Frequency Electromagnetic Fields Research Articles

Free electron emission in vacuum assisted by photonic time crystals

The Cerenkov radiation and Smith–Purcell (SP) effect state that free electron emission occurs exclusively in dielectrics when the velocity of the particles exceeds the speed of light in the medium or in the vicinity of periodic gratings close to each other within a vacuum. We demonstrate that free electrons in a vacuum can also emit highly directional monochromatic waves when they are in close proximity to a medium that is periodically modulated temporally, suggesting the existence of the temporal SP effect. The momentum band gaps of time-varying media, such as photonic time crystals (PTCs), create new pathways for the injection of external energy, allowing the frequency, intensity, and spatial distribution of electromagnetic fields to be controlled. Moreover, the PTC substrate enables the conversion of localized evanescent fields into amplified, highly directional propagating plane waves that are only sensitive to the velocity of particles and the modulation frequency, which allows us to observe and utilize Cerenkov-like radiation in free space. Our work presents significant opportunities for the utilization of time-varying structures in various fields, including particle identification, ultraweak signal detection, and improved radiation source design.

Influence of Magnetic Polarization on Diagrams of Inductive and Electromagnetic Logs

Abstract ––We present the results of the study of the effect of induced magnetic polarization of clay beds under the influence of an external harmonic electromagnetic field (frequencies 70 and 875 kHz). A two-stage numerical modeling procedure is proposed. At the first stage we determine the effective relative magnetic permeability of a synthetic sample with inclusions of clay particles. In this case a 3D heterogeneous mesh sample is generated. Then we numerically model a spatial distribution of an electric field. The electromotive force (EMF) induced in the measuring coil is calculated from this distribution. Relative magnetic permeability is determined by comparison with EMF of homogeneous samples with different values of magnetic permeability. It has been found that during the electric field excitation by an alternating current coil, the effect of induced magnetic polarization appears in the sample with clay particles. Its manifestation is that the effective magnetic permeability becomes complex. At the second stage we calculate the EMF diagram of the three-coil logging probe in the macro-model ‘clay cap – reservoir’. Magnetic permeability of the clay cap is given by a complex value. In the generated logs, extremes appear in the vicinity of the bottom of the clay cap; they do not correspond to the distribution of electrical conductivity and magnetic permeability in the given model. They can be incorrectly interpreted when analyzing real logs into individual formations. Numerical modeling at all stages is performed by the Vector Finite Element Method on a consistent adaptive tetrahedral partition and the first-order Webb vector basis.

Effects of Electromagnetic Field Frequency on the Behavior and Mortalities of Living Organisms

Effects of Electromagnetic Field Frequency on the Behavior and Mortalities of Living Organisms

Theory design and dynamic testing of Magnetic Tunnel Junction (MTJ) spin microwave detection chip

The magnetic tunnel junction (MTJ) chip has recently been verified in numerous studies as a microwave detection or microwave radiation unit. In this paper, a theoretical model for a coplanar chip incorporating an MTJ for microwave detection is established, and it is shown how the electromagnetic characteristics of the MTJ varied with the frequency, amplitude, and phase of the microwave electromagnetic field in simulations and experiments. Based on several studies of our research, meaningful conclusions are provided to direct the processing and dynamic detection of microwave electromagnetic fields in MTJ chips. Initially, the micrometer-sized MTJ chip was fabricated by using a lithography process directly on the signal line of coplanar waveguide. It was found that the detection chip voltage (μV level) increased linearly with microwave power from 3 dBm to 20 dBm. The frequency of the microwave field and the static magnetic field along the easy axis cause the probe voltage of the chip to change in a wave-peak–valley curve, and the amplitude of the probe signal slightly increases with frequency. Additionally, theoretical and experimental results indicate that this is a combined result of spin magneto-resistance and ferromagnetic resonance absorption. In the experiments, two microwave beams were applied in opposite, and the resulting detection voltage clearly represented an interference effect. The test signal’s phase also changed according to a trigonometric function, with a maximum value varying between a few and several hundreds of μV. The aforementioned findings demonstrate that MTJs can theoretically and practically be utilized as spectrometers to detect microwave electromagnetic fields.

Glioblastoma behavior study under different frequency electromagnetic field

The tumor-treating fields (TTFields) technology has revolutionized the management of recurrent and newly diagnosed glioblastoma (GBM) cases. To ameliorate this treatment modality for GBM and other oncological conditions, it is necessary to understand the biophysical principles of TTFields better. In this study, we further analyzed the mechanism of the electromagnetic exposure with varying frequencies and electric field strengths on cells in mitosis, specifically in telophase. In reference to previous studies, an intuitive finite element model of the mitotic cell was built for electromagnetic simulations, predicting a local increase in the cleavage furrow region, which may help explain TTFields' anti-proliferative effects. Cell experiments confirmed that the reduction in proliferation and migration of glioma cell by TTFields was in a frequency- and field-strength-dependent manner. This work provides unique insights into the selection of frequencies in the anti-proliferative effect of TTFields on tumors, which could improve the application of TTFields.

Quantum Metrology Using Time-Frequency as Quantum Continuous Variables: Resources, Sub-Shot-Noise Precision and Phase Space Representation.

We study the role of the electromagnetic field's frequency on the precision limits of time measurements from a quantum perspective, using single photons as a paradigmatic system. We demonstrate that a quantum enhancement of precision is possible only when combining both intensity and spectral resources and, in particular, that spectral correlations enable a quadratic scaling of precision with the number of probes. We identify the general mathematical structure of nonphysical states that achieve the Heisenberg limit and show how a finite spectral variance may cause a quantum-to-classical-like transition in precision scaling for pure states similar to the one observed for noisy systems. Finally, we provide a clear and consistent geometrical time-frequency phase space interpretation of our results, identifying what should be considered as spectral classical resources.

Nanozyme-Based Robotics Approach for Targeting Fungal Infection.

Fungal pathogens have been designated by the World Health Organization as microbial threats of the highest priority for global health. It remains a major challenge to improve antifungal efficacy at the site of infection while avoiding off-target effects, fungal spreading, and drug tolerance. Here, a nanozyme-based microrobotic platform is developed that directs localized catalysis to the infection site with microscale precision to achieve targeted and rapid fungal killing. Using electromagnetic field frequency modulation and fine-scale spatiotemporal control, structured iron oxide nanozyme assemblies are formed that display tunable dynamic shape transformation and catalysis activation. The catalytic activity varies depending on the motion, velocity, and shape providing controllable reactive oxygen species (ROS) generation. Unexpectedly, nanozyme assemblies bind avidly to fungal (Candida albicans) surfaces to enable concentrated accumulation and targeted ROS-mediated killing in situ. By exploiting these tunable properties and selective binding to fungi, localized antifungal activity is achieved using in vivo-like cell spheroid and animal tissue infection models. Structured nanozyme assemblies are directed to Candida-infected sites using programmable algorithms to perform precisely guided spatial targeting and on-site catalysis resulting in fungal eradication within 10 min. This nanozyme-based microrobotics approach provides a uniquely effective and targeted therapeutic modality for pathogen elimination at the infection site.

Dosimetric assessment in the brain for downlink EMF exposure in Korean mobile communication networks

Because the position and direction of the human body is not fixed in an actual environment, the incidence direction of the electromagnetic field (EMF) from mobile communication base stations, WiFi access points, broadcasting towers, and other far-field sources is arbitrary. To analyze the overall health effects of radio frequency EMF exposure, the dosimetric assessment for such environmental exposures created from an unspecified number of sources in daily life, along with exposures from specific EMF sources, must be quantified. This study is aimed at numerically evaluating the time-averaged specific absorption rate (SAR) of the human brain for environmental EMF exposure in the frequency range of 50–5800 MHz. Whole-body exposure to EMFs that are evenly incident spatially is considered. By comparing the results of several incidence directions and the number of polarizations, an optimal calculation condition has been derived. Finally, based on the results measured in Seoul at the end of 2021, the SAR and daily specific energy absorption (SA) in the brains of both a child and an adult for downlink exposures from 3G to 5G base stations are reported. Comparison results of the daily brain SA for exposure to DL EMF in all 3G to 5G mobile networks and exposure to a 10-min voice call (uplink EMF) using a mobile phone connected to a 4G network show that the SA from the downlinks is much higher than that from the uplinks.

Extremely Low Frequency-Electromagnetic Fields (ELF-EMF) Can Decrease Spermatocyte Count and Motility and Change Testicular Tissue

Substantial evidence indicates that exposure to extremely low frequency-electromagnetic fields (ELF-EMFs) affects male reproductive system. The goal of this study was to evaluate the effects of long-term irradiation with ELF-EMF on sperm quality and quantity and testicular structure. In this case-control study, sixty male Sprague-Dawley rats were randomly divided into six groups. Experimental groups were exposed to ELF-EMF (50 Hz EMF, 100 µT) for either 1 h/day for 52 days (Group 1), 4 h/day for 52 days (Group 3), 1 h/day for 5 days (Group 5), 4 h/day for 52 days (Group 7). Groups 2, 4, 6 and 8 were only sham exposed at durations equal to Groups 1, 3, 5 and 7, respectively. Both count and motility of sperms were significantly decreased in animals exposed to ELF-EMF (1 h/day for 52 days, 4 h/day for 52 day, and 4 h/day for 5 days) compared to the sham-exposed groups (P<0.05). Serum testosterone levels showed a significant decrease in the animals exposed to ELF-EMF (4 h/day for 5 days) compared to the control groups (P<0.05). A significant decrease was observed in the volume of the seminiferous tubules, seminiferous tubules epithelium and interstitial tissue in the animals exposed to ELF-EMF for 4 h/day for 5 days. Tubules length was also reduced by 18% in animals exposed to ELF-EMF (4 h/day for 5 days). Our results show that ELF-EMF can reduce spermatocyte count and motility and is able to induce structural changes in testicular tissue.

Electromagnetic Field Effect on Bone Marrow Stem Cells Differentiation and Nucleoli AgNOR

Purpose: Numerous studies have described the effect of Electromagnetic Fields (EMFs) in the promotion of Bone Marrow Stem Cell (BMSC) differentiation. We aimed to investigate the influence of frequency (10 and 100 Hz) and different pulse shapes (sine, rectangular, and triangular) of EMF on rats' BMSCs.&#x0D; Materials and Methods: The BMSCs in 6 groups were exposed to EMF for 1 h/ 7 days. The BMSCs viability was estimated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test. The cresyl violet labeled the Nissl bodies, and the silver nitrate staining was done to evaluate the BMSCs nucleoli AgNORs.&#x0D; Results: The MTT test verified that EMF and pulse shape did not affect cell viability. In Nissl bodies staining most of the large neurons were related to the rectangular 10 Hz EMF group. The majority of the differentiated BMSCs were astrocytes, microglia, and oligodendrocyte in the triangular 100 Hz EMF group. Although the silver nitrate staining confirmed the effect of 10 Hz EMF, pulse shape alteration did not affect AgNOR parameters. In conclusion, we presented a low-magnetic flux density EMF (400 µT) to assess the responses of BMSCs nuclei.&#x0D; Conclusion: The findings showed that BMSCs differentiation was frequency-dependent. Further investigations are recommended for recognizing the function of EMF on BMSCs.

Influence of the frequency of external electromagnetic field on the structure of 09G2S steel welded joints

Influence of the frequency of external electromagnetic field on the structure of 09G2S steel welded joints

ВЛИЯНИЕ ДИЭЛЕКТРИЧЕСКИХ РЕЛАКСАЦИЙ ПОЧВЕННОЙ ВОДЫ НА ТЕМПЕРАТУРНУЮ ЗАВИСИМОСТЬ ДИЭЛЕКТРИЧЕСКОЙ ПРОНИЦАЕМОСТИ ПОЧВЫ

The influence of the dielectric constant spectra of bound and unbound water in mineral soil on the temperature dependences of the dielectric constant of mineral soil in the electromagnetic field frequency range from 50 MHz to 15 GHz was studied. The reasons for the appearance of the crossover frequency of the dielectric constant of mineral soil, obtained at different temperatures, but for a sample of the same moisture, were studied. It was proved that the appearance of crossover points in the frequency range up to 1.5 GHz is related to the Maxwell-Wagner effect in bound water. The dependences of the value of the crossover frequency of the dielectric constant of mineral soil on temperature and the volume content of bound and unbound water were studied.

Effects of frequencies ranging from 100 to 400 Hz on electromagnetic field assisted freezing of grass carp (Ctenopharyngodon idellus)

This study aimed to understand the effects of electromagnetic field (EMF) frequencies on the freezing of grass carp tissue. Frequencies ranging from 100 to 400 Hz with a fixed strength of 12 mT were applied during freezing. Results showed that the initial freezing point was significantly increased (p < 0.05) for treatment between 200 and 400 Hz compared with control, but the phase change duration was not affected. Reductions in ice areas and crystal sizes were also observed. The highest initial freezing point of −1.44 °C was obtained at 300 Hz with a 45% reduction in crystal size (19.29 μm). There were also no subsequent changes in the drip, texture, colour and pH values. These results indicated that the oscillation among ions due to applying EMF favoured ice crystallization, and frequencies between 200 and 400 Hz were suitable for improving the freezing process assisted by the electromagnetic field.

Hygienic assessment of electromagnetic fields generated by promising models of power plants

Introduction. The analyses of staff occupationally connected with maintenance and operation of plants included in the Federal Project “Development of technologies for Controlled Thermonuclear Fusion (CTF) and innovative plasma technologies” electromagnetic safety problems required full-scale measurements of the electromagnetic fields (EMF) and hygienic assessment in personnel workplaces. Materials and methods. Measurements of EMF frequency and intensity-time parameters and preliminary hygienic assessment in workplaces of Tokamaks MEFIST-0, T-11M, TUMAN-3M, FT-2, magnetic trap MK-200M were carried out. Results. The studies showed very high levels of pulsed magnetic fields (MF) (up to 433 mT), despite of official regulatory values absence, according to magnetic component effects mechanisms can be assessed as human health risk factor. Radio frequency EMF levels, despite the short-term exposure, can have the adverse effect on human health, because in all points of possible employees’ location there were exceeding the maximum permissible values (up to 170 fold). 1 Hz-1 kHz frequency range EMF electric and magnetic components amplitude-frequency characteristics peaks may be risk factor for human health too (despite the lack of this frequency range hygienic standards in Russia). Limitations. The limitations of the study are determined by the lack of generated by new CTF samples EMF frequency and intensity-time parameters objective data. Conclusion. EMF assessment in examined CTF staff work places pilot study showed that pulsed MF, radio frequency EMF, 1 Hz-1 kHz frequency range EMF both components levels reach very high values and, despite the absence of officially valid regulatory values, according to factor action mechanisms, can be risk factor for personnel health.

КОНТРОЛЬ ПАРАМЕТРОВ ТЕМПЕРАТУРНОГО РАСПРЕДЕЛЕНИЯ В ПРЕДПЛЕЧЬЕ ЧЕЛОВЕКА ПРИ ПРОЦЕДУРЕ УВЧ-ГИПЕРТЕРМИИ МЕТОДАМИ ПАССИВНОЙ АКУСТИЧЕСКОЙ ТЕРМОМЕТРИИ И ИНФРАКРАСНОЙ ТЕРМОГРАФИИ

In this work we performed UHF heating with an electromagnetic field of frequency 40.68 MHz and power of 30 W on human forearms and phantoms made of plastisol with simulated blood flow at physiotherapeutic doses of 10, 15 and 20 minutes. Thermal acoustic radiation of heated objects measured with a multichannel acoustothermograph with a bandwidth of 1.6-2.5 MHz, an integration time of 10 C, and a threshold sensitivity of 0.2 K. Additionally, the surface temperature of the forearm measured by infrared thermometry and the internal temperature of the phantom by an electronic thermometer. We obtained data about temperature distribution patterns in the human forearm and in the plastisol phantom. Blood flow in the phantoms was simulated by copper, aluminum and polyvinyl chloride tubes, through which water from a thermostat was passed. Comparison of cooling rates of different types of phantoms showed that the thermal properties of the phantom with aluminum tubes were the closest to the soft tissues of the human forearm. The data of objective control do not agree with the subjective sensations of the subjects, but agree well with each other, which confirms the necessity and shows the possibility of objective assessment of temperature distribution parameters in the soft tissues of the human body during hyperthermia during UHF-physiotherapy.

Frequency dependencies of the characteristics of an inductively coupled radiofrequency discharge at reduced pressure

The dependence of parameters of an inductively coupled radiofrequency plasma on the electromagnetic field frequency in range 0.25–40 MHz at reduced pressure (113 Pa) was studied. The study was carried out in a 2D axisymmetric time-dependent setting, implemented in the Comsol multiphysics software package using the Navier–Stokes equations, continuity equation for electron density, electron energy density equation, ion density equation, metastable atom density equation, heat transfer equation, Maxwell and Poisson equations for electromagnetic fields. The distributions of the plasma parameters at the output of the discharge tube in dependence on electromagnetic field frequency were obtained. It was found that the dependences of the electron density, electron temperature, and gas temperature on the field frequency are non-linear. The maximum value of these quantities were achieved at different frequencies depending on the discharge power. A mechanism relating the frequency and power to the shift in the positions of the maxima of these plasma parameters is proposed.

Formation of the quality of wheat grain by extremely low frequency electromagnetic field treatment

The object of the study is the treatment of wheat grain with an electromagnetic field (EMF) of extremely low frequencies (ELF), the subjects of the study are the quality indicators of wheat seed grain of the Shestopalivka variety 2019 and 2020 crops grown in the Odesa region. (Ukraine). Problematic issues in the treatment of wheat grain with ELF EMF are the rationale for the duration of treatment of grain and the frequencies of EMF that improves the quality of seeds. The studies used methods of laboratory determination of seed quality indicators, calculation of statistical characteristics of the length of sprouts, and graphical methods for interpreting the results of studies. The studies substantiated the modes of treatment wheat grain with ELF EMF, which improves the quality of seeds and reduces the energy intensity of treatment. The effect of the duration of grain treatment and the frequency of EMF on the germination and characteristics of the length of seed shoots was studied. It has been established that, compared with untreated grain, the treatment of grain with an EMF with a frequency of 30 Hz, a magnetic induction of 10 mT for 6 minutes increases grain germination by 2–3 %, gives longer and 1.44–1.53 times more uniformly sprouted sprouts. Treatment within 60 min. reduces up to 9 % the germination of grain, the size of the shoots, increases their unevenness in length. The effect of seed germination activation by EMF treatment increases after 19 days of storage. Treatment of wheat grain in 2019 with ELF EMF at a frequency of 15–17 Hz with a magnetic induction of 10 mT for 6 min. changes germination within ±3 % control. The germination of the treated grain of wheat in 2020 of the crop decreases relative to the control to 13 % (with the exception of the frequency of 16.5 Hz, at which it did not change). Thus, the treatment of wheat grain with EMF makes it possible to influence the quality of seed grain. The results obtained encourage further research with a wider range of regime parameters and areas of wheat cultivation.

Ca2+ATPase enzyme activities and lipid and protein oxidations of grass carp (Ctenopharyngodon idellus) stored at 4 °C for 30 min under electromagnetic fields

This work studied the effects of electromagnetic fields (EMF) with frequencies between 100 and 400 Hz and a fixed strength of 12 mT on cold storage of grass carp at 4 °C for 30 min, and Ca2+ATPase enzyme activities, and lipid and protein oxidations in samples were measured to assess changes in intracellular Ca2+ concentration and oxidative stability. Results showed higher Ca2+ATPase activities in samples treated with EMF frequencies. Significant (p < 0.05) decreases occurred in protein oxidation for samples treated between 100 and 300 Hz, but an increase was observed for treatment with 400 Hz. However, the lipid oxidation increased for samples treated up to 200 Hz and decreased with further increase in frequency to 300 and 400 Hz. Nuclear magnetic resonance analysis showed that exposure to different frequencies of EMF could reduce the association of water molecules with protein for both bound and immobilized water. Overall, treatments of EMF between 100 and 400 Hz could improve grass carp quality during cold storage.

Frequency changes during the propagation of a light beam

The energy and therefore the frequency of electromagnetic fields are quantities which are generally considered to be conserved in free space propagation. However, we observe here a frequency varying optical wave in free space propagation. The light comes from an Arago spot. Its frequency changes due to the rotational Doppler effect. More precisely, the light diffracted by a two-dimensional asymmetric object carries orbital angular momentum that varies with distance. As the object rotates, the frequency of the diffracted light experiences different rotational Doppler shifts along propagation. It varies in a discrete quantized way as it propagates. It can be adjusted, without violation of the conservation of energy. Since this phenomenon is deeply rooted in the diffraction process, it sheds some new light on this still open issue.

On the effect of millimeter waves on DNA and RNA of viruses

Based on the differences between RNA and DNA, formulas for the natural frequency of torsional vibrations of single and double RNAs are obtained. It is shown that, despite the fact that millimeter waves are delayed by the skin of the human body, there are conditions under which they can freely penetrate through the human body. It is shown that centimeter waves, whose frequencies are multiples of the natural frequencies of torsional vibrations of the spirals of short DNA or RNA viruses, can cause subharmonic resonance in the spirals of RNA and DNA, which leads to the destruction of these molecules. Centimeter waves of non-thermal power flux density freely pass through the human body, which makes it possible to use them in vivo. A table has been compiled with the physical characteristics of DNA and RNA of the most dangerous viruses, indicating the frequencies of the external electromagnetic field that cause resonance in the DNA and RNA helices, which leads to the denaturation of molecules. In a series of experiments, it was shown that irradiation with microwaves with a resonant frequency of 180,402 GHz on samples with COVID-19 for 20 seconds. It has a disinfecting effect.