Static Magnetic Field Strength Research Articles

Mitigation of cadmium toxicity stress by magnetopriming during germination of soybean

Cadmium (Cd) is a highly toxic heavy metal that poses a significant threat to food safety and agricultural production worldwide. Its solubility enables easy entry into plants, leading to reductions in seed germination, growth and crop yield. Thus, it is crucial to discover methods to alleviate the harmful impact of Cd on plant growth. Magnetopriming (MP) is a non-invasive and cost-effective technique that has been proposed to improve plant growth under abiotic stress conditions. The current study investigated the potential of MP to improve the seed germination, early seedling growth and biochemical responses of soybean under Cd toxicity. Soybean seeds were magnetoprimed with static magnetic field (SMF) strength of 200 mT for 1 hour before germination. The unprimed and magnetoprimed seeds were grown under different concentrations of cadmium chloride (0, 25, 50, 75, 100, 200 and 300 μM CdCl2) in Petri plates for five days in the dark at 25 + 1°C. The results revealed that Cd toxicity significantly reduced the germination percentage and inhibited the seedling growth parameters and increased oxidative stress, as determined by malondialdehyde (MDA) content in soybean seedlings from unprimed seeds. The inhibitory effect was increased with increasing concentration of Cd. However, MP remarkably increased the germination percentage, seedling growth parameters, activities of total amylase and protease, and hydrogen peroxide (H2O2) content and decreased MDA and proline content in germinating soybean seedlings at all concentrations of Cd. These findings suggest that MP can alleviate the adverse effects of Cd stress in soybean seedlings and increase the tolerance index towards Cd toxicity by enhancing the activity of amylotic and proteolytic enzymes and reducing oxidative stress.

Study on the effect of static magnetic field strength and arrangement on the working performance of PEMFC with different flow fields

This study explores the impact of magnetic fields on the operation and performance of proton exchange membrane fuel cells (PEMFCs) with various flow fields. Different positions and intensities of magnetic fields were applied to investigate their effects. The performance of PEMFCs with different flow fields was then tested under different magnetic field strengths and arrangements. The experimental results demonstrate that, under the same conditions, the power density of the PEMFCs increases when subjected to magnetic fields of varying strengths (180mT, 220mT, and 260mT) compared to no magnetic field. Furthermore, the maximum power density of the cells increases with higher applied magnetic field strengths. The experiments also compared the performance of the fuel cell's cathode, anode, and bipolar operations with magnetic field arrangements in different flow fields. The results reveal that the performance enhancement of the fuel cell with magnetic field arrangement in the cathode is greater than that with magnetic field arrangement in the anode and bipolar. Specifically, when a magnetic field of 260mT is loaded onto the cathode for fuel cells with parallel, wave, and M−type flow fields, the maximum power density (MPD) increases by 55%, 23.9%, and 23.22%, respectively. In conclusion, the utilization of magnetic fields can enhance the performance of PEMFCs under operating conditions.

Resonating sub-wavelength metallic wires based pads for boosting signal-to-noise ratio of birdcage head coils at 1.5T MRI

Magnetic resonance imaging (MRI) is an increasingly popular non-invasive diagnostic imaging tool in modern healthcare. The signal-to-noise ratio (SNR) of MRI can be improved by locally enhancing radiofrequency (RF) magnetic field using metamaterials — without the need for stepping up static magnetic field strength. However, designing a thin and compact metamaterial-based structure for the most commonly used 1.5T MRI systems (operating at f0∼64MHz) remains highly challenging due to long vaccum wavelength λ0∼4.7m at resonance. The limited free space available inside MRI receive coil arrays (typically 10-20mm) restricts the practical usability of any bulky resonator (with dimensions in order of meters) inside commercial 1.5T MRI head transceiver-coils. In this paper, we design a thin and compact RF metamaterial-based pad comprising dual-layer wire-array resonators that fits in the available space and provides significant magnetic field enhancement at 1.5T MRI. The metamaterial-based pad provides the SNR enhancement by a factor of ∼19, on the surface of bio-model in contact with the pad, as compared to the case without pad while maintaining specific absorption rate well below the standard safety limit. We present an equivalent circuit approach combined with a transformer-based model to compute the SNR enhancement factor of metamaterial-based pad, which adequately explains the underlying physical mechanism of metamaterial’s magnetic resonance and closely estimates our numerical findings. We believe that, when integrated into the clinical 1.5T MRI systems, our proposed metamaterial-based pad can help improve the SNR of head MRI scans, resulting in either higher image quality or reduced scan time.

Optimal design of transducers based on the Halbach arrays permanent magnet structure

ABSTRACT For enhancing the static magnetic field and reducing the size of torsional guided wave magnetostrictive patch transducer (MPT) with permanent magnets, a MPT with Halbach arrays is proposed. The structural parameters design of the MPT can be guided by finite element simulation. It is found that increasing the central angle of the radially magnetised magnets can increase the strength of the static magnetic field, and it can be adjusted through designing the radial size and lift-off distance of the magnets. The Halbach magnet arrays composed of circumferentially magnetised magnets with a circumferential size of 6 mm and radially magnetised magnets with a circumferential size of 4 mm are selected to experimentally compare with the alternating magnetised magnet arrays composed of magnets with a circumferential size of 10 mm. The results show that the static magnetic field strength can be increased by 54.7% using Halbach magnet arrays. The proposed MPT composed of the Halbach magnet arrays and a linear solenoid array can excite and receive T(0,1) guided wave. Compared with the alternating magnetised magnet array MPT, the guided wave signal amplitude is increased by about 70% generated and received by the MPT with the Halbach magnet arrays.

Effect of static magnetic field assisted freezing on the product quality of Korla fragrant pear

AbstractFreezing is a good method of preserving the sensory and nutritional quality of fresh fruits and vegetables. However, big ice crystals always form in a common freezing process which causes mechanical damage to the fruit and vegetable cells and results in low‐quality products. The external magnetic field can interfere with the state of the internal water, thus changing the ice crystal formation process accordingly. It was suggested that suitable magnetic field treatments can affect the biological characteristics of fruits and vegetables and improve the quality of the frozen products. In this experiment, Korla fragrant pear was freezing processed at the different static magnetic field (SMF) strengths (0, 2, 4, 6, 8, and 10 mT), and the pear quality was evaluated by juice loss, color, texture, total soluble solid content and total acid content, water state, and distribution. The results showed that the utilization of SMF in freezing reduced the loss of juice and soluble solids, and maintained the titratable acidity. However, SMFs performed poorly in color and texture protection. This research suggested that magnetic field‐assisted freezing had some positive effects on the quality of frozen Korla fragrant pear, but more works need to be done to further improve the product quality.Practical applicationsThis research emphasizes the positive effect of static magnetic field treatment on improving the freezing rate and optimizing the freezing process of Korla fragrant pear, which also provides a new idea and practical reference for the potential application of static magnetic field in freezing preservation of fruits and vegetables.

Optimized Unilateral Magnetic Resonance Sensor with Constant Gradient and Its Applications in Composite Insulators

In this study, an optimized unilateral magnetic resonance sensor with a three-magnet array is presented for assessing the aging of composite insulators in power grids. The sensor’s optimization involved enhancing the static magnetic field strength and the homogeneity of the RF field while maintaining a constant gradient in the direction of the vertical sensor surface and maximizing homogeneity in the horizontal direction. The center layer of the target area was positioned 4 mm from the coil’s upper surface, resulting in a magnetic field strength of 139.74 mT at the center point of the area, with a gradient of 2.318 T/m and a corresponding hydrogen atomic nuclear magnetic resonance frequency of 5.95 MHz. The magnetic field uniformity over a 10 mm × 10 mm range on the plane was 0.75%. The sensor measured 120 mm × 130.5 mm × 76 mm and weighed 7.5 kg. Employing the optimized sensor, magnetic resonance assessment experiments were conducted on composite insulator samples utilizing the CPMG (Carr–Purcell–Meiboom–Gill) pulse sequence. The T2 distribution provided visualizations of the T2 decay in insulator samples with different degrees of aging.

Influence of static magnetic field on rapid solidified structure and nanocrystallization behavior of Fe–Si–B–Cu soft magnetic alloys with pre-existing α-Fe nanocrystals

The effects of static magnetic field strength on the rapid solidified structure, thermal stability, crystallization structure and soft magnetic properties of melt-spun Fe81.6Si4B13Cu1.4 alloys were investigated and the corresponding related mechanism was discussed in terms of formation of pre-existing α-Fe crystals and nanocrystallization behaviors. The rise of magnetic field strength promotes the formation of the α-Fe crystals in as-spun alloy, enhances the competitive growth between the crystals during annealing, and then refines the crystals in the annealed alloy and improves their magnetic softness. The Fe81.6Si4B13Cu1.4 alloy prepared under 200 mT contains α-Fe crystals with a high number density and average size (D) of 8.3 × 1022 m−3 and 5.9 nm, respectively, in as-spun state, and possesses fine crystals with a D of 18.2 nm and excellent soft magnetic properties with a high saturation magnetization of 1.75 T, low coercivity of 9.2 A/m and high effective permeability of 10,160 at 1 kHz after annealing at 633 K for 60 min.

Effect of StaticMagneticand Pulsated Electromagnetic Fields On the Dynamic and Kinematic Viscosity of Metal Cutting Fluids

In this paper, authors investigated the difference between the influenceof staticmagnetic field and pulsating electromagnetic field on metal cutting fluids. Two essential physical parameters of the cutting fluids, dynamic and kinematic viscosity coefficients were analyzedduring the experiment in the same laboratory condition.The results obtained from the experimental researchshow thatthe influence of thestatic magnetic field onsample metal cutting fluids is greaterthanthe influence ofthe pulsating electromagnetic field.Such as, after magnetizing cutting fluids under the effect of three various static magnetic field strengths, the kinematic and dynamic viscosity havedecreased about 17%and 6% respectively,while they declined about 7% and 4% after magnetizing the fluidsunder the effect of the same electromagnetic magnetic field strengths. Moreover, special magnetizing devices have beendesigned to magnetize different types offluids intheirflowing condition.

Enhancing the Yield Potential of Soybean after Magneto-Priming: Detailed Study on Its Relation to Underlying Physiological Processes

Soybean (Glycine max) is one of the most important proteins and oilseed crops in the world due to a boom in its demand. In order to meet this demand, various modern agricultural methods are being employed, of which magneto-priming (treatment of seeds with magnetic field) is becoming the most popular technique owing to its efficiency and eco-friendly nature to improve seed vigour, growth and yield of soybean plants. Therefore, we conducted a field experiment to evaluate the impact of magneto-priming of seeds with static magnetic field on soybean var. JS-335 plants. We used static magnetic field (SMF) strengths of 150 mT (1 h) and 200 mT (1 h) for this study. Both the SMF treatments improved growth (shoot as well as root growth parameters), carbon fixation (PSII efficiency, gas exchange parameters, carbonic anhydrase activity) and nitrogen fixation (leghemoglobin content, total protein content, nitrate reductase activity). We observed an association between these parameters which contributed to biomass accumulation and hence to the enhanced crop yield. In addition, reduced levels of ASA (reduced form of ascorbate), MDA (malondialdehyde) and antioxidant enzymes suggest that magneto-priming alleviates oxidative stress in SMF-primed soybean plants. Field strength of 200 mT (1 h) proved to be more effective in improving all the parameters as compared to 150 mT. Our study suggested that pre-sowing SMF treatment can be efficaciously employed for improving the growth, development and production of soybean.

A Multi-Pass Optically Pumped Rubidium Atomic Magnetometer with Free Induction Decay.

A free-induction-decay (FID) type optically-pumped rubidium atomic magnetometer driven by a radio-frequency (RF) magnetic field is presented in this paper. Influences of parameters, such as the temperature of rubidium vapor cell, the power of pump beam, and the strength of RF magnetic field and static magnetic field on the amplitude and the full width at half maximum (FWHM) of the FID signal, have been investigated in the time domain and frequency domain. At the same time, the sensitivities of the magnetometer for the single-pass and the triple-pass probe beam cases have been compared by changing the optical path of the interaction between probe beam and atomic ensemble. Compared with the sensitivity of ∼21.2 pT/ in the case of the single-pass probe beam, the amplitude of FID signal in the case of the triple-pass probe beam has been significantly enhanced, and the sensitivity has been improved to ∼13.4 pT/. The research in this paper provids a reference for the subsequent study of influence of different buffer gas pressure on the FWHM and also a foundation for further improving the sensitivity of FID rubidium atomic magnetometer by employing a polarization-squeezed light as probe beam, to achieve a sensitivity beyond the photo-shot-noise level.

Biradical Polarizing Agents at High Fields.

The sensitivity enhancements available from dynamic nuclear polarization (DNP) are rapidly reshaping the research landscape and expanding the field of nuclear magnetic resonance (NMR) spectroscopy as a tool for solving complex chemical and structural problems. The past decade has seen considerable advances in this burgeoning method, while efforts to further improve its capabilities continue along many avenues. In this report, we examine the influence of static magnetic field strength and temperature on the reported 1H DNP enhancements from three conventional organic biradicals: TOTAPOL, AMUPol, and SPIROPOL. In contrast to the conventional wisdom, our findings show that at liquid nitrogen temperatures and 700 MHz/460.5 GHz, these three bisnitroxides all provide similar 1H DNP enhancements, ε ≈ 60. Furthermore, we investigate the influence of temperature, microwave power, magnetic field strength, and protein sample deuteration on the NMR experimental results.

A thin metallo-dielectric stacked metamaterial as “add-on” for magnetic field enhancement in clinical MRI

Magnetic resonance imaging (MRI) is a widely used clinical diagnostic tool, which is based on the principle of nuclear magnetic resonance of hydrogen atoms in human body. The Larmor frequency of precession of the hydrogen atoms is determined by the strength of static magnetic field ( B0) of MRI. A higher B0 can directly improve signal-to-noise ratio (SNR) of MRI. However, this method involves expensive hardware installation, which could have adverse effects of tissue-heating and make MRI unsafe for patients with medical implants. Hence, efforts have been made to increase the SNR of MRI without increasing B0. An effective solution in this direction would be to boost the radiofrequency (RF) magnetic fields emitted by the body part undergoing scan, particularly by using metamaterials. The higher the received RF signal strength, the greater the SNR of MRI. For a metamaterial to be used as an “add-on” in commercial scanners, its dimensions need to be designed appropriately so that it fits in the available gap between the transceiver coil and the human body. In this article, a 10-mm-thick metallo-dielectric metamaterial is designed by a stacking of alternate square-shaped capacitive patches and inductive apertures for enhancing the RF magnetic flux density and hence, the SNR of a 1.5 T MRI system. The inter-layer electromagnetic coupling in the stacked structure is deployed for spatial localization of magnetic fields at the resonant frequency (∼64 MHz) which is equal to the Larmor frequency of 1.5 T MRI. An equivalent circuit model, comprising a lumped-element third order bandpass filter, validated the transmissivity characteristics of the metamaterial obtained using full-wave simulations. Magnetic flux density enhancement by a factor of 55 is obtained when the metamaterial add-on is placed between a surface coil and a bio-model of human head.

Health effects related to exposure of static magnetic fields and acoustic noise—comparison between MR and CT radiographers

ObjectivesWe explored the prevalence of health complaints subjectively associated with static magnetic field (SMF) and acoustic noise exposure among MR radiographers in Sweden, using CT radiographers as a control group. Additionally, we explored radiographers’ use of strategies to mitigate adverse health effects.MethodsA cross-sectional survey was sent to all hospitals with MR units in Sweden. MR and/or CT personnel reported prevalence and attribution of symptoms (vertigo/dizziness, nausea, metallic taste, illusion of movement, ringing sensations/tinnitus, headache, unusual drowsiness/tiredness, forgetfulness, difficulties concentrating, and difficulties sleeping) within the last year. We used logistic regression to test associations between sex, age, stress, SMF strength, working hours, and symptom prevalence. Data regarding hearing function, work-environmental noise, and strategies to mitigate adverse symptoms were also analysed.ResultsIn total, 529 out of 546 respondents from 86 hospitals were eligible for participation. A ≥ 20 working hours/week/modality cut-off rendered 342 participants grouped into CT (n = 75), MR (n = 121), or mixed personnel (n = 146). No significant differences in symptom prevalence were seen between groups. Working at ≥ 3T increased SMF-associated symptoms as compared with working at ≤ 1.5T (OR: 2.03, CI95: 1.05–3.93). Stress was a significant confounder. Work-related noise was rated as more troublesome by CT than MR personnel (p < 0.01). MR personnel tended to use more strategies to mitigate adverse symptoms.ConclusionNo significant differences in symptom prevalence were seen between MR and CT radiographers. However, working at 3T increased the risk of SMF symptoms, and stress increased adverse health effects. Noise nuisance was considered more problematic by CT than MR personnel.Key Points• No significant differences in symptom prevalence were seen between MR and CT radiographers.• Working at ≥ 3 T doubled the odds of experiencing SMF symptoms (vertigo/dizziness, nausea, metallic taste, and/or illusion of movement) as compared to working exclusively at ≤ 1.5 T.• Work-related acoustic noise was less well mitigated and was rated as more troublesome by CT personnel than by MR personnel.

Performance investigation on the balance of static and dynamic magnetic field strength of magnetostrictive patch transducer with different permanent magnets

Nowadays, a magnetostrictive patch transducer(MPT) utilizing the high magnetostriction patch such as iron-cobalt alloy attached to the tested specimen like pipes, tubes, and cables has attracted more attention from many scholars. A harmonized flexible printed coil magnetostrictive patch transducer (HFPC-MPT) was proposed in 2019 by the author's research group, and this high-performance MPT could generate a more even magnetostrictive force than before. However, that research was an MPT optimization from sensor circuit design perspective. From the perspective of the magnetic field, this type of sensor has not been explored yet to improve its performance. In this research, firstly, the author conducted numerical simulations to find the optimal balance range between the static and dynamic magnetic fields of HFPC-MPT. Secondly, some experiments have been designed to verify the simulation results. The simulation results have been validated and are in agreement with the experimental results. This research provided a deep insight into improving the performance of HFPC-MPT from the perspective of the static magnetic field, which is also beneficial to both industrial and academic areas.

Anomalous Electromagnetic Field Penetration in a Weyl or Dirac Semimetal.

The current response to an electromagnetic field in a Weyl or Dirac semimetal becomes nonlocal due to the chiral anomaly activated by an applied static magnetic field. The nonlocality develops under the conditions of the normal skin effect and is related to the valley charge imbalance generated by the joint effect of the electric field of the impinging wave and the static magnetic field. We elucidate the signatures of this nonlocality in the transmission of electromagnetic waves. The signatures include enhancement of the transmission amplitude and its specific dependence on the wave's frequency and the static magnetic field strength.

A New Design of the Dual-Mode and Pure Longitudinal EMAT by Using a Radial-Flux-Focusing Magnet.

An electromagnetic acoustic transducer (EMAT) is suitable for measuring the propagation time more accurately without causing abrasion to the transducer during testing due to the principle of its excitation. This work designs a flux-concentrating EMAT with a radial-flux-focusing permanent magnet to significantly enhance static magnetic field strength. Through theoretical analysis and finite element simulation, two kinds of coils are designed according to the concentration areas of the horizontal and vertical components of the magnetic field. One is used to generate pure longitudinal waves, and the other is used to generate both longitudinal waves and shear waves. The experimental comparison shows that the amplitudes of the pure longitudinal wave and the dual-mode wave excited by the two kinds of coils with the radial-flux-focusing magnet are more than two times higher than those with the ordinary magnet. Therefore, the flux-concentrating EMAT with the appropriate coil provides an insight into realizing more accurate detection where longitudinal wave detection is required.

Optimization of Inside-Out Nuclear Magnetic Resonance Sensor With Logging-While-Drilling Tool Specification and Experimental Validation

The sensor determines the basic performance of the nuclear magnetic resonance (NMR) logging-while-drilling (LWD) system. However, the electromagnetic calculation and structure optimization of the sensor are complicated and difficult. In this study, we proposed an effective design method for inside-out NMR LWD sensor from the perspective of electromagnetic filed. First, a region of interest (ROI) was set first, the static magnetic field strength range in ROI corresponding to the ideal operating frequency bandwidth was defined as sensitive region, and the magnet system was optimized efficiently by introducing uniform design method to maximize the sensitive region. Different simplified finite element models were established to calculate different electromagnetic parameters of the RF coil system. The inside-out NMR LWD sensor was processed. Static magnetic field measurement result show that the proposed static magnetic field optimization method can effectively obtain the sensitive region with ideal radial position and strength, and is superior to the traditional optimization method. The NMR signal detection ability was tested by importing the Carr–Purcell–Meiboom–Gill (CPMG) sequence and phase-alternate pulse sequence technology. In particular, a porous and radially layered measurement device was designed, the signal sensitive region was quantitatively measured based on changes in sample porosity, and the width and height of signal sensitive region are 50 mm and 90 mm, respectively. The differences between static magnetic field sensitive region and signal sensitive region were analyzed, and suggestions for improving the sensor optimization method were provided at last.

Yield strength measurement of ferromagnetic materials based on the inverse magnetostrictive effect

Ferromagnetic materials are widely used in industry and risking the hazards of aging and degradation of their mechanical properties. This paper proposed a non-destructive method for the measurement of the yield strength of ferromagnetic materials imprinted by the materials’ microstructure as the microstructure influences the pattern of the inverse magnetostrictive effect of ferromagnetic materials. For experimental verification, yield strengths of ferromagnetic specimens were measured on an electromagnetic ultrasonic transducer (EMAT) detection system. The relationship between electromagnetic acoustic transducer signals and the static magnetic field strength was obtained, from which we extracted the pattern parameters related to the yield strength. The regression model of the pattern parameters versus the yield strength was established and then verified with trial on a specimen processed in the same batch with a maximum prediction accuracy of 12.78%.

Effect of magnetic field‐assisted freezing on water migration, fractal dimension, texture, and other quality changes in tilapia

To study the effect of magnetic field-assisted freezing on tilapia quality changes, this experiment used the application of a magnetic field as an auxiliary condition to freeze tilapia, and the static magnetic field strength was 0 G, 5 G, 10 G, 15 G, 20 G, 30 G. The results show that magnetic field-assisted freezing has a positive effect on the freezing rate, water migration, microstructure, and other aspects. Among the strengths applied, the effect of 15 G is the most significant, and the effect of 20 G and 30 G is lower than that of 15 G. Compared with the control group, the magnetic field intensity of the other groups showed no significant difference in the effect of each index. Under the experimental conditions, the magnetic field has a significant promotion effect on the sample quality, but the effect does not increase linearly with the increase of the magnetic field intensity. Novelty impact statement The use of magnetic field for auxiliary freezing provides a new theoretical method for the freezing quality of tilapia. Using fractal dimension to quantitatively analyze the quality of frozen tilapia and verify the applicability of magnetic field in frozen tilapia.

7 Tesla and Beyond: Advanced Methods and Clinical Applications in Magnetic Resonance Imaging.

Ultrahigh magnetic fields offer significantly higher signal-to-noise ratio, and several magnetic resonance applications additionally benefit from a higher contrast-to-noise ratio, with static magnetic field strengths of B0 ≥ 7 T currently being referred to as ultrahigh fields (UHFs). The advantages of UHF can be used to resolve structures more precisely or to visualize physiological/pathophysiological effects that would be difficult or even impossible to detect at lower field strengths. However, with these advantages also come challenges, such as inhomogeneities applying standard radiofrequency excitation techniques, higher energy deposition in the human body, and enhanced B0 field inhomogeneities. The advantages but also the challenges of UHF as well as promising advanced methodological developments and clinical applications that particularly benefit from UHF are discussed in this review article.