Static Magnetic Field Research Articles

Simultaneously measuring microwave electric fields at different frequencies by Rydberg-atom-based electrometry with Zeeman-resolved Autler–Townes splitting

We provide the simultaneous traceable measurements of microwave electric fields at two different frequencies by the electromagnetically induced transparency (EIT) and Autler–Townes (AT) splitting. A static magnetic field working together with a linearly polarized probe and coupling light prepares Rydberg atoms in Zeeman sublevels with maximal |mJ| in an atomic vapor cell. Using the EIT-AT splitting of these two maximal |mJ| states, the microwave electric fields at two different frequencies are simultaneously measured, in which their frequency difference can be adjustable within the linear range of magnetic field-induced level shifts. The proposed method provides a promising prospect for calibrating multiple microwave frequencies simultaneously in the future.

Impact of the Out‐Of‐Plane Flow Shear on Magnetic Reconnection at the Flanks of Earth's Magnetopause

AbstractMagnetic reconnection changes the magnetic field topology and facilitates the energy and particle exchange at magnetospheric boundaries such as the Earth's magnetopause. The flow shear perpendicular to the reconnecting plane prevails at the flank magnetopause under southward interplanetary magnetic field conditions. However, the effect of the out‐of‐plane flow shear on asymmetric reconnection is an open question. In this study, we utilize kinetic simulations to investigate the impact of the out‐of‐plane flow shear on asymmetric reconnection. By systematically varying the flow shear strength, we analyze the flow shear effects on the reconnection rate, the diffusion region structure, and the energy conversion rate. We find that the reconnection rate increases with the upstream out‐of‐plane flow shear, and for the same upstream conditions, it is higher at the dusk side than at the dawn side. The diffusion region is squeezed in the outflow direction due to magnetic pressure which is proportional to the square of the Alfvén Mach number of the shear flow. The out‐of‐plane flow shear increases the energy conversion rate , and for the same upstream conditions, the magnitude of is larger at the dusk side than at the dawn side. This study reveals that out‐of‐plane flow shear not only enhances the reconnection rate but also significantly boosts energy conversion, with more pronounced effects on the dusk‐side flank than on the dawn‐side flank. These insights pave the way for better understanding the solar wind‐magnetosphere interactions.

Performance enhancement of frequency-doubling gyroklystron amplifier by magnetic field tapering

A uniform magnetic field across the device is often used to analyze gyroklystron. In this paper, a tapered magnetic field is applied across the two-cavity 35 GHz frequency-doubling gyroklystron to improve its performance. Device performance is compared between tapered and uniform magnetic field cases using particle-in-cell code “CST.” The result confirms that the tapered magnetic field significantly improves the device performance parameters such as output power, efficiency, gain, and bandwidth compared to uniform magnetic field conditions. With a 1.6-kW driver power, 306 kW RF output power along with 22.8 dB gain is achieved for a tapered magnetic field case, while 227 kW RF output power along with 21.5 dB gain is achieved for a uniform magnetic field case. When the magnetic field is uniform, the efficiency and bandwidth of a gyroklystron are approximately 21.6% and 100 MHz, respectively; however, for the tapered magnetic field, it can rise to 29.1% and 120 MHz, respectively. Device efficiency results suggest that a tapered magnetic field improves energy transfer from the electron beam to the RF field. A parametric study for both magnetic field cases examines the effect of magnetic field strength, beam current, beam voltage, and pitch factor on the device. This detailed research recommends optimizing frequency-doubling gyroklystron performance with tapered magnetic fields.

Static Magnetic Field Focusing With Neodymium Magnets For Wound Healing: A Numerical Study

Static magnetic fields (SMFs) find widespread applications in diverse scientific, technological, and medical domains. This study explores the potential of neodymium permanent magnets in focusing and controlling SMFs, specifically emphasizing wound healing applications. Numerical simulations using COMSOL Multiphysics create a uniform static magnetic field for wound healing. The study systematically increases the number of neodymium magnets, demonstrating enhanced magnetic flux density and a focused magnetic field. The results affirm the efficacy of neodymium magnets in generating a uniform static magnetic field between 160-600 m Tesla. This research proposes neodymium permanent magnets as a promising tool for wound healing applications, offering a non-invasive and focused therapeutic approach. While the study provides valuable insights, further experimental and clinical validations are necessary to establish the real-world efficacy of this method. The work contributes to the evolving understanding of static magnetic fields as a viable therapeutic modality for various medical conditions, particularly in the context of wound healing.

A new theoretical model for high-order harmonics of SH0 mode ultrasonic guided waves based on magnetostrictive mechanism

In recent years, it was found that magnetostrictive ultrasonic guided wave transducers experimentally excited nonlinear harmonic components under a certain combination of dynamic and static magnetic fields. However, a satisfactory model for the relevant excitation mechanisms is not available. In this study, a new magnetostrictive guided wave excitation model was established and the causes for harmonics generation were analyzed. In addition, the calculation results of the model were obtained under different magnetic field parameters. We firstly changed the calculation conditions of magnetostrictive strain in the model and then theoretically calculated the odd and even harmonics of SH0 mode ultrasonic guided waves for the first time. Furthermore, the accuracy of the model was experimentally verified. By changing the strength ratio of the dynamic magnetic field to the static magnetic field (HD/HS), the excitation amplitudes of odd and even harmonics could be regulated with a magnetostrictive sensor. As the ratio of HD/HS increased, the normalized amplitude of the second harmonic firstly increased and then decreased, whereas the normalized amplitude of the third harmonic showed an exponential growth with different curvatures. This study enriched the theory of magnetostrictive guided wave excitation and provided a theoretical basis for the applications of magnetostrictive sensors.

Preparation of Cu nanolayers by magnetic field-assisted electrodeposition and research on the nucleation and growth mechanism

Electrodeposition technology is widely used in the surface treatment of copper foil, and the core of this technology is roughening and curing treatment. During the electrodeposition process, the deposited layers often exhibits some problems, such as coarse grain size, uneven thickness and difficult control of crystal morphology. The magnetohydrodynamic (MHD) effect of magnetic field can obviously control the electrodeposition of Cu and improve the micro-morphology and performance of deposited layers. In this paper, Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV) and Chronocoulometry (CC) curves were adopted to investigate the electrochemical behavior of deposited Cu in ultra-high acidity sulfate systems under different magnetic field conditions. The nucleation and growth mechanism were discussed, and the micro-morphology of deposited layers was analyzed. The results show that the electrodeposition of Cu follows the three-dimensional (3D) growth mechanism of progressive nucleation and diffusion control under the static condition, and the deposits appear cylindrical shape formed by spherical agglomerated. The magnetic field significantly improves the mass transfer rate, and the deposited layers will be more uniform and dense, following 3D growth mechanism under the electrochemical control. With the increasing of magnetic field intensity, the nucleation mechanism gradually shifts from progressive to transient nucleation. At the early stage of nucleation, the high-intensity magnetic field can significantly increase the number of grains and refine them, obtaining uniform and dense deposited nanolayers.

An "All-in-One" Strategy to Reconstruct Temporomandibular Joint Osteoarthritic Microenvironment Using γ-Fe2O3@TA@ALN Nanoparticles.

Current clinical strategies for the treatment of temporomandibular joint osteoarthritis (TMJOA) primarily target cartilage biology, overlooking the synergetic effect of various cells and inorganic components in shaping the arthritic microenvironment, thereby impeding the effectiveness of existing therapeutic options for TMJOA. Here, γ-Fe2O3@TA@ALN magnetic nanoparticles (γ-Fe2O3@TA@ALN MNPs) composed of γ-Fe2O3, tannic acid (TA), and alendronate sodium (ALN) are engineered to reconstruct the osteoarthritic microenvironment and mitigate TMJOA progression. γ-Fe2O3@TA@ALN MNPs can promote chondrocytes' proliferation, facilitate chondrogenesis and anisotropic organization, enhance lubrication and reduce cartilage wear, and encourage cell movement. Magnetic-responsive γ-Fe2O3@TA@ALN MNPs also exhibit pH sensitivity, which undergoes decomposition within acidic environment to release ALN on demand. Under a 0.2 T static magnetic field, γ-Fe2O3@TA@ALN MNPs accelerate the synthesis of cartilage-specific proteins, and suppress catabolic-related genes expression and reactive oxygen species generation, affording additional protection to TMJ cartilage. In TMJOA mouse models, articular injection of γ-Fe2O3@TA@ALN MNPs effectively alleviates cartilage degeneration and subchondral bone loss in short and long terms, offering promising avenues for the development of therapeutic interventions for TMJOA.

Single and double quantum transitions in spin-mixed states under photo-excitation

Electronic spins associated with the Nitrogen-Vacancy (NV) center in diamond offer an opportunity to study spin-related phenomena with extremely high sensitivity owing to their high degree of optical polarization. Here, we study both single- and double-quantum transitions (SQT and DQT) in NV centers between spin-mixed states, which arise from magnetic fields that are non-collinear to the NV axis. We demonstrate the amplification of the ESR signal from both these types of transition under laser illumination. We obtain hyperfine-resolved X-band ESR signal as a function of both excitation laser power and misalignment of static magnetic field with the NV axis. This, combined with our analysis using a seven-level model that incorporates thermal polarization and double quantum relaxation, allows us to comprehensively analyze the polarization of NV spins under off-axis fields. Such detailed understanding of spin-mixed states in NV centers under photo-excitation can help greatly in realizing NV-diamond platform’s potential in sensing correlated magnets and biological samples, as well as other emerging applications, such as masing and nuclear hyperpolarization.

Spin-torque vortex-oscillator with modified saturation magnetization in ferromagnetic nanodots

Recent years have seen greater interest in manipulating vortex states in magnetic nanostructures for non-volatile memory and logic networks. We show how reducing saturation magnetization locally in ferromagnetic thick nanodot vortex-based spin-torque nano-oscillators modulates their frequency using micromagnetic simulations. When a spin-polarized current and a static in-plane magnetic field are applied to the vortex core of an isolated thick nanodot, the uniform gyrotropic modes and the first higher-order gyrotropic mode resonate at different frequencies in various saturation magnetization areas. The intensity of the first higher-order mode gets almost suppressed in areas with modified saturation magnetization. With linewidths ranging from 25 to 70 MHz with the considered dimensions, these small spin-torque vortex-oscillator devices made of thick Permalloy nanodots seem promising for use in gigahertz signal processing. Our study suggests that locally modifying saturation magnetization may be a cost-effective technique to build dense oscillator and array networks for neuromorphic computing without lithographical fabrication stages.

TMS-EEG signatures of the effects of transcranial static magnetic field stimulation (tSMS) on cortical excitability

In transcranial static magnetic field stimulation (tSMS), a strong and small magnet placed over the head can modulate cortical functions below the magnet as well as those in the region remote from the magnet. We studied the neuromodulation induced by tSMS using transcranial magnetic stimulation (TMS) combined with simultaneous electroencephalography (EEG) to clarify the neurophysiological underpinnings of tSMS. tSMS or sham stimulation was applied over the left primary motor cortex (M1) for 20 min in 15 healthy subjects. Single pulse TMS was delivered over the left M1 before and after the intervention, while recording EEG. The amplitude around the P30 of the TMS-evoked potentials (TEPs) in the left primary sensorimotor area (SM1) significantly decreased after the real tSMS, and that around the N60 of the TEPs in the right SM1 significantly increased after the real tSMS. In addition, the alpha power of the TMS-induced oscillatory responses (IORs) in the left and right SM1 significantly decreased after the real tSMS. TMS-EEG is a powerful tool for studying local and global cortical reactivity to external stimuli at high temporal resolution. tSMS altered TEPs and IORs both at the stimulated cortex and at the contralateral cortex. These findings would be related to the neurophysiological mechanisms underlying the neuromodulation induced by tSMS.

Static magnetic field contributes to osteogenic differentiation of hPDLSCs through the H19/Wnt/β-catenin axis

BackgroundStatic magnetic field (SMF) as an effective physical stimulus is capable of osteogenic differentiation for multiple mesenchymal stem cells, including human periodontal ligament stem cells (hPDLSCs). However, the exact molecular mechanism is still unknown. Therefore, this study intends to excavate molecular mechanisms related to SMF in hPDLSCs using functional experiments. MethodshPDLSCs were treated with different intensities of SMF, H19 lentivirus, and Wnt/β-catenin pathway inhibitor (XAV939). Changes in osteogenic markers (Runx2, Col Ⅰ, and BMP2), Wnt/β-catenin markers (β-catenin and GSK-3β), and calcified nodules were examined using RT-qPCR, western blotting, and alizarin red staining in hPDLSCs. ResultsSMF upregulated the expression of H19, and SMF and overexpressing H19 facilitated the expression of osteogenic markers (Runx2, Col Ⅰ, and BMP2), activation of the Wnt/β-catenin pathway, and mineralized sediment in hPDLSCs. Knockdown of H19 alleviated SMF function, and treatment with XAV939 limited SMF- and H19-mediated osteogenic differentiation of hPDLSCs. Notably, the expression of hsa-miR-532-3p, hsa-miR-370-3p, hsa-miR-18a-5p, and hsa-miR-483-3p in hPDLSCs was regulated by SMF, and may form an endogenous competitive RNA mechanism with H19 and β-catenin. ConclusionSMF contributes to the osteogenic differentiation of hPDLSCs by mediating the H19/Wnt/β-catenin pathway, and hsa-miR-532-3p, hsa-miR-370-3p, hsa-miR-18a-5p, and hsa-miR-483-3p may be the key factors in it.

Excitation of electrostatic lower hybrid wave by nonlinear interaction of hermite cosh-gaussian and cosh-gaussian laser beams in collisional plasma embedded with static magnetic field

Excitation of electrostatic lower hybrid wave by nonlinear interaction of hermite cosh-gaussian and cosh-gaussian laser beams in collisional plasma embedded with static magnetic field

The dissolution of metal carbonate precipitation under the external electric and magnetic fields: reactive force field molecular dynamics simulation

Abstract The dissolution of metal carbonates holds a pivotal role in diverse industrial processes, environmental occurrences, and geological formations. Grasping the fundamental mechanisms underlying these processes is imperative for enhancing industrial applications and mitigating environmental impacts. Herein, we undertake a thorough investigation employing reactive forcefieldmolecular dynamics simulations to delve into the dissolution process of metal carbonates. These simulations afford profound insights into the mechanisms and kinetics governing the process across various conditions, encompassing temperature, acidity, and external electric and magnetic fields. Although temperature itself exerts a limited influence, the study reveals a synergistic enhancement of metal carbonate dissolution kinetics when temperature is combined with static electric and magnetic fields. Our revelations offer enlightening perspectives on the intricate interplay of factors shaping dissolution processes, laying the foundation for future inquiries in this domain.

Formation of quasi unipolar pulses in nonequilibrium magnetized plasma channels

The possibility of controlling both the spectral and polarization properties of THz pulses propagating in strongly nonequilibrium extended magnetized plasma channels formed by intense UV femtosecond laser pulses in nitrogen (air) is analyzed. The formation of quasiunipolar pulses with a nonzero electric area and a specific state of polarization is discussed. The transformation of such pulses upon leaving the region of a static magnetic field is analyzed.

Low-intensity magnetization pretreatment to enhance biomethane generation and the abundance of key microorganisms for anaerobic digestion of sewage sludge

This work explores the impact of static magnetic field (SMF) intensity on biomethane production from anaerobic digestion (AD) of sewage sludge. Two different SMF intensities (20 mT and 1.5 T) were applied to magnetize the sludge destined to the AD process. The magnetic pretreatment at 20 mT was particularly effective, as it increased biomethane production by 12.7 % compared to the control test. On the contrary, exposing the sludge to 1.5 T adversely affected biomethane production, resulting in a 15.1 % decrease. The positive correlation observed between low-intensity SMF exposure and enhanced biomethane yield, in contrast to the inhibitory effect of high-intensity SMF, suggests the existence of an optimal intensity threshold within the lower range for maximizing methane production. The impact of magnetic pretreatment on the anaerobic microbial community was investigated through high-throughput sequencing analysis of magnetized sludge samples. This approach enabled the identification of specific shifts in microbial populations associated with SMF exposure, thereby elucidating the role of SMF in modulating key microbial communities for the AD process. The findings of this study provide insights into the potential mechanisms underlying these responses and underscore the potential of SMF application for improving the anaerobic valorization of sewage sludge.

Effect of magnetic anisotropy and interaction on spatial focused hyperthermia for rotating and oscillating fields

The behavior of magnetic nanoparticles in a time-varying magnetic field has several practical applications. One of these is hyperthermia used in the treatment of cancer. The nanoparticles injected in the tumor cells release the energy absorbed from the time dependent external magnetic field in the form of heat to its environment in a well-localized way. The aim of the research in this area is to maximize the amount of the dissipated energy. Using a combination of an oscillating and static magnetic field, this dissipated energy can be more focused in space. In this article, we investigated whether this spatial focusing is also present using a rotating and static field together. Furthermore, we investigated the effects of anisotropy and interaction between nanoparticles on this spatial focusing effect using the jump-diffusion model for Néel relaxation in both cases. This kinetic Monte Carlo (MC) method was validated and compared with the stochastic Landau-Lifshitz-Gilbert (SLLG) equation based model. We have shown that the spatial focusing effect is also present for these non-idealized experimentally realizable cases. Also, the effect of rotating magnetic field on magnetic nanoparticles was not investigated in kinetic Monte Carlo simulations before.

Additively manufactured 17–4 PH stainless steels for fracture management devices

ABSTRACT Stainless steel 316L (SS316L) is widely used in fracture management devices. However, SS316L does not offer any bacterial infection resistance and can cause metal-ion sensitivity due to Ni-ions’ presence. 17-4PH can emerge as a promising substitute due to the intrinsic antibacterial properties of copper, a 75% reduction in nickel content, and superior mechanical properties. SS316L and 17–4 PH were manufactured using laser-directed energy deposition (LDED). 17-4PH specimens surpassed the compressive strength of SS316L by over 150%. A static magnetic field was generated in 17–4 PH specimens to understand in vitro bone cell–material interactions. In vitro human fetal osteoblast cell culture and bacterial inhibition study using Staphylococcus aureus and Pseudomonas aeruginosa were carried out on these specimens with SS316L as control and as-processed and magnetised 17–4 PH as treatments. Results demonstrated that magnetised 17–4 PH exhibited 25% enhancement in hFOB proliferation and 70% reduction in bacterial colonisation compared to SS316L.

Quality Enhancement of Shrimp Surimi by Static Magnetic Field Treatment at 4 ºC

Quality Enhancement of Shrimp Surimi by Static Magnetic Field Treatment at 4 ºC

Thermal performance of nanofluid natural convection magneto-hydrodynamics within a chamber equipped with a hot block

In this study, flow and free convection thermal performance within a chamber in the presence of a permanent magnetic field are simulated. Boussinesq approximation and the Lorentz force equation are used for the density variation in free convection, and the magnetic field, respectively. The steady-state, two-dimensional, and incompressible governing equations are simulated using the Semi-Implicit Method for Pressure Linked Equations (SIMPLE). The present study is simulated for different Rayleigh numbers (Ra) corresponding to the situation where the conduction mechanism was predominant (Ra = 100) and the convection heat transfer was predominant (Ra = 105). Also, different intensities of the magnetic field (0 ≤ Ha ≤ 40) and different directions of the magnetic field along with the effects of three different nanoparticles Ag, Cu, and Al2O3 are given. The present study showed that in the case of the dominant convection mechanism, the presence of the magnetohydrodynamics (MHD) condition decreases the Nusselt number (Nu). However, if the conduction is predominant, the applied magnetic field improves the average Nu number. The optimum state for the magnetic field strength was found in the low Rayleigh number. The presence of nanoparticles also intensifies the magnetic field effects. In the high Rayleigh number, the heat transfer rate reduces by 13.5% with the increase of the Hartmann number.

Static magnetic field effects on the secondary structure and elasticity of collagen molecules; a possible biophysical approach to treat keratoconus

Type I collagen is among the major extracellular proteins that play a significant role in the maintenance of the cornea's structural integrity and is essential in cell adhesion, differentiation, growth, and integrity. Here, we investigated the effect of 300 mT Static Magnetic Field (300 mT SMF) on the structure and molecular properties of acid-solubilized collagens (ASC) isolated from the rat tail tendon. The SMF effects at molecular and atomic levels were investigated by various biophysical approaches like Circular Dichroism Spectropolarimetery (CD), Fourier Transform Infrared Spectroscopy (FTIR), Zetasizer light Scattering, and Rheological assay. Exposure of isolated type I collagen to 300 mT SMF retained its triple helix. The elasticity of collagen molecules and the keratoconus (KCN) cornea treated with SMF decreased significantly after 5 min and slightly after 10, 15, and 20 min of treatments. The exposure to 300 mT SMF shifted the Amid I bond random coil to antiparallel wave number from 1647 to 1631 cm−1. The pH of the 300 mT SMF treated collagen solution increased by about 25 %. The treatment of the KCN corneas with 300 mT SMF decreased their elasticity significantly. The promising results of the effects of 300 mT SMF on the collagen molecules and KCN cornea propose a novel biophysical approach capable of manipulating the collagen's elasticity, surface charges, electrostatic interactions, cross binding, network formation and fine structure. Therefore, SMF treatment may be considered as a novel non-invasive, direct, non-chemical and fast therapeutic and manipulative means to treat KCN cornea where the deviated physico-chemical status of collagen molecules cause deformation.