Time-varying Magnetic Field Research Articles

Is activation of the vestibular system by electromagnetic induction a possibility in an MRI context?

In recent years, an increasing number of studies have discussed the mechanisms of vestibular activation in strong magnetic field settings such as occur in a magnetic resonance imaging scanner environment. Amid the different hypotheses, the Lorentz force explanation currently stands out as the most plausible mechanism, as evidenced by activation of the vestibulo-ocular reflex. Other hypotheses have largely been discarded. Nonetheless, both human data and computational modeling suggest that electromagnetic induction could be a valid mechanism which may coexist alongside the Lorentz force. To further investigate the induction hypothesis, we provide, herein, a first of its kind dosimetric analysis to estimate the induced electric fields at the vestibular system and compare them with what galvanic vestibular stimulation would generate. We found that electric fields strengths from induction match galvanic vestibular stimulation strengths generating vestibular responses. This review examines the evidence in support of electromagnetic induction of vestibular responses, and whether movement-induced time-varying magnetic fields should be further considered and investigated.

Role of Time-Varying Magnetic Field on QGP Equation of State

The phase diagram of quantum chromodynamics (QCD) and its associated thermodynamic properties of quark-gluon plasma (QGP) are studied in the presence of time-dependent magnetic field. The study plays a pivotal role in the field of cosmology, astrophysics, and heavy-ion collisions. In order to explore the structure of quark-gluon plasma to deal with the dynamics of quarks and gluons, we investigate the equation of state (EoS) not only in the environment of static magnetic field but also in the presence of time-varying magnetic fields. So, for determining the equation of state of QGP at nonzero magnetic fields, we revisited our earlier model where the effect of time-varying magnetic field was not taken into consideration. Using the phenomenological model, some appealing features are noticed depending upon the three different scales: effective mass of quark, temperature, and time-independent and time-dependent magnetic fields. Earlier the effective mass of quark was incorporated in our calculations, and in the current work, it is modified for static and time-varying magnetic fields. Thermodynamic observables including pressure, energy density, and entropy are calculated for a wide range of temperature- and time-dependent as well as time-independent magnetic fields. Finally, we claim that the EoS are highly affected in the presence of a magnetic field. Our results are notable compared to other approaches and found to be advantageous for the measurement of QGP equation of state. These crucial findings with and without time-varying magnetic field could have phenomenological implications in various sectors of high-energy physics.

Underwater target correlation detection and location method based on normalized magnetic moment

For the dynamic magnetic detection platform represented by airborne magnetic anomaly detection, the magnetic field measured by the vector magnetometer is easily affected by the rapid attitude change. Therefore, traditional anti-submarine aircraft are equipped with scalar magnetometers that are less affected by changes in the carrier attitude. However, the scalar magnetometer can only measure the total magnetic field signal, and its measurement information is single. It contains a time-varying environmental magnetic field signal, including the geomagnetic field, which is difficult to effectively reject. This brings great difficulties to the single real-time location of a magnetic anomaly target. This paper proposes a target correlation detection method based on the normalized magnetic moment that can effectively solve the above problems, considering the rotational invariance of magnetic anomaly measurements for dynamic magnetic exploration platforms and the efficient detection methods required for the single real-time positioning of targets. Correlation detection based on the normalized magnetic moment characteristic function and characteristic time search based on the correlation detection are included. Simulation and experimental results verify the single-point real-time positioning ability of the improved detection method within an effective operating distance. This method has strong usability for actual magnetic anomaly detection of underwater targets.

Broadband stripline Lenz lens achieves 11 × NMR signal enhancement

A Lenz lens is an electrically passive conductive element that, when placed in a time-varying magnetic field, acts as a magnetic flux concentrator or a magnetic lens. In the realm of nuclear magnetic resonance (NMR), Lenz lenses have been exploited as electrically passive metallic radiofrequency interposers placed between a sample and a tuned or untuned NMR detector in order to focus the B1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${B}_1$$\\end{document}-field of the detector onto a smaller sample space. Here we explore a novel embodiment of the Lenz lens, which acts as a non-resonant stripline interposer, i.e., the B1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${B}_1$$\\end{document}-field acts along the longitudinal volume of a sample container, such as a capillary or other microfluidic channel that is coincident with the axis of the stripline. The almost vanishing self-resonance of the stripline Lenz lens, at frequencies relevant for NMR, leads to a desirable B1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${B}_1$$\\end{document}-field amplitude that is nearly perfectly uniform across the sample and hence lacking a characteristic sinusoidal modal shape. The action of Lenz’ law ensures that no stray B1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${B}_1$$\\end{document}-field is found outside of the stripline’s active volume. Because the stripline Lenz lens does not rely on its own geometry to achieve resonance, its frequency response is thus widely broadband for field enhancements up to a factor of 11, with only the external driving resonator properties governing the overall resonant behaviour. We explore the use of the stripline Lenz lens with a sub-nanolitre sample volume, readily detecting 4 isotopes with resonances ranging from 125.76 to 500 MHz. The concept holds potential for the NMR study of thin films, small biological samples, as well as the in situ study of battery materials.

Thermal conductivity of evolving quark-gluon plasma in the presence of a time-varying magnetic field

Thermal conductivity of evolving quark-gluon plasma in the presence of a time-varying magnetic field

Modulation of calcium signaling and metabolic pathways in endothelial cells with magnetic fields.

Calcium signaling plays a crucial role in various physiological processes, including muscle contraction, cell division, and neurotransmitter release. Dysregulation of calcium levels and signaling has been linked to a range of pathological conditions such as neurodegenerative disorders, cardiovascular disease, and cancer. Here, we propose a theoretical model that predicts the modulation of calcium ion channel activity and calcium signaling in the endothelium through the application of either a time-varying or static gradient magnetic field (MF). This modulation is achieved by exerting magnetic forces or torques on either biogenic or non-biogenic magnetic nanoparticles that are bound to endothelial cell membranes. Since calcium signaling in endothelial cells induces neuromodulation and influences blood flow control, treatment with a magnetic field shows promise for regulating neurovascular coupling and treating vascular dysfunctions associated with aging and neurodegenerative disorders. Furthermore, magnetic treatment can enable control over the decoding of Ca signals, ultimately impacting protein synthesis. The ability to modulate calcium wave frequencies using MFs and the MF-controlled decoding of Ca signaling present promising avenues for treating diseases characterized by calcium dysregulation.

Temperature Rise Mechanism of Pacemaker Induced by a Time-Varying Gradient Magnetic Field

Temperature Rise Mechanism of Pacemaker Induced by a Time-Varying Gradient Magnetic Field

A Non-Steady State NMR Effect Based Time-Varying Magnetic Field Measurement Method and Experimental Apparatus

A Non-Steady State NMR Effect Based Time-Varying Magnetic Field Measurement Method and Experimental Apparatus

Quantum Sensing of Fast Time-Varying Magnetic Field With Daubechies Wavelets

Quantum Sensing of Fast Time-Varying Magnetic Field With Daubechies Wavelets

Effect of music rhythm magnetic field on long-term potentiation of hippocampal Schaffer-CA1 synapse plasticity

Music and magnetic fields both play important regulatory roles in brain learning and memory. The present study aimed to investigate the effects of music rhythmic magnetic fields at different frequencies on long-term potentiation (LTP) in the Schaffer-CA1 region of the hippocampus, with the goal of elucidating the molecular mechanisms underlying the impact of music rhythmic magnetic fields on brain learning and memory. Three different frequency music tracks were selected, including soothing track 1: Courante from the Baroque Suite, medium-frequency track 2: saxophone version of Liang Zhu, and high-frequency track 3: Johann Pachelbel’s music track Canon (trumpet version). Using an external sound card, power amplifier, and homemade coils, a time-varying magnetic field with a 2-mT music rhythm was produced to assess the effects of this magnetic field on LTP in the Schaffer-CA1 synapses of isolated rat hippocampal brain slices. The experimental results demonstrated that as the music frequency increased, the enhancing effect of the music rhythmic magnetic field on hippocampal synaptic plasticity LTP gradually intensified. Thus, high-frequency music rhythmic magnetic fields may offer a more effective means of enhancing LTP.

System design study of a VLEO satellite platform using the IRS RF helicon-based plasma thruster

To achieve a feasible lifetime of several years, most satellites are deployed in orbits higher than 400 km. Drag of residual atmosphere causes a slow orbit decay, resulting in the deorbit of the spacecraft. However, e.g. optical instruments or communication devices would significantly benefit from lower altitudes in the range of 150–250 km. A solution to achieve this could be the application of atmosphere-breathing electric propulsion (ABEP), where the residual atmosphere is used to generate continuous thrust that compensates the drag.Within the EU-funded DISCOVERER project, the Institute of Space Systems (IRS) developed an electrode-less RF Helicon-based Plasma Thruster (IPT) suitable for such applications. Ignition and preliminary discharge characterizations of the IPT have been carried out at IRS facilities, using argon, nitrogen and oxygen. To further characterize the plasma plume, a torsional pendulum has been designed to determine the (local) momentum flux in the plasma jet, as well as a three-axis magnetic B-dot probe to carry out time-varying magnetic field measurements. Various intake designs were investigated, opening the possibility to conduct studies on potential satellite platforms within the frame of the ESA-funded project RAM-CLEP.A design study for an Earth Observation and Telecommunication satellite operating at 150–250 km with an extended mission lifetime is currently being carried out. The first system assessment focused on the comparison of different spacecraft configurations (“slender body” and “flat body”) and intake designs (specular or diffuse) with regard to overall drag and ABEP performance requirements.In this contribution, the design approaches for the current thruster and the diagnostic methods are depicted. Moreover, the current status of the system assessment is presented. Upcoming experimental studies of the ABEP system e.g. within the ESA-project RAM-CLEP and additional activities planned on system assessment are outlined.

A comparison of magneto-responsive particles and testing protocols for active rheology control of cementitious materials

Magneto-responsive cementitious materials with magnetic interventions enable on-demand and real-time adjustment of rheology. This research aims to elaborate the early-stage magneto response of cement pastes using different types of Fe3O4 particles and carbonyl iron particles. A series of methods to evaluate the magnetorheological response of cementitious materials were established. The magneto-responsive cement pastes were tested by shear test and small amplitude oscillatory shear test at constant and time-varying magnetic fields. The increase of static yield stress and storage modulus after applying a magnetic field was a time-dependent process, while the decrease of static yield stress and storage modulus was an instant process at the moment of removing magnetic fields. Such a procedure can be reversibly controlled in real time. The cement pastes containing different magneto-responsive particles showed significant difference in the onset of flow and structural build-up. With the intervention of a magnetic field, the static yield stress and storage modulus of mixtures with carbonyl iron particles were able to increase with one order of magnitude. Compared with the particle size distribution and particle morphology, the magnetic parameters of magneto-responsive particles dominated the magnetorheological properties of cementitious materials. Shear tests were found the most effective to evaluate the magneto response of cement pastes with the intervention of a magnetic field.

Effect of light ellipticity and polarization angle on the transient dynamics of the ground-state Hanle effect

We report theoretical investigations on the transient dynamics of the ground-state Hanle effect in the Voigt geometry, where a time-varying scanning magnetic field B (t) is applied perpendicular to the light propagation direction. Transient Hanle signals are calculated for different light polarizations using a theoretical model based on the density matrix approach. First, we study the ellipticity dependence of transient Hanle signals in two configurations in which the major axis of the light polarization ellipse () is aligned either perpendicular or parallel to the field B . For B , elliptical polarization of the light produces oscillations of frequencies 2ΩL(t) and ΩL(t) simultaneously, where ΩL(t) is the Larmor frequency of the corresponding field B (t). On the other hand, in the case of || B , only ΩL(t) oscillation is observed using elliptically polarized light. Second, we vary the tilt angle between the polarization vector of a linearly polarized light and the orientation of the field B and study its effect on the transient response of Hanle signals. Both the amplitude and the decay rate of the oscillations show a strong dependence on the light ellipticity and tilt angle of the polarization vector. In addition, the influence of the magnetic field sweep rate on the transient signals is demonstrated for given values of light ellipticity and polarization angle.

AusLAMP shines a light on space weather hazards in the Australian high-voltage power grid

A geomagnetic storm, also known as a geomagnetic disturbance (GMD), is a major disturbance of the Earth’s magnetic field caused by solar activity. A geomagnetic storm induces electric currents in the Earth that feed into power lines through substation neutral earthing, causing instabilities and even blackouts in electricity transmission systems. The intensity of geomagnetically induced currents (GICs) is closely associated with the electrical conductivity of the surrounding geology. In this paper, we analyse one of the most well-known geomagnetic storms, the 1989 “Québec storm” and 688 magnetotelluric (MT) survey sites from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) to gain insight into the space weather hazard posed for Australia's modern-day power grids. Transmission lines may exhibit local maxima at differing times depending on their spatial orientation and length with respect to the time-varying magnetic field. Localised peak voltages over 100 V can be observed on some individual lines. This assessment identifies the distribution of GICs in south-eastern Australia for the 1989 Québec storm and transmission lines that are more vulnerable to GICs. It is relevant to national strategies and risk assessment procedures to mitigate space weather hazards in the Australian high-voltage power grid and the design of a more resilient power transmission system. We also analyse the 2015 “St Patrick’s Day storm” to study under-estimation of the space weather hazard associated with the band-limited geomagnetic data and MT data sets. Key points The subsurface geology has a great influence on the intensity of geomagnetically induced electric fields, potentially causing up to three orders of magnitude difference between conductive basins and resistive cratonic regions in south-eastern Australia. Analysis using the 1989 “Québec geomagnetic storm” and AusLAMP magnetotelluric data shows the intensity of the geoelectric fields in south-eastern Australia could reach up to 5 [V/km]. Geomagnetically induced voltages in the Australian high-voltage power grid could be in excess of 100 V in some transmission lines for a geomagnetic storm with intensity comparable with the 1989 Québec geomagnetic storm.

Moment Propagation of the Plasma-Charge Model with a Time-Varying Magnetic Field

Moment Propagation of the Plasma-Charge Model with a Time-Varying Magnetic Field

Cell migration-inspired stochastic steering strategy of magnetic particles in vascular networks

One primary challenge of magnetic drug targeting is to achieve the efficient and accurate delivery of drug particles to the desired sites in complex physiological conditions. Though a majority of drugs are delivered through intravenous administration, until now, the kinematics and dynamics of drug particles influenced by the magnetic field, vascular topology, and blood flows are still less understood. In this work, a multi-physics dynamical model, which captures transient particle motions inside the vascular networks manipulated by the external magnetic field, is developed. Based on the model, we studied the transport efficiency of particles in the two-dimensional (2D), three-dimensional (3D) artificial, and in vivo-relevant vascular networks. It is found that particles that perform a random walk with correlated speed and persistence, recapitulating some characteristics of migratory motion of immune and metastasis cells, have the largest mean square displacements in various vascular network topologies. Next, we designed a stochastic magnetic steering strategy, using a time-varying gradient magnetic field, to manipulate particles to perform the cell migration-inspired random motions in the vasculature. The capability of the proposed steering strategy to improve the particle spreading speed and reduce the consumed magnetic energy has been demonstrated using our multi-physics numerical model. Furthermore, the influence of heterogeneous flows in the vascular networks on the particle steering efficiency was investigated. Overall, the numerical model and the proposed stochastic magnetic steering strategy can be used to assist the development of drug delivery systems for precise medicine research.

Propulsion and Control of Microrobot Using a Multi-Selective Wireless Power Transfer Coil

Microrobots have been actively studied in recent years due to their mobility and usability. It is important to receive electrical energy from outside through wireless power transfer system because active circuits such as sensors and microrod controller unit should be included and operating time should be sufficient to increase the usability of microrobot. In this research, we propose a multi-selective wireless power transfer coil and structure to maximize the usability of the microrobot that can receive electrical energy with wireless power transmission systems and can be propelled and rotated at the same time. The proposed multi-selective wireless power transfer coil system architecture is described with a theoretical explanation of the magnetic force acting on the microrobot. To verify the proposed model, it has been verified through simulation and experimental verification that the time-varying magnetic field generated from four transmitting coils is suitable for the propulsion, generating torque, and power transmission of microrobot. To validate the proposed system, a 3 mm-sized microrobot is used for experimentation. The experimental results show that the microrobot is able to freely move and rotated as intended by controlling the external incident magnetic field.

Sophisticated Magneto-Mechanical Actuation Promotes In Situ Stem Cell Assembly and Chondrogenesis for Treating Osteoarthritis.

Abnormal mechanical loading often leads to the progressive degradation of cartilage and causes osteoarthritis (OA). Although multiple mechanoresponsive strategies based on biomaterials have been designed to restore healthy cartilage microenvironments, methods to remotely control the on-demand mechanical forces for cartilage repair pose significant challenges. Here, a magneto-mechanically controlled mesenchymal stem cell (MSC) platform, based on the integration of intercellular mechanical communication and intracellular mechanosignaling processes, is developed for OA treatment. MSCs loaded with antioxidative melanin@Fe3O4 magnetic nanoparticles (Magcells) rapidly assemble into highly ordered cell clusters with enhanced cell-cell communication under a time-varying magnetic field, which enables long-term retention and differentiation of Magcells in the articular cavity. Subsequently, via mimicking the gait cycle, chondrogenesis can be further enhanced by the dynamic activation of mechanical signaling processes in Magcells. This sophisticated magneto-mechanical actuation strategy provides a paradigm for developing mechano-therapeutics to repair cartilage in OA treatment.

Phase synchronization under mixed synapse between two heterogeneous functional neurons

Nervous system contacts and regulates the various systems and organs of the body by encoding and transmitting information, so it becomes important to explore the synaptic connections between neurons. In this study, two functional neurons are obtained by embedding Josephson junction and memristor in the FHN neuron circuit, and then based on Helmholtz’s theorem their Hamilton energies are calculated and investigated when coupled channel is awakened. There are weak but stable and orderly electromagnetic fields around human tissues and organs due to the transmembrane flow of ions, and their equilibrium state is easily disturbed and destroyed by the external electromagnetic fields, which should be considered when neuron model are investigated. Thus, an induction coil and a charge-controlled memristor (CCM) are used to perceive magnetic and electric fields respectively to couple the two function neurons, then mixed synapse is activated and synaptic plasticity is detect by parameter modulation and energy exchange. It is found that energy is continuously pumped along the coupling channel even if the synaptic connection is increased further, and two different functional neurons can only achieve quasi-phase synchronization or phase lock. However, the coupling strength threshold for achieving quasi-phase synchronization is lowered under hybrid synapses, and the possible mechanism may be that the addition of induction coil and CCM can induce time-varying electric and magnetic fields, which in turn facilitate the energy exchange in the coupled system. This study not only helps us to reveal the synchronization phenomenon of certain neurons observed in experiments, but also to explain the occurrence of pathological synchronization in the nervous system.

Numerical modelling of HTS tapes under arbitrary external field and transport current via integral method: review and application to electrical machines *

Superconductors in practical use can be subjected to spatially non-uniform and time-varying external magnetic field as well as carrying a transport current, for example, in an electrical machine. This paper verifies that the integral method can be used in situations in which the external field is spatially non-uniform, by providing both theoretical reasoning and simulation results. Variations in the integral method are reviewed, such as how to impose transport current. Further, the integral method is applied to calculate ac loss in superconducting tapes in an air-cored electrical machine in a two-stage process: the external field is calculated in a COMSOL model without superconducting tapes, and exported into the integral method model that consists of the tapes only. The time taken by the integral method is a small fraction of the time taken by the full machine model in COMSOL, which uses the T-A formulation. There are good agreements between the full COMSOL model and two-stage method incorporating the integral method.