranged from 70 to 38,155. The range of effective doses (mSv) at UCH, TDC, OAUTHC and NHA were 0.01–0.11, 0.01–0.17, 0.24–4.74 and 0.01–0.10 respectively while the corresponding estimated risks of cancer per million were 2–9, 2–22, 100–400 and 2-6. The values at OAUTHC were higher than ICRP risk estimates of 35 cancer cases per million. This was traceable to selection of high kVp with high mAs and insufficient tube filtration. Radiation risks associated with diagnostic X-ray examinations were within acceptable limit except at OAUTHC. For radiation risks to be within the recommended limit, the use of high kVp with low mAs and careful application of anti-scatter grid are encouraged.Item Move-Biased Monte Carlo Simulation Method for Protein Native Structure Prediction(2016) Aisida, S. O.Proteins are polymers of Amino Acid (AA) which are constructed after translation of genetic code 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 circumvent these challenges. However, the MC is complex and inconsistent in NS Prediction (NSP). This study was designed to develop a Move-Biased MC (MBMC) simulation algorithm that may simplify the complexity of existing MC and makes it consistent for NSP. Protein was described as a coarse-grained structure and folding as Self-Avoiding Walks (SAW) on square lattices. Relative Probability Parameters (RPP) were introduced to determine natural probabilities of protein conformations from SAW and to simulate the desired sequence length from 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-Biased (MB) on the lowest energy SAW conformation. The materials for testing the MBMC method included eight Benchmark Sequences (BMS) from the protein data bank 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 nm, 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 algorithm were 0.71, 0.02, 0.25 and 0.02 for up, down, left and right orientations, respectively. The energies of the NS obtained from the MBMC method were -9, -9, -8, -14, -23, -35, -42 and -52 J for the BMS, respectively. In contrast, for GA energies derived 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 they were -9, -9, -8, -14, -23, -35, -39 and -52; for ENA they were -9, -9, -8, -14, -23, -36, -39, and no record for eighth BMS; 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, 9.46, 9.52, and 12.85 seconds, respectively. In contrast the computation times for GA were only reported for the first four BMS as 5.60, 6.00, 3.66, 54.60 seconds, and no record of computational time for the CMC and EMC Benchmark sequences, respectively. Moreover, MBMC has fewer algorithmic steps and simpler simulation procedure than CMC, GA, EMC and ENA methods. The developed Move-Biased Monte Carlo method had simpler algorithmic steps than the existing Monte Carlo methods and consistently predicted the native structure of proteins faster than existing algorithms.