scholarly journals Effect of A Superstrate on On-Head Matched Antennas for Biomedical Applications

Electronics ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1099
Author(s):  
Md Rokunuzzaman Robel ◽  
Asif Ahmed ◽  
Akram Alomainy ◽  
Wayne S. T. Rowe
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Performance Improvement ◽  
Direct Contact ◽  
Biomedical Applications ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Conducting Layer ◽  
Electric And Magnetic Field ◽  
Biomedical Diagnosis

The effect of using a superstrate dielectric layer on an on-head matched antenna for biomedical diagnosis applications is investigated. Two on-head matched antennas are considered with different length meandered lines ensuring operation around 0.9 GHz frequency. The first antenna’s conductive radiating structure is in direct contact with the head phantom, whereas the second one utilises a 0.5 mm thick superstrate layer on top of the conducting layer as a buffer. The lateral dimensions of both antennas are held constant at 30 × 30 mm2. The electric and magnetic field distribution is analysed and the power penetration, 50 mm inside the head phantom, is derived from the electromagnetic field surrounding the antennas. Both homogeneous and inhomogeneous head phantoms are considered while evaluating the antennas in terms of their reflection coefficient, current distribution, electric field, magnetic field, specific absorption rate (SAR) and power penetration inside the head. The antennas are fabricated and measured utilizing an inhomogeneous phantom to validate the proposed performance improvement using a superstrate. It is shown that the superstrate antenna achieves a ~8 dB increase in power penetration inside the head phantom along with a 0.0731 W/kg decrease in SAR compared to the antenna without a superstrate.

scholarly journals A Physically-Motivated Quantisation of the Electromagnetic Field on Curved Spacetimes

Entropy ◽  
2019 ◽  
Vol 21 (9) ◽  
pp. 844
Author(s):  
Ben Maybee ◽  
Daniel Hodgson ◽  
Almut Beige ◽  
Robert Purdy
Keyword(s):  
Magnetic Field ◽  
Field Theory ◽  
Quantum Field Theory ◽  
Electromagnetic Field ◽  
Minkowski Space ◽  
Unruh Effect ◽  
Quantum Field ◽  
Rindler Space ◽  
Electric And Magnetic Field ◽  
Curved Spacetimes

Recently, Bennett et al. (Eur. J. Phys. 37:014001, 2016) presented a physically-motivated and explicitly gauge-independent scheme for the quantisation of the electromagnetic field in flat Minkowski space. In this paper we generalise this field quantisation scheme to curved spacetimes. Working within the standard assumptions of quantum field theory and only postulating the physicality of the photon, we derive the Hamiltonian, H ^ , and the electric and magnetic field observables, E ^ and B ^ , respectively, without having to invoke a specific gauge. As an example, we quantise the electromagnetic field in the spacetime of an accelerated Minkowski observer, Rindler space, and demonstrate consistency with other field quantisation schemes by reproducing the Unruh effect.

Short-wave electromagnetic field effects on adrenal glands functional status in the rats

10.12737/7594 ◽  
2015 ◽  
Vol 9 (1) ◽  
pp. 0-0
Author(s):  
Алабовский ◽  
V. Alabovskiy ◽  
Кудряшов ◽  
Yu. Kudryashov ◽  
Перов ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Functional Activity ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Adrenal Glands ◽  
Biological Effects ◽  
Male Rats ◽  
Field Exposure ◽  
Specific Absorption ◽  
Tem Cell

The article presents the investigation results of the electromagnetic field biological effects on adrenal glands functional activity in the rats. The electromagnetic field exposure levels were typical electromagnetic fields of portable radios (walkie-talkies). Experiments were carried out on laboratory male rats. Experimental groups were exposured in a transverse electromagnetic wave cell - TEM cell. Sham animal groups were in similar conditions, but without electromagnetic field exposure. The exposure of experimental animals was carried out in three series (12 rats for each group) for three levels of the electric field strength such as 15; 25 and 35 V/m. Gluco-corticoid and mineral-corticoids adrenal functions were assessed by determining the corticosterone and of Na+ and K+ levels in daily urinary excretion. The animal specific absorption rate evaluations were calculated by using the program SEMCAD X v.14 and experimentally in the TEM cell. The dependences of the excretion of corticosterone and electrolytes on the specific absorption rate and exposure time, which indicate that for small values of electromagnetic energy absorption is stimulation of the adrenal glands functional activity, alternating with depression by specific absorption rate increasing.

Research on Frequency Electromagnetic Field of Parallel Transmission Line

2014 ◽  
Vol 986-987 ◽  
pp. 1992-1995
Author(s):  
Hong Ying Cao ◽  
Bo Tang ◽  
You Xian Peng ◽  
Yu Li ◽  
Bin Chen
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Transmission Line ◽  
Transmission Lines ◽  
The State ◽  
National Standards ◽  
Power Lines ◽  
Three Gorges ◽  
Parallel Transmission ◽  
Electric And Magnetic Field

At present the study mainly for frequency electromagnetic field which is based on a single transmission line meanwhile the value must be in line with the requirements of the workers in the country frequency electromagnetic field. However, for parallel transmission line the maximum of frequency electromagnetic field is still to meet the provisions of the state, therefore in this paper studied the parallel transmission lines. Taking the multiple parallel power lines of China Three Gorges University as an example, the values of electric and magnetic field are calculated and the electromagnetic field is measured based on National standards. Then, compare the measured value with theoretical value, verified the correctness of the superposition algorithm.

scholarly journals Dynamics of superparamagnetic nanoparticle in viscous liquid in rotating magnetic field

2019 ◽  
Author(s):  
Nikolai A Usov ◽  
Ruslan A Rytov ◽  
Vasiliy A Bautin
Keyword(s):  
Magnetic Field ◽  
Viscous Liquid ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Stochastic Equation ◽  
Magnetization Vector ◽  
Superparamagnetic Nanoparticles ◽  
Rotating Magnetic Field ◽  
Field Frequency ◽  
Specific Absorption

The dynamics of magnetic nanoparticle in a viscous liquid in rotating magnetic field has been studied by means of numerical simulation and analytical calculations. In the magneto- dynamics approximation three different modes of motion of the unit magnetization vector and particle director are distinguished depending on the rotating magnetic field frequency and amplitude. The specific absorption rate of a dilute assembly of superparamagnetic nanoparticles in rotating magnetic field is calculated by solving the Landau – Lifshitz stochastic equation for unit magnetization vector and stochastic equation for particle director. At elevated frequencies an optimal range of particle diameters is found where the specific absorption rate of an assembly in rotating magnetic field has a maximum. It is shown that for magnetic hyperthermia in rotating magnetic field it is preferable to use rotating magnetic fields of moderate amplitude, H 0 = 100 Oe, in the frequency range 400-600 kHz.

Elongated magnetic nanoparticles with high-aspect ratio: a nuclear relaxation and specific absorption rate investigation

2019 ◽  
Vol 21 (34) ◽  
pp. 18741-18752
Author(s):  
Matteo Avolio ◽  
Helena Gavilán ◽  
Eva Mazario ◽  
Francesca Brero ◽  
Paolo Arosio ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
Aspect Ratio ◽  
Physical Properties ◽  
High Aspect Ratio ◽  
Biomedical Applications ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Nuclear Relaxation ◽  
Specific Absorption ◽  
Elongated Nanoparticles

High aspect-ratio elongated nanoparticles with suitable porosity present partially controlled chemico-physical properties to obtain good heating/contrast efficiency for biomedical applications.

scholarly journals Quantitative Analysis of the Specific Absorption Rate Dependence on the Magnetic Field Strength in ZnxFe3−xO4 Nanoparticles

2020 ◽  
Vol 21 (20) ◽  
pp. 7775
Author(s):  
Mohamed Alae Ait Kerroum ◽  
Cristian Iacovita ◽  
Walid Baaziz ◽  
Dris Ihiawakrim ◽  
Guillaume Rogez ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Large Diameter ◽  
Precipitation Method ◽  
Magnetization Relaxation ◽  
Specific Absorption ◽  
The Magnetic Field ◽  
Néel Relaxation

Superparamagnetic ZnxFe3−xO4 magnetic nanoparticles (0 ≤ x < 0.5) with spherical shapes of 16 nm average diameter and different zinc doping level have been successfully synthesized by co-precipitation method. The homogeneous zinc substitution of iron cations into the magnetite crystalline structure has led to an increase in the saturation magnetization of nanoparticles up to 120 Am2/kg for x ~ 0.3. The specific absorption rate (SAR) values increased considerably when x is varied between 0 and 0.3 and then decreased for x ~ 0.5. The SAR values are reduced upon the immobilization of the nanoparticles in a solid matrix being significantly increased by a pre-alignment step in a uniform static magnetic field before immobilization. The SAR values displayed a quadratic dependence on the alternating magnetic field amplitude (H) up to 35 kA/m. Above this value, a clear saturation effect of SAR was observed that was successfully described qualitatively and quantitatively by considering the non-linear field’s effects and the magnetic field dependence of both Brown and Neel relaxation times. The Neel relaxation time depends more steeply on H as compared with the Brown relaxation time, and the magnetization relaxation might be dominated by the Neel mechanism, even for nanoparticles with large diameter.

scholarly journals Dynamics of superparamagnetic nanoparticles in viscous liquids in rotating magnetic fields

2019 ◽  
Vol 10 ◽  
pp. 2294-2303
Author(s):  
Nikolai A Usov ◽  
Ruslan A Rytov ◽  
Vasiliy A Bautin
Keyword(s):  
Magnetic Field ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Stochastic Equation ◽  
Magnetization Vector ◽  
Optimal Choice ◽  
Superparamagnetic Nanoparticles ◽  
Rotating Magnetic Field ◽  
Rotating Magnetic Fields ◽  
Specific Absorption

The dynamics of magnetic nanoparticles in a viscous liquid in a rotating magnetic field has been studied by means of numerical simulations and analytical calculations. In the magneto-dynamics approximation three different modes of motion of the unit magnetization vector and particle director are distinguished depending on frequency and amplitude of the rotating magnetic field. The specific absorption rate of a dilute assembly of superparamagnetic nanoparticles in rotating magnetic field is calculated by solving the Landau–Lifshitz stochastic equation for the unit magnetization vector and the stochastic equation for the particle director. At elevated frequencies an optimal range of particle diameters is found where the specific absorption rate of an assembly in a rotating magnetic field has a maximum. It is shown that with an optimal choice of the particle sizes sufficiently large SAR values of the order of 400–500 W/g can be obtained in a rotating magnetic field with a frequency f = 400 kHz and a moderate magnetic field amplitude H 0 = 100 Oe.

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