The Recommendation 1999/529/EU and the Directive 2013/35/EU suggest limits for both general publi... more The Recommendation 1999/529/EU and the Directive 2013/35/EU suggest limits for both general public and occupational exposures to extremely low-frequency magnetic fields, but without special limits for pregnant women. This study aimed to assess the compliance of pregnant women to the current regulations, when exposed to uniform MF at 50 Hz (100 μT for EU Recommendation and 1 and 6 mT for EU Directive). For general public, exposure of pregnant women and fetus always resulted in compliance with EU Recommendation. For occupational exposures, (1) Electric fields in pregnant women were in compliance with the Directive, with exposure variations due to fetal posture of <10 %, (2) electric fields in fetuses are lower than the occupational limits, with exposure variations due to fetal posture of >40 % in head tissues, (3) Electric fields in fetal CNS tissues of head are above the ICNIRP 2010 limits for general public at 1 mT (in 7 and 9 months gestational age) and at 6 mT (in all gestat...
2011 International Conference on Electromagnetics in Advanced Applications
This paper presents preliminary evaluation of the hybrid parallelization of the Finite-Difference... more This paper presents preliminary evaluation of the hybrid parallelization of the Finite-Difference Time-Domain (FDTD) method based on Open Computing Language (OpenCL) and the Message Passing Interface (MPI). Due to the portability of OpenCL, developed code targets not only distributed shared memory computer clusters based on multi-core central processing units (CPUs), but also clusters accelerated by graphics processing units (GPUs). The computational domain is decomposed along the slowest direction, and electromagnetic field boundary data is shared between neighboring subdomains using either OpenCL or MPI communication. The communication overhead between GPUs is proportional to the area of the boundary and represents the rate-limiting step of the method. This paper subsequently shows results of numerical tests aimed at evaluation of the hybrid OpenCL-MPI FDTD solver in electromagnetic simulations.
1999 International Symposium on Electromagnetic Compatibility (IEEE Cat. No.99EX147)
The necessity of near-field evaluation in wireless product development will strongly grow in the ... more The necessity of near-field evaluation in wireless product development will strongly grow in the coming years, since far-field evaluations provide insufficient information for analyzing and optimizing the performance of transmitters operating in complex environments. The objective of this paper is to review the latest progress in near-field measurement technology and to discuss future needs.
2013 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium)
ABSTRACT form only given. While contact-less power charging is becoming a popular feature in mode... more ABSTRACT form only given. While contact-less power charging is becoming a popular feature in modern electronic devices, the exposure to a nearby user from a wireless power transfer (WPT) system should be assessed prior to the commercial availability of such systems. In this study, a 4-link 100 kHz magnetically resonant low power wireless charging system is investigated with respect to the exposure of a user hand. Numerical dosimetry techniques are employed to compute the peak induced spatially averaged electric field (E-field) and specific absorption rate (SAR) in a high-resolution anatomically realistic hand model (based on an adult male hand). The computed peak values are analyzed with respect to the exposure limits recommended by the ICNIRP and IEEE exposure guidelines and standards (i.e., ICNIRP-2010, IEEE C95.6-2002 and IEEE C95.1-2005) to determine the compliance of the investigated WPT system and to derive the critical system parameters which could be adjusted to improve the design of a WPT system. A generic coil analysis is conducted by modelling a single circular coil with diameter in the range of 40 to 240 mm. An anatomical hand model, discretized with a uniform 1 mm grid resolution, is placed 1 mm above the coil with the center of the palm facing the center of the coil. The peak spatially averaged E-field (volume averaged for ICNIRP and line averaged for IEEE) values are plotted with the peak SAR (averaged over 1 gram or 10 gram) values to derive the transition frequency, above which, the peak spatial SAR becomes more dominant than the peak induced E-field for an exposure compliance assessment. This transition frequency can be regarded as the optimum operating frequency which leads to the highest output power of a WPT system with respect to the relevant exposure limits. Subsequently, the 4-link 100 kHz WPT system is modelled to facilitate the exposure analysis of an actual wireless charging system. This study provides the frequency-dependent user hand exp- sure characteristics of a generic circular coil and the exposure analysis of a practical wireless charging system. The computational results indicate that the optimum operating frequency of a WPT system with coil dimensions in the range of 40 mm to 240 mm diameter is approximately 1 MHz based on the peak 2×2×2 mm3 volume averaged E-field and 10 gram averaged SAR values. The investigated 4-link 100 kHz WPT system is found to be compliant with the ICNIRP and IEEE exposure limits while operating with a 5W output power.
Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology, 2017
Results from recent studies suggest that extremely low frequency magnetic fields (ELF-MF) interfe... more Results from recent studies suggest that extremely low frequency magnetic fields (ELF-MF) interfere with intracellular signaling pathways related to proliferative control. The mitogen-activated protein kinases (MAPKs), central signaling components that regulate essentially all stimulated cellular processes, include the extracellular signal-regulated kinases 1/2 (ERK1/2) that are extremely sensitive to extracellular cues. Anti-phospho-ERK antibodies serve as a readout for ERK1/2 activation and are able to detect minute changes in ERK stimulation. The objective of this study was to explore whether activation of ERK1/2 and other signaling cascades can be used as a readout for responses of a variety of cell types, both transformed and non-transformed, to ELF-MF. We applied ELF-MF at various field strengths and time periods to eight different cell types with an exposure system housed in a tissue culture incubator and followed the phosphorylation of MAPKs and Akt by western blotting. We f...
Extreme broadband wireless devices operating above 10 GHz may transmit data in bursts of a few mi... more Extreme broadband wireless devices operating above 10 GHz may transmit data in bursts of a few milliseconds to seconds. Even though the time- and area-averaged power density values remain within the acceptable safety limits for continuous exposure, these bursts may lead to short temperature spikes in the skin of exposed people. In this paper, a novel analytical approach to pulsed heating is developed and applied to assess the peak-to-average temperature ratio as a function of the pulse fraction α (relative to the averaging time [INCREMENT]T; it corresponds to the inverse of the peak-to-average ratio). This has been analyzed for two different perfusion-related thermal time constants (τ1 = 100 s and 500 s) corresponding to plane-wave and localized exposures. To allow for peak temperatures that considerably exceed the 1 K increase, the CEM43 tissue damage model, with an experimental-data-based damage threshold for human skin of 600 min, is used to allow large temperature oscillations t...
Radiofrequency radiation (RFR) causes heating, which can lead to detrimental biological effects. ... more Radiofrequency radiation (RFR) causes heating, which can lead to detrimental biological effects. To characterize the effects of RFR exposure on body temperature in relation to animal size and pregnancy, a series of short-term toxicity studies was conducted in a unique RFR exposure system. Young and old B6C3F1 mice and young, old, and pregnant Harlan Sprague-Dawley rats were exposed to Global System for Mobile Communication (GSM) or Code Division Multiple Access (CDMA) RFR (rats = 900 MHz, mice = 1,900 MHz) at specific absorption rates (SARs) up to 12 W/kg for approximately 9 h a day for 5 days. In general, fewer and less severe increases in body temperature were observed in young than in older rats. SAR-dependent increases in subcutaneous body temperatures were observed at exposures ≥6 W/kg in both modulations. Exposures of ≥10 W/kg GSM or CDMA RFR induced excessive increases in body temperature, leading to mortality. There was also a significant increase in the number of resorptio...
We report a noninvasive strategy for electrically stimulating neurons at depth. By delivering to ... more We report a noninvasive strategy for electrically stimulating neurons at depth. By delivering to the brain multiple electric fields at frequencies too high to recruit neural firing, but which differ by a frequency within the dynamic range of neural firing, we can electrically stimulate neurons throughout a region where interference between the multiple fields results in a prominent electric field envelope modulated at the difference frequency. We validated this temporal interference (TI) concept via modeling and physics experiments, and verified that neurons in the living mouse brain could follow the electric field envelope. We demonstrate the utility of TI stimulation by stimulating neurons in the hippocampus of living mice without recruiting neurons of the overlying cortex. Finally, we show that by altering the currents delivered to a set of immobile electrodes, we can steerably evoke different motor patterns in living mice.
Extremely-low-frequency magnetic fields (ELF-MF) have been classified as "possibly carcinoge... more Extremely-low-frequency magnetic fields (ELF-MF) have been classified as "possibly carcinogenic" to humans on the grounds of an epidemiological association of ELF-MF exposure with an increased risk of childhood leukaemia. Yet, underlying mechanisms have remained obscure. Genome instability seems an unlikely reason as the energy transmitted by ELF-MF is too low to damage DNA and induce cancer-promoting mutations. ELF-MF, however, may perturb the epigenetic code of genomes, which is well-known to be sensitive to environmental conditions and generally deranged in cancers, including leukaemia. We examined the potential of ELF-MF to influence key epigenetic modifications in leukaemic Jurkat cells and in human CD34+ haematopoietic stem cells undergoing in vitro differentiation into the neutrophilic lineage. During granulopoiesis, sensitive genome-wide profiling of multiple replicate experiments did not reveal any statistically significant, ELF-MF-dependent alterations in the pat...
Previous provocation experiments with persons reporting electromagnetic hypersensitivity (EHS) ha... more Previous provocation experiments with persons reporting electromagnetic hypersensitivity (EHS) have been criticised because EHS persons were obliged to travel to study locations (seen as stressful), and that they were unable to select the type of signal they reported reacting to. In our study we used mobile exposure units that allow double-blind exposure conditions with personalised exposure settings (signal type, strength, duration) at home. Our aim was to evaluate whether subjects were able to identify exposure conditions, and to assess if providing feedback on personal test results altered the level of self-reported EHS. We used double-blind randomised controlled exposure testing with questionnaires at baseline, immediately before and after testing, and at two and four months post testing. Participants were eligible if they reported sensing either radiofrequency or extremely low frequency fields within minutes of exposure. Participants were visited at home or another location whe...
2007 IEEE Antennas and Propagation International Symposium, 2007
ABSTRACT This article demonstrates the capability of using the finite-differences time-domain (FD... more ABSTRACT This article demonstrates the capability of using the finite-differences time-domain (FDTD) method as simulation tool for optimizing the design of an antenna. The FDTD simulation method is locally enhanced with subcell modeling techniques, which incorporates a-priori known field behavior in (1) curved material interfaces and (2) strong field gradients near sharp metal edges. Combining the FDTD subcell modeling technique with a FDTD simulation hardware acceleration card enables the efficient optimization of several parameters based on genetic algorithms. The ongoing work targets the improved optimization of commercial CAD based mobile phones.
ABSTRACT This article demonstrates the capability of using the finite-differences time-domain (FD... more ABSTRACT This article demonstrates the capability of using the finite-differences time-domain (FDTD) method as simulation tool for optimizing the design of an antenna. The FDTD simulation method is locally enhanced with subcell modeling technique, which incorporates a-priori known field behavior in (1) curved material interfaces and (2) strong field gradients near sharp metal edges. Combining the FDTD subcell modeling technique with a FDTD simulation hardware acceleration card enables the efficient optimization of several parameters based on genetic algorithms.
We describe a method to correlate E-fields induced by exposure to extremely low frequency magneti... more We describe a method to correlate E-fields induced by exposure to extremely low frequency magnetic fields in laboratory mice and rats during in vivo experiments to those induced in children. Four different approaches of mapping relative dose rates between humans and rodents are herein proposed and analyzed. Based on these mapping methods and volume averaging guidelines published by the International Commission on Non-Ionizing Radiation Protection (ICNRP) in 2010, maximum and median induced field values for whole body and for tissues of children and rodents were evaluated and compared. Median induced electric fields in children younger than 10 years old are in the range 5.9-8.5 V/m per T (±0.4 dB). Maximum induced electric fields, generally in the skin, are between 48 V/m and 228 V/m per T (±4 dB). To achieve induced electric fields of comparable magnitude in rodents, external magnetic field must be increased by a factor of 4.0 (±2.6 dB) for rats and 7.4 (±1.8 dB) for mice. Meanwhile...
The Recommendation 1999/529/EU and the Directive 2013/35/EU suggest limits for both general publi... more The Recommendation 1999/529/EU and the Directive 2013/35/EU suggest limits for both general public and occupational exposures to extremely low-frequency magnetic fields, but without special limits for pregnant women. This study aimed to assess the compliance of pregnant women to the current regulations, when exposed to uniform MF at 50 Hz (100 μT for EU Recommendation and 1 and 6 mT for EU Directive). For general public, exposure of pregnant women and fetus always resulted in compliance with EU Recommendation. For occupational exposures, (1) Electric fields in pregnant women were in compliance with the Directive, with exposure variations due to fetal posture of <10 %, (2) electric fields in fetuses are lower than the occupational limits, with exposure variations due to fetal posture of >40 % in head tissues, (3) Electric fields in fetal CNS tissues of head are above the ICNIRP 2010 limits for general public at 1 mT (in 7 and 9 months gestational age) and at 6 mT (in all gestat...
2011 International Conference on Electromagnetics in Advanced Applications
This paper presents preliminary evaluation of the hybrid parallelization of the Finite-Difference... more This paper presents preliminary evaluation of the hybrid parallelization of the Finite-Difference Time-Domain (FDTD) method based on Open Computing Language (OpenCL) and the Message Passing Interface (MPI). Due to the portability of OpenCL, developed code targets not only distributed shared memory computer clusters based on multi-core central processing units (CPUs), but also clusters accelerated by graphics processing units (GPUs). The computational domain is decomposed along the slowest direction, and electromagnetic field boundary data is shared between neighboring subdomains using either OpenCL or MPI communication. The communication overhead between GPUs is proportional to the area of the boundary and represents the rate-limiting step of the method. This paper subsequently shows results of numerical tests aimed at evaluation of the hybrid OpenCL-MPI FDTD solver in electromagnetic simulations.
1999 International Symposium on Electromagnetic Compatibility (IEEE Cat. No.99EX147)
The necessity of near-field evaluation in wireless product development will strongly grow in the ... more The necessity of near-field evaluation in wireless product development will strongly grow in the coming years, since far-field evaluations provide insufficient information for analyzing and optimizing the performance of transmitters operating in complex environments. The objective of this paper is to review the latest progress in near-field measurement technology and to discuss future needs.
2013 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium)
ABSTRACT form only given. While contact-less power charging is becoming a popular feature in mode... more ABSTRACT form only given. While contact-less power charging is becoming a popular feature in modern electronic devices, the exposure to a nearby user from a wireless power transfer (WPT) system should be assessed prior to the commercial availability of such systems. In this study, a 4-link 100 kHz magnetically resonant low power wireless charging system is investigated with respect to the exposure of a user hand. Numerical dosimetry techniques are employed to compute the peak induced spatially averaged electric field (E-field) and specific absorption rate (SAR) in a high-resolution anatomically realistic hand model (based on an adult male hand). The computed peak values are analyzed with respect to the exposure limits recommended by the ICNIRP and IEEE exposure guidelines and standards (i.e., ICNIRP-2010, IEEE C95.6-2002 and IEEE C95.1-2005) to determine the compliance of the investigated WPT system and to derive the critical system parameters which could be adjusted to improve the design of a WPT system. A generic coil analysis is conducted by modelling a single circular coil with diameter in the range of 40 to 240 mm. An anatomical hand model, discretized with a uniform 1 mm grid resolution, is placed 1 mm above the coil with the center of the palm facing the center of the coil. The peak spatially averaged E-field (volume averaged for ICNIRP and line averaged for IEEE) values are plotted with the peak SAR (averaged over 1 gram or 10 gram) values to derive the transition frequency, above which, the peak spatial SAR becomes more dominant than the peak induced E-field for an exposure compliance assessment. This transition frequency can be regarded as the optimum operating frequency which leads to the highest output power of a WPT system with respect to the relevant exposure limits. Subsequently, the 4-link 100 kHz WPT system is modelled to facilitate the exposure analysis of an actual wireless charging system. This study provides the frequency-dependent user hand exp- sure characteristics of a generic circular coil and the exposure analysis of a practical wireless charging system. The computational results indicate that the optimum operating frequency of a WPT system with coil dimensions in the range of 40 mm to 240 mm diameter is approximately 1 MHz based on the peak 2×2×2 mm3 volume averaged E-field and 10 gram averaged SAR values. The investigated 4-link 100 kHz WPT system is found to be compliant with the ICNIRP and IEEE exposure limits while operating with a 5W output power.
Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology, 2017
Results from recent studies suggest that extremely low frequency magnetic fields (ELF-MF) interfe... more Results from recent studies suggest that extremely low frequency magnetic fields (ELF-MF) interfere with intracellular signaling pathways related to proliferative control. The mitogen-activated protein kinases (MAPKs), central signaling components that regulate essentially all stimulated cellular processes, include the extracellular signal-regulated kinases 1/2 (ERK1/2) that are extremely sensitive to extracellular cues. Anti-phospho-ERK antibodies serve as a readout for ERK1/2 activation and are able to detect minute changes in ERK stimulation. The objective of this study was to explore whether activation of ERK1/2 and other signaling cascades can be used as a readout for responses of a variety of cell types, both transformed and non-transformed, to ELF-MF. We applied ELF-MF at various field strengths and time periods to eight different cell types with an exposure system housed in a tissue culture incubator and followed the phosphorylation of MAPKs and Akt by western blotting. We f...
Extreme broadband wireless devices operating above 10 GHz may transmit data in bursts of a few mi... more Extreme broadband wireless devices operating above 10 GHz may transmit data in bursts of a few milliseconds to seconds. Even though the time- and area-averaged power density values remain within the acceptable safety limits for continuous exposure, these bursts may lead to short temperature spikes in the skin of exposed people. In this paper, a novel analytical approach to pulsed heating is developed and applied to assess the peak-to-average temperature ratio as a function of the pulse fraction α (relative to the averaging time [INCREMENT]T; it corresponds to the inverse of the peak-to-average ratio). This has been analyzed for two different perfusion-related thermal time constants (τ1 = 100 s and 500 s) corresponding to plane-wave and localized exposures. To allow for peak temperatures that considerably exceed the 1 K increase, the CEM43 tissue damage model, with an experimental-data-based damage threshold for human skin of 600 min, is used to allow large temperature oscillations t...
Radiofrequency radiation (RFR) causes heating, which can lead to detrimental biological effects. ... more Radiofrequency radiation (RFR) causes heating, which can lead to detrimental biological effects. To characterize the effects of RFR exposure on body temperature in relation to animal size and pregnancy, a series of short-term toxicity studies was conducted in a unique RFR exposure system. Young and old B6C3F1 mice and young, old, and pregnant Harlan Sprague-Dawley rats were exposed to Global System for Mobile Communication (GSM) or Code Division Multiple Access (CDMA) RFR (rats = 900 MHz, mice = 1,900 MHz) at specific absorption rates (SARs) up to 12 W/kg for approximately 9 h a day for 5 days. In general, fewer and less severe increases in body temperature were observed in young than in older rats. SAR-dependent increases in subcutaneous body temperatures were observed at exposures ≥6 W/kg in both modulations. Exposures of ≥10 W/kg GSM or CDMA RFR induced excessive increases in body temperature, leading to mortality. There was also a significant increase in the number of resorptio...
We report a noninvasive strategy for electrically stimulating neurons at depth. By delivering to ... more We report a noninvasive strategy for electrically stimulating neurons at depth. By delivering to the brain multiple electric fields at frequencies too high to recruit neural firing, but which differ by a frequency within the dynamic range of neural firing, we can electrically stimulate neurons throughout a region where interference between the multiple fields results in a prominent electric field envelope modulated at the difference frequency. We validated this temporal interference (TI) concept via modeling and physics experiments, and verified that neurons in the living mouse brain could follow the electric field envelope. We demonstrate the utility of TI stimulation by stimulating neurons in the hippocampus of living mice without recruiting neurons of the overlying cortex. Finally, we show that by altering the currents delivered to a set of immobile electrodes, we can steerably evoke different motor patterns in living mice.
Extremely-low-frequency magnetic fields (ELF-MF) have been classified as "possibly carcinoge... more Extremely-low-frequency magnetic fields (ELF-MF) have been classified as "possibly carcinogenic" to humans on the grounds of an epidemiological association of ELF-MF exposure with an increased risk of childhood leukaemia. Yet, underlying mechanisms have remained obscure. Genome instability seems an unlikely reason as the energy transmitted by ELF-MF is too low to damage DNA and induce cancer-promoting mutations. ELF-MF, however, may perturb the epigenetic code of genomes, which is well-known to be sensitive to environmental conditions and generally deranged in cancers, including leukaemia. We examined the potential of ELF-MF to influence key epigenetic modifications in leukaemic Jurkat cells and in human CD34+ haematopoietic stem cells undergoing in vitro differentiation into the neutrophilic lineage. During granulopoiesis, sensitive genome-wide profiling of multiple replicate experiments did not reveal any statistically significant, ELF-MF-dependent alterations in the pat...
Previous provocation experiments with persons reporting electromagnetic hypersensitivity (EHS) ha... more Previous provocation experiments with persons reporting electromagnetic hypersensitivity (EHS) have been criticised because EHS persons were obliged to travel to study locations (seen as stressful), and that they were unable to select the type of signal they reported reacting to. In our study we used mobile exposure units that allow double-blind exposure conditions with personalised exposure settings (signal type, strength, duration) at home. Our aim was to evaluate whether subjects were able to identify exposure conditions, and to assess if providing feedback on personal test results altered the level of self-reported EHS. We used double-blind randomised controlled exposure testing with questionnaires at baseline, immediately before and after testing, and at two and four months post testing. Participants were eligible if they reported sensing either radiofrequency or extremely low frequency fields within minutes of exposure. Participants were visited at home or another location whe...
2007 IEEE Antennas and Propagation International Symposium, 2007
ABSTRACT This article demonstrates the capability of using the finite-differences time-domain (FD... more ABSTRACT This article demonstrates the capability of using the finite-differences time-domain (FDTD) method as simulation tool for optimizing the design of an antenna. The FDTD simulation method is locally enhanced with subcell modeling techniques, which incorporates a-priori known field behavior in (1) curved material interfaces and (2) strong field gradients near sharp metal edges. Combining the FDTD subcell modeling technique with a FDTD simulation hardware acceleration card enables the efficient optimization of several parameters based on genetic algorithms. The ongoing work targets the improved optimization of commercial CAD based mobile phones.
ABSTRACT This article demonstrates the capability of using the finite-differences time-domain (FD... more ABSTRACT This article demonstrates the capability of using the finite-differences time-domain (FDTD) method as simulation tool for optimizing the design of an antenna. The FDTD simulation method is locally enhanced with subcell modeling technique, which incorporates a-priori known field behavior in (1) curved material interfaces and (2) strong field gradients near sharp metal edges. Combining the FDTD subcell modeling technique with a FDTD simulation hardware acceleration card enables the efficient optimization of several parameters based on genetic algorithms.
We describe a method to correlate E-fields induced by exposure to extremely low frequency magneti... more We describe a method to correlate E-fields induced by exposure to extremely low frequency magnetic fields in laboratory mice and rats during in vivo experiments to those induced in children. Four different approaches of mapping relative dose rates between humans and rodents are herein proposed and analyzed. Based on these mapping methods and volume averaging guidelines published by the International Commission on Non-Ionizing Radiation Protection (ICNRP) in 2010, maximum and median induced field values for whole body and for tissues of children and rodents were evaluated and compared. Median induced electric fields in children younger than 10 years old are in the range 5.9-8.5 V/m per T (±0.4 dB). Maximum induced electric fields, generally in the skin, are between 48 V/m and 228 V/m per T (±4 dB). To achieve induced electric fields of comparable magnitude in rodents, external magnetic field must be increased by a factor of 4.0 (±2.6 dB) for rats and 7.4 (±1.8 dB) for mice. Meanwhile...
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Papers by Niels Kuster