No abstract

The objective of this study is to analyze the efficiency of different antennas proposed for microwave ablation therapy using numerical simulation and experimental approach. The simulation was done with COMSOL MULTIPHYSICS Ò software to design antenna prototypes and evaluate its reflection coefficient, power dissipation distribution, power dissipation density, specific absorption rate and temperature distribution in tissue. Antennas were fabricated from a 50 X RG405/U semi-rigid coaxial cable to match the geometric prototypes generated during simulation. Ex vivo bovine livers were ablated with the fabricated antennas using 50 W for 5 and 10 min. Ablation diameters, ablation lengths and aspect ratios were determined. Sleeved antenna produced lowest reflection coefficient, high power dissipation, low power dissipation density, high SAR and high temperature in the simulation. Sleeved antenna provides excellent localization, large ablative diameter, low backward heating and high aspect ratio than single slot, dual slot and monopole antennas.

In the industrialized area of Lagos, vegetables are mostly cultivated through surface water irrigation. Untreated surface water has the potential of being contaminated with radionuclides from industrial effluents. This study evaluated the concentration of radionuclides in the leafy vegetables cultivated through surface water irrigation in Lagos metropolis and the potential health risks associated with their consumption. The specific activities of 226 Ra, 232 Th and 40 K in some commonly consumed leafy vegetables were determined using High Purity Germanium (HPGe) detector. To assess the radiation hazards associated with the consumption of these vegetables, annual effective dose (AED) and excess lifetime cancer risk (ELCR) were also determined. The specific activities of 226 Ra, 232 Th and 40 K in the investigated samples ranged from 0.49±044 to 6.00±1.19 Bq/kg, with an average value of 2.08±0.59 Bq/ for 226 Ra, from 0.10±0.07 to 0.61±0.12 Bq/kg with an average value of 0.85 ±0.08 Bq/kg for 232 Th and from 28.69±3.09 to 126.71±5.86 Bq/kg with an average value of 72.56±5.36 Bq/kg for 40 K. The mean activities of 226 Ra and 232 Th were 40 and 56 times higher than the World Health Organization (WHO) reference values for 226 Ra and 232 Th in leafy vegetables respectively. The AED estimated from the consumption of vegetables was 0.048 mSv/y, which is about 16 % of the reference AED value for radionuclides of natural origin in the total diet while leafy vegetable represents about 8 % of the total diet of an adult in Lagos. The ELCR obtained from this study was this is lower than the world's average value. This study has found elevated concentrations of 226 Ra and 232 Th in leafy vegetables, and noticeable increase in AED associated with 226 Ra exposure in the consumption of leafy vegetables cultivated in Lagos. There are therefore potential radiological health risks to the health of the public from long-term consumption of leafy vegetables cultivated through surface water irrigation in Lagos, Nigeria.

No abstract

respectively. The radon concentration for location 10 in Ono-Ara local government exceeded the recommended limit. However, the overall average indoor radon concentration of the three local governments was found to be lower than the world average value of 40 Bqm -3. Hence, there is need for proper awareness about the danger of radon accumulation in dwelling places.