Screening of magnetic fields by superconducting and hybrid shields with circular cross-section

The use of superconducting (SC) materials is crucial for shielding quasi-static magnetic fields. However, the frequent requisite of space-saving solutions with high shielding performance requires the development of a 3D modelling procedure capable of predicting the screening properties for different orientations of the applied field. In this paper, we exploited a 3D numerical model based on a vector potential formulation to investigate the shielding ability of SC screens with cylindrical symmetry and a height/diameter aspect ratio close to unity, without and with the superimposition of a ferromagnetic (FM) circular shell. The chosen materials were MgB2 and soft iron. First, the calculation outcomes were compared with the experimental data obtained on different shielding arrangements, achieving a notable agreement in both axial-field (AF) and transverse-field (TF) orientations. Then, we used the thus validated modelling approach to investigate how the magnetic mitigation properties of a cup-shaped SC bulk can be improved by the superimposition of a coaxial FM cup. Calculations highlighted that the FM addition is very efficient in enhancing the shielding factors (SFs) in the TF orientation. Assuming a working temperature of 30 K and using a layout with the FM cup protruding over the SC one, shielding factors up to 8 times greater than those of the single SC cup were attained at low applied fields, reaching values equal or higher than 102 in the inner half of the shield. In the AF orientation, the same FM cup addition costs a modest worsening at low fields, but at the same time, it widens the applied field range, where SF ≥ 104 occurs near the close extremity of the shield, up over 1 T.

Electromagnetic Exposure of Personnel Involved in Cardiac MRI Examinations in 1.5T, 3T and 7T Scanners

(1) Background: It has been hypothesised that a significant increase in the use of cardiac magnetic resonance (CMR), for example, when examining COVID-19 convalescents using magnetic resonance imaging (MRI), has an influence the exposure profiles of medical personnel to static magnetic fields (STmf). (2) Methods: Static exposure to STmf (SEmf) was recorded during activities that modelled performing CMR by radiographers. The motion-induced time variability of that exposure (TVEmf) was calculated from SEmf samples. The results were compared with: (i) labour law requirements; (ii) the distribution of vertigo perception probability near MRI magnets; and (iii) the exposure profile when actually performing a head MRI. (3) Results: The exposure profiles of personnel managing 42 CMR scans (modelled using medium (1.5T), high (3T) and ultrahigh (7T) field scanners) were significantly different than when managing a head MRI. The majority of SEmf and TVEmf samples (up to the 95th percentile) were at low vertigo perception probability (SEmf < 500 mT, TVEmf < 600 mT/s), but a small fraction were at medium/high levels; (4) Conclusion: Even under the “normal working conditions” defined for SEmf (STmf < 2T) by labour legislation (Directive 2013/35/EC), increased CMR usage increases vertigo-related hazards experienced by MRI personnel (a re-evaluation of electromagnetic safety hazards is suggested in the case of these or similar changes in work organisation).

Effect of High Static Magnetic Fields on Biological Activities and Iron Metabolism in MLO-Y4 Osteocyte-Like Cells

There are numerous studies that investigate the effects of static magnetic fields (SMFs) on osteoblasts and osteoclasts. However, although osteocytes are the most abundant cell type in bone tissue, there are few studies on the biological effects of osteocytes under magnetic fields. Iron is a necessary microelement that is involved in numerous life activities in cells. Studies have shown that high static magnetic fields (HiSMF) can regulate cellular iron metabolism. To illustrate the effect of HiSMF on activities of osteocytes, and whether iron is involved in this process, HiSMF of 16 tesla (T) was used, and the changes in cellular morphology, cytoskeleton, function-related protein expression, secretion of various cytokines, and iron metabolism in osteocytes under HiSMF were studied. In addition, the biological effects of HiSMF combined with iron preparation and iron chelator on osteocytes were also investigated. The results showed that HiSMF promoted cellular viability, decreased apoptosis, increased the fractal dimension of the cytoskeleton, altered the secretion of cytokines, and increased iron levels in osteocytes. Moreover, it was found that the biological effects of osteocytes under HiSMF are attenuated or enhanced by treatment with a certain concentration of iron. These data suggest that HiSMF-regulated cellular iron metabolism may be involved in altering the biological effects of osteocytes under HiSMF exposure.

A Magnetic Field Prevents Alcoholic Liver Disease by Reducing Oxidative Stress

The radical-pair recombination change will affect the generation of free radicals, which can be regulated by static magnetic fields (SMFs) in a SMF setting dependent way. It is well known that alcohol consumption leads to significantly increased free radical levels and health risks, which lacks effective treatment method besides alcohol abstinence. Here we compared different SMF settings and found that a downward SMF of ∼0.1 T with magnetic flux of ∼4.5×10−3 Wb could effectively alleviate alcohol-induced liver damage and lipid accumulation, and improve liver function. The inflammation, reactive oxygen species (ROS) level and oxidative stress were significantly reduced. EPR (electron paramagnetic resonance) experiments also confirmed the reduced amount of free radical by SMF treatment. Moreover, the lifespan of heavy alcohol drinking mice was also significantly changed due to the SMF effects on liver cell ROS level, DNA synthesis and liver cell regeneration. Our study shows that moderate SMFs with specific parameters have great promises to be developed into a physical method to reduce alcohol-induced liver damage in the future.

Magnetic field amplification driven by the gyro motion of charged particles

Spontaneous magnetic field generation plays important role in laser-plasma interactions. Strong quasi-static magnetic fields affect the thermal conductivity and the plasma dynamics, particularly in the case of ultra intense laser where the magnetic part of Lorentz force becomes as significant as the electric part. Kinetic simulations of giga-gauss magnetic field amplification via a laser irradiated microtube structure reveal the dynamics of charged particle implosions and the mechanism of magnetic field growth. A giga-gauss magnetic field is generated and amplified with the opposite polarity to the seed magnetic field. The spot size of the field is comparable to the laser wavelength, and the lifetime is hundreds of femtoseconds. An analytical model is presented to explain the underlying physics. This study should aid in designing future experiments.

Static Magnetic Fields Enhance the Chondrogenesis of Mandibular Bone Marrow Mesenchymal Stem Cells in Coculture Systems

Objectives. Combining the advantages of static magnetic fields (SMF) and coculture systems, we investigated the effect of moderate-intensity SMF on the chondrogenesis and proliferation of mandibular bone marrow mesenchymal stem cells (MBMSCs) in the MBMSC/mandibular condylar chondrocyte (MCC) coculture system. The main aim of the present study was to provide an experimental basis for obtaining better cartilage tissue engineering seed cells for the effective repair of condylar cartilage defects in clinical practice. Methods. MBMSCs and MCCs were isolated from SD (Sprague Dawley) rats. Flow cytometry, three-lineage differentiation, colony-forming assays, immunocytochemistry, and toluidine blue staining were used for the identification of MBMSCs and MCCs. MBMSCs and MCCs were seeded into the lower and upper Transwell chambers, respectively, at a ratio of 1 : 2, and exposed to a 280 mT SMF. MBMSCs were harvested after 3, 7, or 14 days for analysis. CCK-8 was used to detect cell proliferation, Alcian blue staining was utilized to evaluate glycosaminoglycan (GAG), and western blotting and real-time quantitative polymerase chain reaction (RT-qPCR) detected protein and gene expression levels of SOX9, Col2A1 (Collagen Type II Alpha 1), and Aggrecan (ACAN). Results. The proliferation of MBMSCs was significantly enhanced in the experimental group with MBMSCs cocultured with MCCs under SMF stimulation relative to controls ( P < 0.05 ). GAG content was increased, and SOX9, Col2A1, and ACAN were also increased at the mRNA and protein levels ( P < 0.05 ). Conclusions. Moderate-intensity SMF improved the chondrogenesis and proliferation of MBMSCs in the coculture system, and it might be a promising approach to repair condylar cartilage defects in the clinical setting.

Study of the effect of nitrogen and hydrogen on the structure and magnetic properties of (Sm, Er)2Fe17 alloys

Materials based on the Sm2Fe17 compound with nitrogen have great potential for the manufacture of highly efficient permanent magnets. The initial, nitrided, and hydrogenated alloys based on the Sm2Fe17 intermetallic compound with partial substitution of erbium atoms for samarium atoms Sm1.2Er0.8Fe17(H, N)x have been studied by X-ray phase analysis and scanning electron microscopy. Nanopowders of Sm1.2Er0.8Fe17N2 were obtained by mechanical grinding. The grinding time was varied from 0 to 60 minutes. The magnetic hysteresis properties of all powder samples were studied in static magnetic fields up to 7 T, as well as in pulsed magnetic fields up to 60 T. The strength of the intersublattice exchange interaction was estimated. The obtained values λ are valid only for the explored concentration of Sm/Er ions.