Easy Determination of Radiation Absorption in Brain Tissue from Mobile Phones Using Finite Element Method

Brain tissue plays a significant role in both cognitive and psychomotor behavior of humans. However, their interaction with radiation emanating from hand held mobile devices is still not fully understood. This research was aimed at investigating radiation absorption in brain tissue. Bovine brain tissues ranging from lesser than 1 year to greater than 10 years of age were bought from a specialty store (Sigma-Aldrich). The tissues were used within 72 h of extraction for ex vivo brain experiments. The brain tissue was stored at 6°C and then 16°C for 24 h in the MRI room to reach thermal equilibrium before any experiments were undertaken. The averages for the dielectric constant were measured from 1 - 4 GHz using open ended coaxial probe (OECP) (85,070E;Agilent Technologies). The results obtained for the dielectric properties were then used as raw data in the numerical computation and simulation of the radiation absorption by the brain tissues for both adolescent and adults bovine brain tissue using finite element method (FEM). The measured dielectric constants varied for the different brain tissue from 54.39 to 39.29. Analysis showed that adolescents tissue absorbed more radiation than adults from mobile phoneradiation which is due to the higher dielectric property of adolescent brain tissue. The results obtained can be applied to human brain tissue since bovine shares the same compositional properties with humans.

Effect of Sintering Temperature on Co<SUB>0.5</SUB>Zn<SUB>0.5</SUB>Fe<SUB>2</SUB>O<SUB>4</SUB>Nano-Particles Evolution and Particle Size Distribution

This study involves an investigation to ascertain the effect of sintering temperature on the particle size distribution of Co0.5 Zn0.5 Fe2O4 nano-particle. The effect of the sintering temperature towards diffusion of CoO and ZnO into the tetrahedral and octahedral sites was also reported. In this study, CoO, ZnO and Fe2O3 powders were mechanically alloyed to synthesize fine powders of Co0.5 Zn0.5 Fe2O4 nano-particles. The synthesized powder was then sintered at various temperatures which were employed to study the effect of sintering temperature on the materials. Further analysis was done using XRD to investigate the phases of the powder and the crystallite size using Scherrer equation, SEM and EDX for the morphology and elemental composition of samples. The XRD spectra indicated that Both ZnO and CoO powder reacted well during sintering, however, ZnO was first to diffuse into its crystallographic sites before CoO. While the particle size distribution increases as the sintering temperature increases. Amongst other findings, it was confirmed that sintering temperature affects the particle size distribution of samples and samples begin to agglomerate at temperature above 700°C.

Effect of Milling Time on Co<SUB>0.5</SUB>Zn<SUB>0.5</SUB>Fe<SUB>2</SUB>O<SUB>4</SUB>Microstructure and Particles Size Evolution via the Mechanical Alloying Method

Nanocrystalline CoZn-ferrite was fabricated by a high-energy milling method by mixing Fe3O4+CoO+ZnO. The structural properties of the milled powder at different milling times were analysed so to ascertain the diffusion of CoO and ZnO into the tetrahedral and octahedral sites using mechanical alloying method. The effect of mechanical alloying towards particle size was also investigated. The XRD spectra indicated the precursors reacted during milling with the diffusion of ZnO and followed by CoO into their respective crystallographic sites. SEM micrographs showed the agglomeration of powders due to high energy milling and TEM images confirmed that the particles of the materials were of nanosize dimension. In addition, the results show that the grain possesses a single-phase CoZn-ferrite structure in a typical size of ~16–30 nm. The experiment reveals that nanosize CoZn-ferrite can be obtained after the powder is milled for about 8 hours at room temperature. The mechanism and efficiency of the synthesis of the technique are also discussed in this paper.

Experimental and Computational Study of the Microwave Absorption Properties of Recycled α-Fe2O3/OPEFB Fiber/PCL Multi-Layered Composites

The aim of this study was to fabricate multi-layered recycled α-Fe2O3/OPEFB fiber/PCL composites for microwave absorbing applications in the 1 - 4 GHz frequency range. The multi-layered composites were 6 mm thick and each consisted of a 2 mm thick layer of recycled α-Fe2O3/PCL composites at various loadings (5 wt% - 25 wt%) of 16.2 nm recycled α-Fe2O3 nanofiller, placed between two layers of 2 mm thick OPEFB fiber/PCL composites blended at a fixed ratio of 7:3. The real (ε') and imaginary (ε") components of the relative complex permittivity were measured using the open-ended coaxial probe technique and the values obtained were applied as inputs for the Finite Element Method to calculate the reflection coefficient magnitudes from which the reflection loss (RL) properties were determined. Both ε' and ε" increased linearly with recycled α-Fe2O3 nanofiller content and the values of ε' varied between 3.0 and 3.9 while the ε" values ranged between 0.26 and 0.64 within 1 - 4 GHz. The RL (dB) showed the most prominent values within the 1.38 - 1.46 GHz band with a minimum of -38 dB attained by the 25 wt% composite. Another batch of minimum values occurred in the 2.39 - 3.49 GHz range with the lowest of -25 dB at 2.8 GHz. The recycled α-Fe2O3/OPEFB fiber/PCL multi-layered composites are promising materials that can be engineered for solving noise problems in the 1 - 4 GHz range.

Permittivity models for determination of moisture content in Hevea Rubber Latex

The commercial open-ended coaxial probe(Agilent 85070E)is the most commonly used sensor to determine the permittivity of wet materials.This paper extends the usability and applicability of the sensor to the estimation of moisture content in Hevea Rubber Latex.The dielectric constant and loss factor were measured using the commercial probe whilst the moisture contents were obtained using the standard oven drying method.Comparison results were obtained between the different dielectric models to predict moisture content in latex.Both the dielectric constant and the loss factor of rubber latex linearly increased with moisture content at all selected frequencies.Calibration equations were established to relate both the dielectric constant and the loss factor with moisture content.These equations were used to predict moisture content in Hevea latex from measured values of the dielectric constant and the loss factor.The lowest mean relative error between actual and predicted moisture contents was 0.02 at 1 GHz when using the Cole-Cole dielectric constant calibration equation.