Specific Absorption Rate Values Research Articles

Radiation effect of M-slot patch antenna for wireless application

Today, the specific absorption rate has become an important and necessary measurement when designing and implementing any type of antenna. In recent years, various devices have appeared that use different frequencies for wireless communication systems, which are a source of electromagnetic radiation. The M-slot antenna is designed in this paper to operate in multi-band frequencies for wireless communications using computer simulation technology (CST) software 2020. The radiation effect for this antenna is calculated for tissue mass of the human fingertips, which consists of three layers (skin, meat, and bone), over a mass of 1 g and 10 g according to the IEEE and International Commission on Non-Ionizing Radiation Protection (ICNIRP) organization. The results are shown three applications in the communication system, which are Wi-Fi, worldwide interoperability for microwave access (Wi-Max) and, satellite X-band and, the value of specific absorption rate (SAR) increase with increased frequency.

Novel implantable antenna with miniaturized footprint size for wideband biomedical telemetry applications

Abstract Medical telemetry applications rely heavily on biomedical implanted antennas. These biomedical implanted devices can enhance and monitor patients’ daily life circumstances. A low-profile, downsized size implanted antenna operating at 915 MHz in the industrial, scientific, and medical (ISM) band is suggested in this research. The antenna is a simple slotted patch supplied by a 50-impedance coaxial probe. The radiator is made up of two slotted parasitic patches with one square-shaped outer radiator are manufactured on a Roger Droid RT5880 substrate with a standard height of 0.254 mm (ε r = 2.2, tanδ = 0.0009). The entire dimension of the given antenna is 11 × 11 × 0.2514 mm with an electrical size of 0.049λ g × 0.049λ g × 0.0011λ g. The antenna spans a bandwidth of 0.82–1.05 GHz when working inside muscle tissues (25.13 percent). The antenna’s calculations and experimental findings are quite similar. The computed specific absorption rate (SAR) values inside muscle of above 1 g mass tissue are 7.25 W/kg, according to the data. The stated SAR values are lower than the limit set by the Federal Communications Commission (FCC). As a result, the proposed small antenna is a strong contender for biological implantable applications.

Development of a Numerical Tablet Model in WLAN Band for SAR Study

This research proposes a numerical model for a tablet in the wireless local area network band for specific absorption rate (SAR) study. The design criteria, such as the tablet size, operating frequencies, antenna position, and target 1-g peak spatial-average SAR (psSAR) values in the flat phantom, are determined based on the SAR test reports of tablets distributed in South Korea from 2013 to 2017. An internal antenna is designed in a tablet platform to operate in dual bands of 2,450 MHz and 5,500 MHz. The numerical results illustrate that the 1-g psSAR values of the proposed numerical tablet model are within ±10% of the target values. Moreover, the return loss of the designed tablet model is larger than 10 dB, regardless of flat phantom, while its radiation efficiency is higher than 90% in free space.

A Novel Approach of a Low-Cost UWB Microwave Imaging System with High Resolution Based on SAR and a New Fast Reconstruction Algorithm for Early-Stage Breast Cancer Detection.

In this article, a new efficient and robust approach—the high-resolution microwave imaging system—for early breast cancer diagnosis is presented. The core concept of the proposed approach is to employ a combination of a newly proposed delay-and-sum (DAS) algorithm and the specific absorption rate (SAR) parameter to provide high image quality of breast tumors, along with fast image processing. The new algorithm enhances the tumor response by altering the parameter referring to the distance between the antenna and the tumor in the conventional DAS matrices. This adjustment entails a much clearer reconstructed image with short processing time. To achieve these aims, a high directional Vivaldi antenna is applied around a simulated hemispherical breast model with an embedded tumor. The detection of the tumor is carried out by calculating the maximum value of SAR inside the breast model. Consequently, the antenna position is relocated near the tumor region and is moved to nine positions in a trajectory path, leading to a shorter propagation distance in the image-creation process. At each position, the breast model is illuminated with short pulses of low power waves, and the back-scattered signals are recorded to produce a two-dimensional image of the scanned breast. Several simulations of testing scenarios for reconstruction imaging are investigated. These simulations involve different tumor sizes and materials. The influence of the number of antennas on the reconstructed images is also examined. Compared with the results from the conventional DAS, the proposed technique significantly improves the quality of the reconstructed images, and it detects and localizes the cancer inside the breast with high quality in a fast computing time, employing fewer antennas.

Cytotoxic effect of functionalized superparamagnetic samarium doped iron oxide nanoparticles for hyperthermia application

Magnetic Fluid Hyperthermia (MFH) is an emerging and safe technique for cancer treatment. Radiotherapy and Chemotherapy are widely adopted techniques for treating cancer but cause damage to the nearby healthy tissue. This paves the way for hyperthermia treatment for cancer. Since healthy cells are more heat-tolerant than malignant cells, magnetic nanoparticles with superparamagnetic properties were used in hyperthermia treatment. Surface modified magnetite (Fe3O4) iron oxide nanoparticles with enhanced stability, solubility, bio-compatibility and magnetic property were employed in hyperthermia treatment. In the present study, Superparamagnetic Samarium doped magnetite (Fe3O4:Sm) nanoparticles were functionalized with Oleylamine (OAm) and polyvinyl alcohol (PVA) by the sol-gel process. The obtained nanoparticles were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and UV–Visible diffuse reflectance spectroscopy (UV-DRS), Thermogravimetric analysis (TGA) and Vibrating Sample Magnetometer (VSM). From XRD data, the crystallite size of oleylamine coated samarium doped magnetite (OAm–Fe3O4:Sm) and PVA-coated samarium doped Fe3O4 (PVA- Fe3O4:Sm) were found to be 9.5 nm and 10.9 nm, respectively. TEM images of the functionalized nanoparticles were visualized as a spherical structure with reduced agglomeration. UV-DRS gives the bandgap value of OAm–Fe3O4:Sm and PVA- Fe3O4:Sm coated samarium doped magnetite to be 2.3 eV and 2 eV respectively. VSM measurement of OAm-Fe3O4:Sm and PVA- Fe3O4:Sm coated, showed superparamagnetic behaviour. The cytotoxicity study on the L929 cell line shows that both oleylamine and PVA-coated samarium doped magnetite were less toxic and biocompatible compared to the uncoated Fe3O4:Sm. The hyperthermia study reveals a rise in temperature within a few seconds with a high Specific Absorption Rate (SAR) value, confirming that the functionalized Samarium doped Fe3O4 was an effective nanomaterial for hyperthermia application.

Use of Mobile Phones in Patients with Stroke

Objectives: There is a paucity of systematic studies conducted to get information on the impact of mobile phone radiation on health. This pilot study was done to explore the use of mobile phones in patients with stroke. Methods: This cross-sectional study used a structured questionnaire among stroke patients in a tertiary hospital in India. We collected demographic details, history, and information on their mobile phone type, usage, and specific absorption rate (SAR) value. We used descriptive statistics to report our findings. Results: This group of 50 stroke patients was predominantly an urban population (78%) with a higher number of male subjects (56%); a higher prevalence of ischemic stroke (76%); 30% were smokers; with comorbidities of hypertension (75%) and diabetes (46%), a significant proportion of whom were not on regular treatment 64% and 74%, respectively. More number of patients used feature phones (82%). The median (SAR) value of all phones was 0.81 W/kg. Hypertension was present in patients who had contact with the phone for >5 hours (78%), subjects who kept their phone closer to the pillow while sleeping (71%), and those carrying a phone in their pockets or on self for >5 hours (80%). Conclusion: This group of patients had predominantly ischemic stroke; a significant proportion having hypertension and diabetes were not on regular treatment and were smokers. Cases of hypertension were noted to be higher in patients with increased exposure to mobile phone radiation. As a pilot study with limitations of a small number of patients, these findings could be only incidental. Further research is required to make any conclusions.

Design of functionalized magnetic silica multi-core composite nanoparticles for synergistic magnetic hyperthermia/radiotherapy in cancer cells

Nanomaterials in particular the magnetic nanoparticles (MNPs) offer tremendous potential for cancer treatment due to their unique intrinsic properties. Combining materials with a variety of functional groups, and forming a multifunctional nanosystem to overcome the limitations of monotherapy for cancer treatment has always been a research focus with notable difficulties. Considering the many challenges faced by radiotherapy and hyperthermia, in this study, we designed a rational strategy for magnetic hyperthermia using Fe3O4@SiO2@Sec2@FA nanoparticles as a novel nano-radiosensitizer to simultaneously enhance the therapeutic effects of radiotherapy in the future. Fe3O4@SiO2 core–shell structured nanoparticles were synthesized with an appropriate silica layer thickness to maintain good saturation magnetization. The as-prepared Fe3O4@SiO2@Sec2@FA nanoparticles had the specific absorption rate (SAR)value of 57 W/g, which was below the clinically acceptable alternating magnetic field value of 4.9 × 109 Am−1s−1, indicating good heat generation efficiency (the temperature level ΔT=6–10 °C). Moreover, Folate-modified nanoparticles exhibited approximately 6-fold higher cellular internalization of Hela cells with no obvious cytotoxicity for the Hela and MDA-MB-231 cells, and lower cytotoxicity for the HUVECs in a concentration range of 0–150 µg/mL. In addition, these nanoparticles were modified on the silica surface by L-selenocystine, which could enhance the elimination of tumor cells by producing reactive oxygen species under X-rays, resulting in a novel radiosensitization effect. Therefore, the as-prepared Fe3O4@SiO2@Sec2@FA nanoparticles with good biocompatibility and active targeting would possess synergistic magnetic hyperthermia/radiotherapy effect.

A novel SAR reduction technique for implantable antenna using conformal absorber metasurface.

In this paper, a conformal absorber metasurface has been designed and used for reducing the specific absorption rate (SAR) of an implantable antenna. SAR reduction of implantable antennas is one of the significant design aspects to be considered for their use in modern-day healthcare applications. The introduction of the absorber metasurface restricts the back radiation of the antenna to control the SAR value. This technique decreases the maximum SAR value by 24% and also reduces the average SAR distribution significantly without affecting the desired antenna gain. A reduction in SAR value indicates the decrease in radiation absorption by human tissue, and thus, decreases the possibility of health hazards due to EM radiation. Later, this antenna-absorber system is designed as a capsule module for increased mobility and less-invasiveness. The redundancy of invasive surgery increases acceptance of the capsule module designs of implantable antennas and devices for various biomedical usages. In vitro testing of the fabricated prototype has been carried out inside a multi-layer porcine slab to verify the effectiveness of this unique SAR reduction technique.

Albumin Stabilized Fe@C Core-Shell Nanoparticles as Candidates for Magnetic Hyperthermia Therapy.

Carbon-encapsulated iron nanoparticles (Fe@C) with a mean diameter of 15 nm have been synthesized using evaporation–condensation flow–levitation method by the direct iron-carbon gas-phase reaction at high temperatures. Further, Fe@C were stabilized with bovine serum albumin (BSA) coating, and their electromagnetic properties were evaluated to test their performance in magnetic hyperthermia therapy (MHT) through a specific absorption rate (SAR). Heat generation was observed at different Fe@C concentrations (1, 2.5, and 5 mg/mL) when applied 331 kHz and 60 kA/m of an alternating magnetic field, resulting in SAR values of 437.64, 129.36, and 50.4 W/g for each concentration, respectively. Having such high SAR values at low concentrations, obtained material is ideal for use in MHT.

Engineering Gold Shelled Nanomagnets for Pre-Setting the Operating Temperature for Magnetic Hyperthermia.

This study investigated the fabrication of spherical gold shelled maghemite nanoparticles for use in magnetic hyperthermia (MHT) assays. A maghemite core (14 ± 3 nm) was used to fabricate two samples with different gold thicknesses, which presented gold (g)/maghemite (m) content ratios of 0.0376 and 0.0752. The samples were tested in MHT assays (temperature versus time) with varying frequencies (100–650 kHz) and field amplitudes (9–25 mT). The asymptotic temperatures () of the aqueous suspensions (40 mg Fe/mL) were found to be in the range of 59–77 °C (naked maghemite), 44–58 °C () and 33–51 °C (). The MHT data revealed that could be successful controlled using the gold thickness and cover the range for cell apoptosis, thereby providing a new strategy for the safe use of MHT in practice. The highest SAR (specific absorption rate) value was achieved (75 kW/kg) using the thinner gold shell layer (334 kHz, 17 mT) and was roughly twenty times bigger than the best SAR value that has been reported for similar structures. Moreover, the time that was required to achieve could be modeled by changing the thermal conductivity of the shell layer and/or the shape/size of the structure. The MHT assays were pioneeringly modeled using a derived equation that was analytically identical to the Box–Lucas method (which was reported as phenomenological).

Design of Antenna-Multiplexer for Seamless On-Body Internet of Medical Things (IoMT) Connectivity

Here, a compact design of antenna-multiplexer is engineered specifically to meet the stringent requirement imposed by intricate subsystems operating at 5.2, 5.5, and 5.8 GHz frequency bands for Internet of Medical Things (IoMT) applications. The proposed design includes a hexagonal-shaped substrate integrated waveguide (HSIW) cavity, tripole-shaped radiating slot, tuning vias, and three inset microstrip feedlines. A tripole-shaped slot is imprinted on the top of the SIW. This slot subdivides the cavity into trio-radiating segments and each segment offers a single frequency band. Further, the frequency bands are tuned at 5.2/5.5/5.8 GHz. The design maintains mutual port isolation better than 23.9 dB. Compared with the conventional tri-frequency antennas, the proposed design is highly compact and doesn’t need any additional circuitry to improve the port isolations. The measured results confirm the expected performance of the design. Furthermore, the proposed antenna is optimized within an implantable medical device (IMD) and simulated inside a realistic Human Head model at a depth of 3 mm and the Specific Absorption Rate (SAR) value is estimated. The SAR values are well below 0.362 W/Kg at the functioning bands due to the unidirectional radiation pattern from the antenna.

Green Synthesis of Magnetic Ferrites (Fe3O4, CoFe2O4, and NiFe2O4) Stabilized by Aloe Vera Extract for Cancer Hyperthermia Activities

The magnetic nanoferrites (Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , CoFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , and NiFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) were synthesized via hydrothermal method using an aloe vera plant extract solution. Magnetic nanoferrites were characterized using X-ray powder diffraction (XRD), vibrating sample magnetometer (VSM), field emission electron microscope (FESEM), transmission electron microscopy (TEM), and X-ray photon spectroscopy (XPS). Cytotoxicity was obtained using the water-soluble tetrazolium salt (WST) assay. X-ray diffraction analysis also demonstrated that the size range of the nanoferrites exhibited average diameters of 6–28 nm and also exhibited high crystallinity. Results showed that all the metallic nanoparticles (NPs) are magnetic with saturation values of Fe = 52 emu/g, Co = 33 emu/g, and Ni = 20.43 emu/g. The magnetic nanoferrites exhibited a high cell viability rate at high concentrations and as shown from the optical images of the cells signifies their nontoxic and biocompatibility property. From SEM and TEM, the spherical structure was noticeable and the particle size is also in accordance with XRD. The chemical states for each NP also confirmed the successful synthesis of each nanoferrite. Not to mention, the heating capabilities of the nanoferrites were investigated and showed significant temperature increase of 6 °C–8 °C and acceptable specific absorption rate (SAR) values. Interestingly, the results assure that the materials would be suitable as magnetic mediators for magnetic hyperthermia application for cancer treatment.

Dual-Mode Patch Antenna With Capacitive Coupling Structure for On-/Off-Body Applications

A dual-band dual-mode antenna for on-/off-body centric communications is proposed for 2.4 and 5.8 GHz industrial scientific medical bands. Using polydimethylsiloxane as substrate, the proposed antenna has a compact structure and is easy to wear. The on-body mode is realized by a circular patch loaded with four symmetrically distributed metallic vias to generate TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{\mathbf{01}}$</tex-math></inline-formula> mode located on the lower substrate. The off-body mode is achieved by a smaller circular patch on the top of the upper substrate, which generates a directional radiation pattern by exciting its TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{\mathbf{11}}$</tex-math></inline-formula> mode. The measured operating bandwidths of the proposed antenna in two bands are 90 MHz (2.40–2.49 GHz) and 330 MHz (5.63–5.96 GHz), respectively. Average gain for the on-body mode is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 2.38 dBi and for the off-body mode is 6.67 dBi. In addition, the antenna exhibits a robust performance near human tissue and low specific absorption rate values.

A Miniaturized Implantable Antenna for Wireless Power Transfer and Communication in Biomedical Applications

A miniaturized, triple-band, implantable antenna for biomedical applications is presented in this paper. The proposed antenna with dimensions of 8.1 mm × 8.1 mm × 0.64 mm, combined with a shorting pin and a ground slot, operates at bands between 401–406 MHz for the medical implant communications service (MICS); 1,395–1,400 MHz and 1,427–1,432 MHz for the wireless medical telemetry service (WMTS); and 2,400–2,500 MHz for industrial, scientific, and medical (ISM) applications. The antenna is deployed simultaneously for data transmission and wireless power transfer (WPT) at the two frequencies of communications and the ISM band, respectively. The antenna achieves peak gain values of -35.7 dBi, -25.1 dBi, and -19.5 dBi with the impedance bandwidths of 10.1%, 15.5%, and 9.58% at 402 MHz, 1.4 GHz, and 2.45 GHz, respectively. The experiments in the muscle tissue were implemented to demonstrate the reliability of the proposed antenna. To ensure safety standards in the human body environment, the specific absorption rate (SAR) value is simulated and evaluated thoroughly.

EFFECTS OF RADIATION FROM MOBILE PHONES ON FERTILITY AND THE QUALITY OF SEMEN IN REGULAR MOBILE PHONE USERS

Objective: The use of mobile phones over extended periods of time is associated with genotoxicity. The Specific Absorption Rate (SAR) values of mobile phones indicate that they release less radiofrequency radiation, which is discovered to be within a safer limit. This is the case because SAR values can be measured. The use of mobile phones for extended periods of time may also cause DNA damage in human cells. Methods: The purpose of this study is to analyse the impact that radiation from mobile phones have on fertility by analysing the quality of the sperm of people who use their phones often. Results: The research was carried out on a total of 150 people who were between the ages of 20 and 40 and divided into three groups (frequent mobile users, moderate mobile users and less mobile phone users). Prior to collecting samples from the subjects, permission was obtained from them. The researcher conducted individual interviews with each participant in the study in order to collect information for filling out a structured questionnaire. Analyses and comparisons were made between the three groups on the properties of the sperm, including their motility and shape. Conclusion: The findings of a number of research indicate that radiations released by mobile phones have an effect on male fertility by causing permanent alterations in the morphology of the semen. The current research demonstrates that there is a problem with the fertilising ability of sperm due to defects and changes in sperm morphology. According to the findings of this research, radiations released by mobile phones will have an effect on male fertility. The genotoxic impact may be brought to the attention of regular users of mobile phones and the required measures can be taken via the use of biosensors, which offer a warning signal or alarm when the radiations level exceeds the usual limit.

Low profile multi-polarization diversity UWB antenna for body centric communications

Abstract A low-profile multi-polarized MIMO ultra-wideband antenna suitable for body-centric communications is reported. MIMO configuration is achieved using the symmetric heptagonal monopole (SHM) antenna, a mirrored SHM antenna, an asymmetric ruby-shaped monopole (ARSM) antenna, and a mirrored ARSM antenna placed over the modified C-shaped ground plane (MCGP). The proposed antenna elements are designed to achieve resonance for the entire ultra-wideband frequency range. The SHM antenna is coupled with a co-planar waveguide to produce linear polarization. An ARSM antenna generates circular polarization utilizing an asymmetric geometry both in the radiator and a truncated ground plane. Both the SHM antenna and an ARSM antenna are aligned face-to-face over an MCGP plane and good isolation &gt;15 dB is realized between the antenna elements. The gain and total efficiency for linear polarized and the circularly polarized antennas are 3.05–4.8 dBi/48–66% and from 2.8 to 5 dBic/52 to 70.5%, respectively. The specific absorption rate values are evaluated to understand their suitability for WBAN communications.

A fully flexible, high gain saw-tooth-shaped boundary fractal wearable patch antenna for WBAN applications

AbstractA flexible and high gain saw-tooth-shaped boundary fractal wearable antenna is anticipated for WBAN applications. A square shape is converted to the saw-tooth-shaped boundary by sequentially rotating the square at an angle of 45° and overlaid on one another and repeated the same for three iterations. The geometry is built on a flexible jeans substrate, and the total size of the anticipated antenna is 0.583λ × 0.583λ × 0.02λ at 2.4 GHz. A prototype has been made to test its suitability for wearable applications' gain, bandwidth, and efficiency. The results revealed that the proposed antenna provides an impedance bandwidth of 4.2% and a peak gain of 5.76 dBi at the 2.45 GHz ISM band. The anticipated antenna is wrapped around foam cylinders of radii 70 and 50 mm to test the stability and deformability of its performance. The full ground plane isolates the antenna from the human body contributing to the lower SAR values. The simulated maximum achieved specific absorption rate (SAR) of 0.3025 and 1.16 W/kg for 10 and 1 g of average tissue for the input power of 100 mW, respectively, found within the standards as per FCC. The peak gain, compact size, and SAR permanence made the anticipated antenna a worthy candidate for wearable on/off body applications.

Low-profile Button Sensor Antenna Design for Wireless Medical Body Area Networks.

A button sensor antenna (BSA) for wireless medical body area networks (WMBAN) is presented, which works through the IEEE 802.11b/g/n standard. Due to strong interaction between the sensor antenna and the body, a new robust system is designed with a small footprint that can serve on- and off-body healthcare applications. The measured and simulated results are matched well. The design offers a wide range of omnidirectional radiation patterns in free space, with a reflection coefficient (S11) of -29.30 (-30.97) dB in the lower (upper) bands. S11 reaches up to -23.07 (-27.07) dB and -30.76 (-31.12) dB on the body chest and arm, respectively. The Specific Absorption Rate (SAR) values are below the regulatory limitations for both 1-gram (1.6 W/Kg) and 10-gram tissues (2.0 W/Kg). Experimental tests of the read range validate the results of a maximum coverage range of 40 meters. Clinical Relevance- WMBAN technology allows for continuous monitoring and analysis of patient health data to improve the quality of healthcare services.

Microstructural, optical, and magnetic properties and specific absorption rate of bismuth ferrite/SiO2 nanoparticles

In this study, the microstructural, optical, and magnetic properties and specific absorption rate (SAR) of bismuth ferrite/SiO2 nanoparticles were successfully investigated. The coprecipitation method was used to synthesize the nanoparticles. X-ray diffraction patterns showed the presence of sillenite-type Bi25FeO40 with a body-centered cubic structure. The crystallite size of Bi25FeO40 was 35.0 nm, which increased to 41.5 nm after SiO2 encapsulation. Transmission electron microscopy images confirmed that all samples were polycrystalline. The presence of Si–O–Si (siloxane) stretching at 1089 cm−1 in Fourier transform infrared spectra confirmed the encapsulation of SiO2. Magnetic measurements at room temperature indicated weak ferromagnetic properties of the samples. The coercivity of the bismuth ferrite nanoparticles was 78 Oe, which increased after SiO2 encapsulation. In contrast, their maximum magnetization, 0.54 emu g−1, reduced after SiO2 encapsulation. The determined bandgap energy of the bismuth ferrite nanoparticles was approximately 2.1 eV, which increased to 2.7 eV after SiO2 encapsulation. The effect of SiO2 encapsulation on the SAR of the samples was investigated using a calorimetric method. The SAR values of the bismuth ferrite nanoparticles were 49, 61, and 84 mW g−1 under alternating magnetic field (AMF) strengths of 150, 200, and 250 Oe, respectively, which decreased after SiO2 encapsulation. The maximum magnetization and the AMF strength influenced the SAR of the nanoparticles. The results showed that SiO2 has a significant effect in determining the microstructural, optical, and magnetic properties and SAR of the nanoparticles.

Thermal Effect Estimation of Smartphone Virtual Reality Headsets on Human Eye by Finite Element Method

Smartphones (SP) terminals are becoming the most popular media for virtual reality (VR) and augmented reality (AR) effects with their central processing unit (CPU) and video capabilities. Simple VR headsets with reasonable costs can host smartphones, and they can together be used for many different applications. But with the outbreak of Covid-19 pandemic, their usage has become essential for many people working from their homes. VR and AR capabilities provide a much richer experience for entertainment, gaming, and video conferencing. The increasing popularity of 3D virtual worlds add up to this usage. On the technology side, multi-radio connectivity is supported both on terminal and network side. A certain risk may arise when using SP VR headsets for such applications requiring a broadband Internet connectivity. SPs with multi-radio connectivity feature may elevate specific absorption rate (SAR) values in those cases. The smartphone used for VR and AR applications is positioned in front of the eyes; and there is very limited ventilation in VR/AR headsets. Authors’ model aims simulate these exposure scenarios in 4G and 5G mobile telecommunication frequencies by finite element method (FEM); and, possible thermal and non-thermal risks of related electromagnetic (EM) radiation on human eye according to the outputs of the model are discussed.