Radiofrequency Field Research Articles

Coherent dressing of ground-state spin in a thermal atomic ensemble

Dressed states are eigenstates of the full Hamiltonian which also includes the interaction of the atoms with the driving field. From this point of view, photons of the field interacting with the atom externally induce quantum coherence, and thus modify the inherent properties of atomic system, such as Mollow triplets in the resonance fluorescence spectrum. Because of the rigorous requirement on the ratio of driving strength to the intrinsic linewidth, the associated demonstrations in neutral atoms are restricted to optical dressing in a cavity quantum electrodynamics system and microwave dressing in the Rydberg excitation. Here, we report the realization of coherent dressing of a ground state driven by a radio-frequency magnetic field in an antirelaxation coated warm vapor cell. We reveal the properties of the radio-frequency dressed states, a linear scaling in the resonance splitting, and the improved resonance linewidth. Such a system is robust to the variation of detection frequency and atom number and is able to determine the driving frequency. It thus may emerge as a unique and versatile tool in quantum metrology, for instance, rf atomic magnetometry in a large detection frequency range. Published by the American Physical Society 2024

Features of Formation of Electromagnetic Fields of Industrial and Radio-Frequency Ranges in the Conditions of the Modern Residential Development of High Number of Storeys

The tool research of electromagnetic fields of industrial frequency and radio-frequency range in by Murino of the Leningrad Region is executed. Steady excesses of admissible level of tension on borders of a sanitary rupture of the high-voltage line of 330 kV are revealed. Excesses of admissible levels of magnetic induction and in the radio-frequency range – energy stream density are not revealed. It is established that the difference of values of electric field strength in 1.8 m from a surface and at the height of 72 m reaches 1–2 orders that can be explained only with the grounding Earth’s surface role. Considerable divergences of the settlement and measured values of tension and magnetic induction are revealed that means insufficiently correct account when calculating electrophysical properties of air. The detailed cards of density of a stream of energy showing a difficult, but steady picture of distribution of values are created. Some elements of territorial structure of electromagnetic fields of radio-frequency range – fragments of rings around base stations of cellular communication, and the auras dated for certain houses are revealed.

Preclinical validation of a metasurface-inspired conformal elliptical-cylinder resonator for wrist MRI at 1.5 T

ObjectiveTo design a metasurface-inspired conformal elliptical-cylinder resonator (MICER) for wrist magnetic resonance imaging at 1.5 T and evaluate its potential for clinical applications. MethodsAn electromagnetic simulation was used to characterize the effect of MICER on radio frequency fields. A phantom and 14 wrists from 7 healthy volunteers were examined using a 1.5 T MRI system. The examination included T1-weighted spin echo, fat-saturation proton density-weighted fast spin echo, and three-dimensional T1-weighted gradient echo sequences. All scans were repeated using two methods: MICER combined with the spinal coil, which is a surface coil built-in examination table, and the 12-channel wrist array coil, to receive signals. Image signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated, and the differences between the two methods were compared using a paired Student's t-test. ResultsIn the phantom study, the image obtained with MICER had a higher SNR compared to the image obtained with the 12-channel wrist coil. Almost all wrist tissues showed a higher SNR on the images obtained with MICER than on the images obtained with the 12-channel wrist coil (P < 0.05). And the CNR between wrist tissues on images obtained with MICER was higher than that obtained with the 12-channel wrist coil (P < 0.05). ConclusionsThe quality of the MRI using MICER is superior to that of the commercially available 12-channel wrist coil, indicating its potential value for clinical practice.

Evolution of Electrothermal Heating and Dielectric Properties of Phenolic Resins During Pyrolysis

AbstractElectrothermal heating generated via radio frequency (RF) fields is used to probe the transformation of phenolic resin to a carbon matrix during pyrolysis. Phenolic resin is a single‐stage thermoset that is popular due to its heat resistance, chemical resistance, high strength, and low creep properties. When phenolic resin is subjected to high‐temperature, low‐oxygen treatment (pyrolysis), it is converted to a carbon material useful for many structural applications. Here, neat phenolic resin is pyrolyzed at different temperatures, and the heating response of the newly formed carbon material is tracked when exposed to an RF field. The electrical conductivity of the matrix increased with increasing pyrolysis temperature, with ≈10−4 S m−1 for the neat sample prior to pyrolysis, and ≈102 S m−1 for the sample pyrolyzed at 850 °C. The material's electrothermal response to applied RF fields increases as the material pyrolyzes and becomes conductive; however, at high pyrolysis temperatures, the material becomes sufficiently conductive such that the RF fields are reflected rather than absorbed, and the heating response decreases. The findings of this work show that heating response to RF fields can be used as a quick and easy characterization technique for tracking structural changes associated with phenolic pyrolysis.

Low-power WALTZ decoupling under magic-angle spinning NMR

Abstract. Heteronuclear low-power decoupling using the solution-state wideband alternating-phase low-power technique for zero-residual splitting (WALTZ) sequences has become quite popular in solid-state protein NMR and seems to work well. However, there are no systematic studies that characterize these sequences under magic-angle spinning (MAS) and give recommendations on which parameter should be used. We have studied in detail the use of WALTZ-16 and WALTZ-64 as low-power decoupling sequences under 100 kHz MAS by characterizing the resonance conditions analytically using numerical simulations and experiments on model substances. The recoupling heteronuclear resonance conditions between the modulation frequency of the sequences and the MAS frequency is the most important feature. Pulse lengths corresponding to areas with vanishing first-order heteronuclear recoupling are good candidates for efficient decoupling. We have characterized two such conditions which can be defined using the nutation frequency of the radio frequency (RF) field (ν1) and the spinning frequency (νr) by ν1=νr/10 and ν1=2νr/5, which both lead to narrow lines and are stable against RF-field variations and chemical-shift offsets. More such conditions might exist but were not investigated here.

Hybrid Paul-optical trap with large optical access for levitated optomechanics

We present a hybrid trapping platform that allows us to levitate a charged nanoparticle in high vacuum using either optical fields, radio-frequency fields, or a combination thereof. Our hybrid approach combines an optical dipole trap with a linear Paul trap while maintaining a large numerical aperture (0.77 NA). We detail a controlled transfer procedure that allows us to use the Paul trap as a “safety net” to recover particles lost from the optical trap at high vacuum. The presented hybrid platform adds to the toolbox of levitodynamics and represents an important step towards fully controllable “dark” potentials, providing control in the absence of decoherence because of photon recoil. Published by the American Physical Society 2024

Abstract 4119611: Catheter ablation approach and outcome in HIV+ patients with atrial fibrillation: a systematic review and meta-analysis

Background: Catheter ablation has emerged as an effective treatment option for atrial fibrillation (AF) in the general population. However, limited data exist on the outcomes of catheter ablation in patients infected with the Human Immunodeficiency Virus (HIV+) with concomitant AF. Objectives: This systematic review and single arm meta-analysis aims to comprehensively evaluate the literature on catheter ablation approach and outcome in HIV+ patients with AF. Methods: A systematic search of PubMed, Embase, and Cochrane Central Register of Controlled Trials was conducted following PRISMA guidelines.Studies meeting the intervention of catheter ablation for AF in HIV+ patients, using radiofrequency, cryoballoon, or pulsed field ablation techniques, were included and data were collected and synthesized using proportion meta-analysis techniques. Statistical analysis was carried out using R software. Results: Three studies met the inclusion criteria, involving 89 HIV+ patients, with an average age of 51.5 years, of whom 83.1% were men, undergoing catheter ablation. Two studies performed received isolation of the pulmonary vein (PV) + posterior wall and superior vena cava. And one study evaluated only the isolation of the pulmonary veins. Of these patients, 43.8% had paroxysmal AF and 56.1% had persistent AF. In two studies reporting freedom from atrial arrhythmias, all patients (62) experienced recurrence of atrial arrhythmias within 5 years of follow-up. Freedom from repeat ablation was 6.26% (Figure 1A). The rate of Pulmonary Vein Trigger was 31.28% (Figure 1B), while the rate of Non-Pulmonary Vein Trigger (non-PV) was 76.64% (Figure 1C). Conclusion: In this systematic review and meta-analysis assessing outcomes of ablation in HIV patients with AF, we observed a similar prevalence of paroxysmal and persistent AF. Furthermore, contrary to the non-HIV+ patients, a high incidence of non-pulmonary vein triggers of AF was noted in this population.

Physical therapy approach and non-invasive modalities in treatment of vaginal laxity: a literature review.

Pelvic floor physical therapy (PFPT) and noninvasive modalities can be more safe and available treatments for vaginal laxity (VL) with less risk of postsurgical complications. The purpose of this review is to define the concepts of PFPT and noninvasive modalities, examine the evidence supporting those modalities as a treatment for VL, and evaluate their effectiveness. Between 2002 and 2023, clinical studies including women diagnosed with VL were examined in the Web of Science, Cochrane Library, Scopus, and PubMed databases. Exclusion criteria included studies with no outcomes or inadequate data, procedures, suggestions, editorials, book chapters, letters to editors, reviews, meta-analyses, animal research, and articles in languages other than English. Only seventeen studies have been identified. Four studies have demonstrated the impact of PFPT (low- and medium-energy radiofrequency (RF), ultrasound, low-energy laser treatment, par sacral stimulation, the knack method, and pelvic floor exercises), and thirteen studies have discussed the impact of noninvasive modalities (RF, combined multipolar RF with pulsed electromagnetic, combined RF and pulsed electromagnetic field, high-intensity focused ultrasound, CO2 laser, combining multipolar RF and hybrid fractional laser, microfocused ultrasound, and the VIVEVE surface-cooled RF) on vaginal laxity. This review indicates many knowledge areas that must be attempted in order to understand the influence of nonstrengthening physical therapy and noninvasive methods on vaginal laxity. In addition to the mechanisms behind their impacts. In addition, we strongly recommend that more clinical trials of high methodological and interventional quality are required to investigate the efficacy of various physical therapy approaches, including electrical stimulation, biofeedback exertion, acupressure, manual therapy, neuromodulation, core exercise therapy, hydrotherapy, well-designed ultrasound therapy protocols, and vaginal weight training.

Continuous broadband Rydberg receiver using AC Stark shifts and Floquet states

We demonstrate the continuous broadband microwave receivers based on AC Stark shifts and Floquet states of Rydberg levels in a cesium atomic vapor cell. The resonant transition frequency of two adjacent Rydberg states 78 S1/2 and 78 P1/2 is tuned based on AC Stark effect of 70 MHz radio frequency (RF) field that is applied outside the vapor cell. The use of the j=1/2 Rydberg states ensures that only a single mj sublevel is involved. The generated Rydberg Floquet states act to enhance the sensitivity of the AC-Stark-tuned states when the frequency is matched and further extend the bandwidths. We achieve microwave field measurements with over 1.172 GHz continuous frequency tuning and a sensitivity ranging from 280.2 nVcm−1Hz−1/2 to 14.6 μ Vcm−1Hz−1/2. The achieving of continuous frequency and high sensitivity microwave detection will promote the application of Rydberg receivers in the radar technique and wireless communication.

Electromagnetic exposure of population in three cities of Romania at four years difference, based on data recorded by the fixed national radiofrequency monitoring network

Abstract The blooming of wireless technologies and the deployment of the fifth generation (5G) of mobile communications have been accompanied by a significant increase in the risk perception related to human exposure to radio-frequency electromagnetic field (RF-EMF). Therefore, EMF monitoring has become necessary in areas with increased densification of the EMF sources. Present work made use of the raw data kindly provided by the National Authority for Management and Regulation in Communications (ANCOM) in Romania from the fixed EMF sensor network nationally deployed. We aimed to analyze the case of electric field level evolution after four years, in three cities. In each city a single monitoring station was chosen in the analysis. Database in the wide- and narrow-bandwidths covering the range (100 kHz – 7 GHz) was processed for whole years 2019 and 2023. Comparisons between locations and years were enabled by means of: a) descriptive statistics; b) time series analysis with Poincare plots for time-variability characterization; c) recurrence quantification analysis to emphasize the nonlinear dynamics of the exposure levels, respectively the recurring exposure levels dynamics. Similarities and dissimilarities were observed and discussed.

Modulation influence on power deposition inside a human head model exposed to 3.5 GHz plane wave

Abstract Biological effects of radiofrequency fields remain one major subject of interest, with the continuous development of communication technologies and their more and more intensive use. Many authors have discussed the special role that modulation has on the produced effect, comparatively to continuous wave. Numerical dosimetric studies following the differences in power deposition in tissues, in function of the applied waveform, are scarce. Here, we analyse by numerical dosimetry, the specific absorption rate (SAR) of energy absorbed in a human head model when a plane wave, either a continuous one or two modulated ones (amplitude-modulated and quadrature amplitude modulated) are impinging the head, from frontal or lateral directions. The final objective was to emphasize the differences, based on average, peak values, or tissue-specific values of SAR. In all investigated cases the carrier frequency was 3.5 GHz, which belongs to the 5G mobile communications in the FR1 band. The computations were made in the case of the same total incident energy delivered per each modulation considered.

Biomarkers in early and late period after radiofrequency and pulsed field catheter ablation of atrial fibrillation

Abstract Introduction Biomarkers are routinely used parameters for disease diagnosis, treatment control and risk stratification. In connection with atrial fibrillation (AF), the importance of GDF-15 (growth differentiation factor 15), NT-proBNP (N-terminal fragment brain natriuretic factor) and hs-TnT (high sensitivity cardiac troponin T) is discussed. Catheter ablation is an established treatment method in selected population with AF. However, biomarker response to radiofrequency catheter ablation (RFCA) and pulsed field ablation (PFA) of AF has not been precisely described. Purpose Purpose of the study was to describe early and late dynamics of GDF-15, hs-TnT and NT-proBNP in different ablation technologies. Methods We prospectively enrolled 48 patients (median (IQR) age 62 (55; 70) years, 30 males) undergoing RFCA, which we compared with 30 patients (median (IQR) age 64 (56; 71) years, 18 males) undergoing PFA. All patients underwent 6 sequential blood takes: before ablation (baseline), right after ablation (0h), 24 and 48 hours after procedure (24h and 48h), 90 and 180 days after procedure. Levels of GDF-15, hs-TnT and NT-proBNP were analyzed. Results Out of all patients, 19 (40 %) and 20 (67 %) patients had paroxysmal AF in RFCA and PFA group, respectively. Additional ablation lesions over pulmonary vein isolation were done in 26 (54 %) patients in RFCA group and 11 (43 %) patients in PFA group. Median procedural time was significantly longer in RFCA than in PFA group (155 (130; 190) vs. 80 (70; 90) min; p &amp;lt; 0.01). Early dynamics of GDF-15 and cardiac hs-TnT are visualised in Figure 1 and 2. GDF-15 level peak was registered 48 hours after ablation with median (IQR) 1183 (824; 1988) ng/l. Compared to baseline, GDF-15 values sustained elevated up to 90 days after ablation in both groups and decreased to baseline levels after 180 days. No significant differences were found in GDF-15 levels between patients treated with RFCA and PFA. Maximal values of hs-TnT were significantly higher in PFA group than in RFCA group (1001±589 vs. 458±202 ng/l; p &amp;lt; 0.001). We have recognised decrease of NT-proBNP between baseline and 90 days after procedure in both groups: 338 (112; 613) vs. 209 (101; 545) ng/l; p &amp;lt; 0.05. Conclusion Eventhough GDF-15 is considered as a nonspecific biomarker reflecting general condition of patient, the levels are significantly affected by catheter ablation of AF for several months irrespective to ablation technology. PFA is associated with advanced elevation of hs-TnT.Dynamics of GDF-15 (median; IQR)Dynamics of hs-TnT (median; IQR)

Extending radiowave frequency detection range with dressed states of solid-state spin ensembles

Quantum sensors using solid-state spin defects excel in the detection of radiofrequency (RF) fields, serving various applications in communication, ranging, and sensing. For this purpose, pulsed dynamical decoupling (PDD) protocols are typically applied, which enhance sensitivity to RF signals. However, these methods are limited to frequencies of a few megahertz, which poses a challenge for sensing higher frequencies. We introduce an alternative approach based on a continuous dynamical decoupling (CDD) scheme involving dressed states of nitrogen vacancy (NV) ensemble spins driven within a microwave resonator. We compare the CDD methods to established PDD protocols and demonstrate the detection of RF signals up to ~85 MHz, about ten times the current limit imposed by the PDD approach under identical conditions. Implementing the CDD method in a heterodyne/synchronized protocol combines the high-frequency detection with high spectral resolution. This advancement extends to various domains requiring detection in the high frequency (HF) and very high frequency (VHF) ranges of the RF spectrum, including spin sensor-based magnetic resonance spectroscopy at high magnetic fields.

In vivo imaging of the human brain with the Iseult 11.7-T MRI scanner.

The understanding of the human brain is one of the main scientific challenges of the twenty-first century. In the early 2000s, the French Atomic Energy Commission launched a program to conceive and build a human magnetic resonance imaging scanner operating at 11.7 T. We have now acquired human brain images in vivo at such a magnetic field. We deployed parallel transmission tools to mitigate the radiofrequency field inhomogeneity problem and tame the specific absorption rate. The safety of human imaging at such high field strength was demonstrated using physiological, vestibular, behavioral and genotoxicity measurements on the imaged volunteers. Our technology yields T2 and T2*-weighted images reaching mesoscale resolutions within short acquisition times and with a high signal and contrast-to-noise ratio.

Performance of a Radio-Frequency Two-Photon Atomic Magnetometer in Different Magnetic Induction Measurement Geometries.

Measurements monitoring the inductive coupling between oscillating radio-frequency magnetic fields and objects of interest create versatile platforms for non-destructive testing. The benefits of ultra-low-frequency measurements, i.e., below 3 kHz, are sometimes outweighed by the fundamental and technical difficulties related to operating pick-up coils or other field sensors in this frequency range. Inductive measurements with the detection based on a two-photon interaction in rf atomic magnetometers address some of these issues as the sensor gains an uplift in its operational frequency. The developments reported here integrate the fundamental and applied aspects of the two-photon process in magnetic induction measurements. In this paper, all the spectral components of the two-photon process are identified, which result from the non-linear interactions between the rf fields and atoms. For the first time, a method for the retrieval of the two-photon phase information, which is critical for inductive measurements, is also demonstrated. Furthermore, a self-compensation configuration is introduced, whereby high-contrast measurements of defects can be obtained due to its insensitivity to the primary field, including using simplified instrumentation for this configuration by producing two rf fields with a single rf coil.

Frequency-Dependent Antioxidant Responses in HT-1080 Human Fibrosarcoma Cells Exposed to Weak Radio Frequency Fields.

This study explores the complex relationship between radio frequency (RF) exposure and cancer cells, focusing on the HT-1080 human fibrosarcoma cell line. We investigated the modulation of reactive oxygen species (ROS) and key antioxidant enzymes, including superoxide dismutase (SOD), peroxidase, and glutathione (GSH), as well as mitochondrial superoxide levels and cell viability. Exposure to RF fields in the 2-5 MHz range at very weak intensities (20 nT) over 4 days resulted in distinct, frequency-specific cellular effects. Significant increases in SOD and GSH levels were observed at 4 and 4.5 MHz, accompanied by reduced mitochondrial superoxide levels and enhanced cell viability, suggesting improved mitochondrial function. In contrast, lower frequencies like 2.5 MHz induced oxidative stress, evidenced by GSH depletion and increased mitochondrial superoxide levels. The findings demonstrate that cancer cells exhibit frequency-specific sensitivity to RF fields even at intensities significantly below current safety standards, highlighting the need to reassess exposure limits. Additionally, our analysis of the radical pair mechanism (RPM) offers deeper insight into RF-induced cellular responses. The modulation of ROS and antioxidant enzyme activities is significant for cancer treatment and has broader implications for age-related diseases, where oxidative stress is a central factor in cellular degeneration. The findings propose that RF fields may serve as a therapeutic tool to selectively modulate oxidative stress and mitochondrial function in cancer cells, with antioxidants playing a key role in mitigating potential adverse effects.

Effects of 4.9 GHz Radiofrequency Field Exposure on Brain Metabolomic and Proteomic Characterization in Mice.

Electromagnetic exposure has become increasingly widespread, and its biological effects have received extensive attention. The purpose of this study was to explore changes in the metabolism profile of the brain and serum and to identify differentially expressed proteins in the brain after exposure to the 4.9 GHz radiofrequency (RF) field. C57BL/6 mice were randomly divided into a Sham group and an RF group, which were sham-exposed and continuously exposed to a 4.9 RF field for 35 d, 1 h/d, at an average power density (PD) of 50 W/m2. After exposure, untargeted metabolomics and Tandem Mass Tags (TMT) quantitative proteomics were performed. We found 104 and 153 up- and down-regulated differentially expressed metabolites (DEMs) in the RF_Brain group and RF_Serum group, and the DEMs were significantly enriched in glycerophospholipid metabolism. Moreover, 10 up-regulated and 51 down-regulated differentially expressed proteins (DEPs) were discovered in the RF group. Functional correlation analysis showed that most DEMs and DEPs showed a significant correlation. These results suggested that 4.9 GHz exposure induced disturbance of metabolism in the brain and serum, and caused deregulation of proteins in the brain.

Radiofrequency field inhibits RANKL-induced osteoclast differentiation in RAW264.7 cells via modulating the NF-κB signaling pathway

ABSTRACT In this study, we investigated the inhibitory effects of radiofrequency exposure on RANKL-induced osteoclast differentiation in RAW264.7 cells, along with the underlying mechanisms. RAW264.7 cells were subjected to radiofrequency exposure at three distinct power densities: 50 µW/cm2, 150 µW/cm2, and 450 µW/cm2. The results showed that, among the three dosage levels, exposure to 150 µW/cm2 of radiofrequency radiation significantly reduced the proliferation capacity of RAW264.7 cells. RF exposure at three power densities resulted in significant increases in the level of osteoclast apoptosis and notable decreases in osteoclast differentiation. Notably, the most pronounced effects on apoptosis, differentiation in RAW 264.7 cells were observed at the 150 µW/cm2 power density. These effects were accompanied by concurrent decreases in mRNA and protein levels of osteoclast-specific genes, including RANK, NFATc1, and TRACP. Furthermore, radiofrequency exposure at power density of 150 µW/cm2 induced a significant decrease in cytoplasmic NF-κB protein levels while increasing its nuclear fraction, thereby counteracting the effects of RANKL-induced NF-κB activation. These data suggest that radiofrequency exerts inhibitory properties on RANKL-induced NF-κB transcriptional activity, subsequently indirectly suppressing the expression of downstream NF-κB target genes, such as NFATc1 and TRACP. In conclusion, our study demonstrates that radiofrequency radiation effectively inhibits osteoclast differentiation by modulating the NF-κB signaling pathway. These findings have important implications for potential therapeutic interventions in osteoporosis.

An MTCA-based LLRF prototype system of LINAC in Hefei Advanced light facility

The linear accelerator (LINAC) system currently under construction at the Hefei Advanced Light Facility (HALF) employs acceleration tubes to accelerate the electron beam to 2.2 GeV. The RF field within the acceleration tube is controlled by an MTCA.4-based low-level radio frequency (LLRF) prototype system to meet stringent phase stability requirements. This paper introduces the structure of the LLRF system, encompassing both its hardware and software components. The LLRF system uses the non-IQ-sampling method to suppress odd harmonics through digital filters, achieving a signal-to-noise ratio (SNR) of approximately 73 dB. Given that the power sources of most acceleration tubes operate in a saturated state, the radio-frequency (RF) control algorithm within the software is based on a separate amplitude open-loop and phase close-loop to maintain stable phase control during amplitude disturbances. The design of the RF control logic, including digital filters, the REF phase tracking method, the close-loop feedback controller, and the output pulse mode control algorithm, is detailed. Offline pulse-to-pulse test results demonstrate that it achieves a phase stability of 0.0176° rms with a solid-state amplifier, meeting the facility's requirements.

Vector magnetometry employing a rotating RF field in a single-beam optically pumped magnetometer

Magnetic field vector information is crucial for many advanced applications, such as navigation and biomedical imaging. However, existing methods often lack high sensitivity or require complex setups. This study addresses these challenges by proposing a novel vector magnetometry method using a single-beam optically pumped magnetometer. A rotating radio-frequency field is innovatively utilized to excite atomic spin precession, enabling accurate measurement of the magnetic field direction based on scalar measurement. The method is tested through physical experiments with different magnetic field configurations to validate its performance. The experimental results demonstrate high accuracy, and achieve a magnetic field amplitude sensitivity of 800 fT/Hz1/2, an azimuth sensitivity of 100 μrad/Hz1/2, and a polar angle sensitivity of 13 μrad/Hz1/2. The proposed method facilitates sensor miniaturization and is suitable for applications in high magnetic field environments, such as geomagnetic field.