Atmospheric concentrations of 7Be and 212Pb were measured for 11 years (2008 – 2018) in Dar es Salaam, Tanzania. The mean activity concentrations of 7Be and 212Pb were found to be within the range of 1.29 – 5.71 mBq/m3 and 10.85 – 50.06... more
Atmospheric concentrations of 7Be and 212Pb were measured for 11 years (2008 – 2018) in Dar es Salaam, Tanzania. The mean activity concentrations of 7Be and 212Pb were found to be within the range of 1.29 – 5.71 mBq/m3 and 10.85 – 50.06 mBq/m3, respectively. The annual mean activity concentrations of 7Be and 212Pb were 4.72 ± 1.18 mBq/m3 and 29.76 ± 13.63 mBq/m3, respectively. Distinct annual trends were depicted on 7Be and 212Pb, suggesting that the two radionuclides were affected differently with atmospheric conditions. Monthly atmospheric concentrations of 7Be showed a strong seasonal variation trend with the highest in January and February and lowest in April. 212Pb depicted the highest concentration during June and July and lowest in January and December. The regression analysis for 7Be and 212Pb activity concentrations together with number of meteorological parameters revealed that the relative humidity, rainfall, air temperature, absolute humidity and wind speed are the most ...
Atmospheric concentrations of 7Be and 212Pb were measured for 11 years (2008 – 2018) in Dar es Salaam, Tanzania. The mean activity concentrations of 7Be and 212Pb were found to be within the range of 1.29 – 5.71 mBq/m3 and 10.85 – 50.06... more
Atmospheric concentrations of 7Be and 212Pb were measured for 11 years (2008 – 2018) in Dar es Salaam, Tanzania. The mean activity concentrations of 7Be and 212Pb were found to be within the range of 1.29 – 5.71 mBq/m3 and 10.85 – 50.06 mBq/m3, respectively. The annual mean activity concentrations of 7Be and 212Pb were 4.72 ± 1.18 mBq/m3 and 29.76 ± 13.63 mBq/m3, respectively. Distinct annual trends were depicted on 7Be and 212Pb, suggesting that the two radionuclides were affected differently with atmospheric conditions. Monthly atmospheric concentrations of 7Be showed a strong seasonal variation trend with the highest in January and February and lowest in April. 212Pb depicted the highest concentration during June and July and lowest in January and December. The regression analysis for 7Be and 212Pb activity concentrations together with number of meteorological parameters revealed that the relative humidity, rainfall, air temperature, absolute humidity and wind speed are the most ...
An experiment was conducted to study the performance of thallium doped sodium iodide (NaI(Tl)) scintillators in measuring the lifetimes of nuclear excited states that are just above 1 ns. A bench top setup with two similar NaI(Tl)... more
An experiment was conducted to study the performance of thallium doped sodium iodide (NaI(Tl)) scintillators in measuring the lifetimes of nuclear excited states that are just above 1 ns. A bench top setup with two similar NaI(Tl) detectors was used to measure the lifetime of Yrast I π = 2 + state in 152 Sm via γ – γ coincidences. Results showed high precision of the timing system used and the accuracy of measurement confirming the suitability of NaI(Tl) scintillators in measuring lifetimes longer than 1 ns.
The purpose of this study was to simulate the GSO detector of a micro PET using GATE simulation platform. The performance and responses of the simulated GSO detector assembly were evaluated by comparing the simulated data to the... more
The purpose of this study was to simulate the GSO detector of a micro PET using GATE simulation platform. The performance and responses of the simulated GSO detector assembly were evaluated by comparing the simulated data to the experimental and XCOM data to validate the simulation platform and procedure. Based on NEMA NU-4 2008 protocols, the performance of GSO detector in terms of sensitivity was simulated and compared to the experimental data. Similarly, the GSO detector response to photons interaction was simulated and compared against the XCOM data for absorbed intensity ratio in the GSO detector and survived intensity ratio in Pb blocks. Results showed that simulated and experimental sensitivities agreed well with R2 of 0.995 and two overlapping bands at 95% confidence. An agreement with R2 of 0.972 and 0.973 as well as with overlapping bands at 95% confidence was obtained in simulated and XCOM data for absorbed and survived intensity ratio in the GSO detector and Pb blocks, r...
Soft tissue imaging is heavily impaired by streaks and cupping effects associated with X-ray scatter. Quality of images from projection imaging may be improved by the use of enhanced antiscatter grids’ designs with potency to reject... more
Soft tissue imaging is heavily impaired by streaks and cupping effects associated with X-ray scatter. Quality of images from projection imaging may be improved by the use of enhanced antiscatter grids’ designs with potency to reject significant scatter. However, optimization of grid characteristics requires investigation to improve diagnostic image quality. Transmitted scatter spatially distributed degrades images engendering need for effective scatter correction protocols. This study investigated the pre-scan scatter suppression algorithm for X-ray exposure of soft tissue equivalent phantoms over nominal energy range. Adipose tissue and polymethyl methacrylate phantoms of cross-sectional area (30 x 30) cm 2 and of varying thickness from 2 to 8 cm in 1 cm increments were successively exposed using energy ranging between 20–50 kVp. Monte Carlo simulation based on FLUKA code and flair interface was used to generate an input file for execution. The source simulated five cycles of ten m...
Salt from Bahi wetlands is allegedly containing high concentrations of heavy metals since the wetlands are in the proximity of the prospective uranium mining sites. This means Bahi salt could be an important route through which salt... more
Salt from Bahi wetlands is allegedly containing high concentrations of heavy metals since the wetlands are in the proximity of the prospective uranium mining sites. This means Bahi salt could be an important route through which salt consumers are exposed to high concentrations of heavy metals. This study has analysed 50 salt samples of Bahi salt in order to determine the concentrations of both heavy metals and essential elements using the Energy Dispersive X-Ray Fluorescence Spectrometry (EDXRF). Analytical results show that apart from Na and Cl, Bahi salt is composed of several elements including heavy metals such as Cr, Cd, Pb, Th and U. The salt also contains essential elements such as Mg, K, Ca, Mn, Fe, Co, Zn and Br. The mean concentrations of Cr, Cd, Pb, Th and U ranged from 20 - 25μg/g, 3.8 – 8.85 μg/g, 2.29 – 5.8 μg/g, 6.22 – 15.8 μg/g and 6.5 – 9.12 μg/g respectively. All these toxic elements were in higher concentrations than the recommended maximum tolerable limits (MTL)....
High-energy bremsstrahlung photon emission beyond a critical energy from electron cyclotron resonance (ECR) heating has long attracted much attention, and its nature has yet been unsolved. We have measured bremsstrahlung photons from the... more
High-energy bremsstrahlung photon emission beyond a critical energy from electron cyclotron resonance (ECR) heating has long attracted much attention, and its nature has yet been unsolved. We have measured bremsstrahlung photons from the 28-GHz ECR ion source at Busan Center of Korean Basic Science Institute. The gamma-ray detection system consists of three NaI(Tl) scintillation detectors placed 62 cm radially from the beam axis and a NaI(Tl) scintillation detector at the extraction port for monitoring the photon intensity along the beam axis. Bremsstrahlung photon energy spectra were measured at nine azimuthal angles at the RF power of 1 kW. Azimuthal angular distributions of bremsstrahlung photons were found to be in coincidence with the structure the ECR ion source and the shape of ECR plasma.
Background: Projection diagnostic X-ray images are inherently affected by the masking effects of transmitted scatter. Spatially distributed transmitted scatter degrades image quality engendering need for effective scatter correction... more
Background: Projection diagnostic X-ray images are inherently affected by the masking effects of transmitted scatter. Spatially distributed transmitted scatter degrades image quality engendering need for effective scatter correction protocol. Objectives: To investigate origin of scatter components transmitted through anti-scatter grids to the detector of digital radiographysystem using Monte Carlo simulation. Methods: Over 107 photons were exposed through the reconstructed MC simulation phantom. Transmitted photons (primary and scatter) were scored as fluence, dose and deposited energy. Scatter components were investigated analytically over varying phantom thickness, tube kV and grid characteristics. Test disks were exposed as ROI embedded in phantom to evaluate the potential contrast improvement in image quality with the proposed technique. Results: Simulated and experimental results were comparable and in agreement with literature. SPR and SF mean values of 10.5, 0.314 and 7.96, 0...
CZTS thin films were deposited by sol–gel spin coating method using precursor solutions prepared by dissolving copper acetate dihydrate, zinc acetate dihydrate, tin chloride and thiourea in methanol and monoethylamine then annealed in RTP... more
CZTS thin films were deposited by sol–gel spin coating method using precursor solutions prepared by dissolving copper acetate dihydrate, zinc acetate dihydrate, tin chloride and thiourea in methanol and monoethylamine then annealed in RTP furnace at 500 °C. Sol–gel precursor solutions were prepared with different Zn/Sn in a precursor solution and were annealed at different time intervals; and their effects on the optical and electrical properties of CZTS (Cu2ZnSnS4) films were investigated. The optical band-gap values were estimated to be between 1.30 and 1.88 eV while the absorption coefficients were in the range of 104 cm–1 in the visible region. The resistivity and carrier concentrations ranged from 13.12 to 2634 kΩ/□ and 1017 to 1020 cm−3,respectively. The influence of Zn/Sn ratio and annealing time on structural properties of CZTS thin films are also discussed.Keywords: CZTS; Cu2ZnSnS4; Kesterite; Zn/Sn rati
In this thesis three techniques, namely, X-ray Fluorescence, X-ray diffraction and Moessbauer spectroscopy were used to study the effects of impurities on the structural and magnetic properties of natural iron sulphides from the Lake... more
In this thesis three techniques, namely, X-ray Fluorescence, X-ray diffraction and Moessbauer spectroscopy were used to study the effects of impurities on the structural and magnetic properties of natural iron sulphides from the Lake Victoria gold field. Pyrite and pyrrhotite being the main component of the iron sulphide in this area were investigated.
