A Study of Differential Topology on the Magnetically Induced Isotropically Averaged Lorentz Force Density of a Few Simple Molecules.

Quantum chemical topology addresses the study of the chemical structure by applying the tools of differential topology to scalar and vector fields obtained by quantum mechanics. Here, the magnetically induced isotropically averaged Lorentz force density was computed and topologically analyzed for 11 small molecules. Critical points (attractors, repellers, and saddles) were determined and trajectories connecting the attractors computed. It is shown that kinds and numbers of the critical points are to some extent transferable in similar molecules. CC bonds of different orders are endowed with critical points of different kinds close to their center. The sum of topological indices of the isolated critical points is influenced by the presence of repellers on the outer part of the molecules.

Induced electric fields in MRI settings and electric vestibular stimulations: same vestibular effects?

In Magnetic Resonance Imaging scanner environments, the continuous Lorentz Force is a potent vestibular stimulation. It is nowadays so well known that it is now identified as Magnetic vestibular stimulation (MVS). Alongside MVS, some authors argue that through induced electric fields, electromagnetic induction could also trigger the vestibular system. Indeed, for decades, vestibular-specific electric stimulations (EVS) have been known to precisely impact all vestibular pathways. Here, we go through the literature, looking at potential time varying magnetic field induced vestibular outcomes in MRI settings and comparing them with EVS-known outcomes. To date, although theoretically induction could trigger vestibular responses the behavioral evidence remains poor. Finally, more vestibular-specific work is needed.

Gradient-induced vibrations and motion-induced Lenz effects on conductive nonmagnetic orthopedic implants in MRI.

PURPOSE: To quantify the extent of gradient-induced vibrations, and the magnitude of motion-induced displacement forces ("Lenz effect"), in conductive nonmagnetic orthopedic prostheses. METHODS: The investigation is carried out through numerical simulations, for a 3 T scanner. For gradient-induced torques and vibrations, a knee and a shoulder implant are considered, at dB/dt equal to 42 T/s (rms). For motion-induced forces associated with the Lenz effect, a knee and a hip implant are studied, considering a patient who translates on the examination couch, or walks next to it. RESULTS: Gradient-induced torques may be within the same order of magnitude as the worst case gravitational torque defined in the ASTM standards. However, for all investigated cases, they result to be lower. In vacuum, the extent of the corresponding vibration reduces with frequency. At the lowest investigated frequency (270 Hz), it keeps below 25 µm. For an implant partially embedded in bone, the extent of the vibration increases with frequency. Nevertheless, the displacement is far lower than the worst case observed in vacuum (negligible in contact with the bone; ˜1 µm or less where the implant emerges from the bone). The Lenz effect induced by the motion of the patient through the stationary magnetic field produces forces on the order of a few millinewtons (i.e., at least two orders of magnitude lower than the implant weight). CONCLUSION: Comparing the results with mechanical loads caused by ordinary activities of daily living, and with the levels of tolerable micromotions, a good safety margin is confirmed.

Lorentz Force-Actuated Bidirectional Nanoelectromechanical Switch with an Ultralow Operation Voltage.

The high operating voltage of conventional nanoelectromechanical switches, typically tens of volts, is much higher than the driving voltage of the complementary metal oxide semiconductor integrated circuit (∼1 V). Though the operating voltage can be reduced by adopting a narrow air gap, down to several nanometers, this leads to formidable manufacturing challenges and occasionally irreversible switch failures due to the surface adhesive force. Here, we demonstrate a new nanowire-morphed nanoelectromechanical (NW-NEM) switch structure with ultralow operation voltages. In contrast to conventional nanoelectromechanical switches actuated by unidirectional electrostatic attraction, the NW-NEM switch is bidirectionally driven by Lorentz force to allow the use of a large air gap for excellent electrical isolation, while achieving a record-low driving voltage of <0.2 V. Furthermore, the introduction of the Lorentz force allows the NW-NEM switch to effectively overcome the adhesion force to recover to the turn-off state.

Magnetically Responsive Gallium-Based Liquid Metal: Preparation, Property and Application.

Magnetically responsive soft smart materials have garnered significant academic attention due to their flexibility, remote controllability, and reconfigurability. However, traditional soft materials used in the construction of these magnetically responsive systems typically exhibit low density and poor thermal and electrical conductivities. These limitations result in suboptimal performance in applications such as medical radiography, high-performance electronic devices, and thermal management. To address these challenges, magnetically responsive gallium-based liquid metals have emerged as promising alternatives. In this review, we summarize the methodologies for achieving magnetically responsive liquid metals, including the integration of magnetic agents into the liquid metal matrix and the utilization of induced Lorentz forces. We then provide a comprehensive discussion of the key physicochemical properties of these materials and the factors influencing them. Additionally, we explore the advanced and potential applications of magnetically responsive liquid metals. Finally, we discuss the current challenges in this field and present an outlook on future developments and research directions.

Antisymmetric planar Hall effect in rutile oxide films induced by the Lorentz force.

The conventional Hall effect is linearly proportional to the field component or magnetization component perpendicular to a film. Despite the increasing theoretical proposals on the Hall effect to the in-plane field or magnetization in various special systems induced by the Berry curvature, such an unconventional Hall effect has only been experimentally reported in Weyl semimetals and in a heterodimensional superlattice. Here, we report an unambiguous experimental observation of the antisymmetric planar Hall effect (APHE) with respect to the in-plane magnetic field in centrosymmetric rutile RuO2 and IrO2 single-crystal films. The measured Hall resistivity is found to be linearly proportional to the component of the applied in-plane magnetic field along a particular crystal axis and to be independent of the current direction or temperature. Both the experimental observations and theoretical calculations confirm that the APHE in rutile oxide films is induced by the Lorentz force. Our findings can be generalized to ferromagnetic materials for the discovery of anomalous Hall effects and quantum anomalous Hall effects induced by in-plane magnetization. In addition to significantly expanding knowledge of the Hall effect, this work opens the door to explore new members in the Hall effect family.

Generation mechanism and empirical model of eddy current force and torque in drum-type eddy current separation.

Enhancing the recovery efficiency of non-ferrous metals in eddy current separation is of great significance. In this study, the accuracy of the simulation model was verified by comparing the eddy current force. The transformation mechanism of the Lorentz forces into the eddy current force and torque in non-ferrous metal particles was revealed by analyzing various physical fields. Then, the influence of magnetic field parameters on eddy current, eddy current force, and torque was studied. It shows that the eddy current force and torque are affected by the vector gradient of the magnetic field and the magnetic flux density, respectively. Additionally, the time derivative of the magnetic field impacts the magnitude of the eddy current force and torque by controlling the eddy current. On this basis, the empirical models of eddy current force and torque were established by similarity theory. The results obtained can improve and expand the application of eddy current separation.

Analysis and Compensation of Lorentz Force Magnetic Bearing Magnetic Flux Density Uniformity Error.

Aiming at the influence of the magnetic flux density uniformity error (MFDUE) of the Lorentz force magnetic bearing (LFMB) on the sensitivity accuracy of magnetically suspended control and sensing gyroscopes (MSCSGs) on the angular rate of a spacecraft, a high precision measurement method of the angular rate of a spacecraft based on the MFDUE compensation of LFMB is proposed. Firstly, the structure of MSCSG and the sensitivity principle of MSCSG to the spacecraft angular rate are introduced. The mechanism influencing the accuracy of MSCSG to spacecraft angular rate sensitivity is deduced based on the definition of magnetic flux density uniformity. Secondly, the 3D magnetic flux distribution of LFMB is analyzed using ANSYS. The relationship between the rotor tilt angle, tilt angular rate, and magnetic flux density is established. The induced current calculation model due to MFDUE is proposed, and the LFMB magnetic flux density error compensation is realized. Finally, the simulation results show that the estimation accuracy of the induced current by the proposed method can reach 96%, and the simulation and the experiment show that the error compensation method can improve the accuracy of MSCSG in measuring the spacecraft angular rate by 12.5%.

A Lorentz force-based SH-typed electromagnetic acoustic transducer using flexible circumferential printed circuit.

Structural health monitoring (SHM) of in-service structures is becoming increasingly important. The fundamental shear horizontal (SH0) guided wave mode in plate-like structures shows great potential in damage detection due to its non-dispersive and in-plane vibration properties. In order to generate SH0 waves, a practical Lorentz force-based electromagnetic acoustic transducer (EMAT) was introduced in this study using the flexible circumferential printed circuit (CPC). The designed principle of CPC-EMAT was similar to that of the circumferential magnet array (CMA)-based EMAT. However, the structure of the CMA-EMAT is complex, and it is difficult to assemble for generating high frequency and uniformly distributed omnidirectional SH0 waves. Firstly, the performance of the CMA-EMAT with different numbers of magnets was investigated by finite element simulations. Then, the CPC was proposed to replace the CMA with an optimized designed on its size. The CPC-EMAT is easier to fabricate compared to the CMA-EMAT. Finally, experimental tests were conducted for systematic validations on the transducer properties. Simulation and experimental results show that the CPC-EMAT can successfully generate the desirable and acceptable omnidirectional SH0 waves. The proposed CPC-EMAT is anticipated to find widespread application in SH-typed guided wave-based SHM.

Electronic Current Density Induced by Uniform Magnetic Fields in Clarenes.

Some planar and non-planar clarenes have been studied using maps of magnetically induced quantum-mechanical current density and tools from differential topology to assess their magnetic response in connection with recent results by Du and Wang. Bond current strengths have been computed to estimate quantitative measures. Isosurfaces of the divergence of induced Lorentz force density have been shown to provide useful additional criteria, especially in the case of non-planar clarenes.

Fano cavity test and investigation of the response of the Roos chamber irradiated by proton beams in perpendicular magnetic fields up to 1 T.

Objective. The aim of this work is to investigate the response of the Roos chamber (type 34001) irradiated by clinical proton beams in magnetic fields.Approach. At first, a Fano test was implemented in Monte Carlo software package GATE version 9.2 (based on Geant4 version 11.0.2) using a cylindrical slab geometry in a magnetic field up to 1 T. In accordance to an experimental setup (Fuchset al2021), the magnetic field correction factorskQB⃗of the Roos chamber were determined at different energies up to 252 MeV and magnetic field strengths up to 1 T, by separately simulating the ratios of chamber signalsMQ/MQB⃗,without and with magnetic field, and the dose-conversion factorsDw,QB⃗/Dw,Qin a small cylinder of water, with and without magnetic field. Additionally, detailed simulations were carried out to understand the observed magnetic field dependence.Main results. The Fano test was passed with deviations smaller than 0.25% between 0 and 1 T. The ratios of the chamber signals show both energy and magnetic field dependence. The maximum deviation of the dose-conversion factors from unity of 0.22% was observed at the lowest investigated proton energy of 97.4 MeV andB⃗= 1 T. The resultingkQB⃗factors increase initially with the applied magnetic field and decrease again after reaching a maximum at around 0.5 T; except for the lowest 97.4 MeV beam that show no observable magnetic field dependence. The deviation from unity of the factors is also larger for higher proton energies, where the maximum lies at 1.0035(5), 1.0054(7) and 1.0069(7) for initial energies ofE0= 152, 223.4 and 252 MeV, respectively.Significance. Detailed Monte Carlo studies showed that the observed effect can be mainly attributed to the differences in the transport of electrons produced both outside and inside of the air cavity in the presence of a magnetic field.

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.

On Thermal and Electrodynamic Aspects of the Superconductive Transition Process.

In a classic paper of 1960, W. H. Cherry and J. I. Gittleman discussed various thermal and electrodynamic aspects of the superconductive transition process relevant to practical applications. In a section of the paper that has remained unnoticed, they proposed a physical model for the Meissner effect. Earlier in 1940-1943, in work that has also remained unnoticed, K. M. Koch had introduced related physical ideas to explain the Meissner effect. Still earlier in 1937, J. C. Slater proposed a model to explain the perfect diamagnetism of superconductors. None of these ideas are part of the conventional London-BCS understanding of superconductivity, yet I will argue that they are essential to understand the Meissner effect, the most fundamental property of superconductors. The unconventional theory of hole superconductivity unifies and extends these ideas. A key missing element in the conventional theory as well as in these early theories is electron-hole asymmetry. A proper understanding of the Meissner effect may help with practical applications of superconductors, as well as to find new superconducting materials with desirable properties.

Wireless Magnetoelectrochemical Induction of Rotational Motion.

Electromagnetically induced rotation is a key process of many technological systems that are used in daily life, especially for energy conversion. In this context, the Lorentz force-induced deviation of charges is a crucial physical phenomenon to generate rotation. Herein, they combine the latter with the concept of bipolar electrochemistry to design a wireless magnetoelectrochemical rotor. Such a device can be considered as a wet analog of a conventional electric motor. The main driving force that propels this actuator is the result of the synergy between the charge-compensating ion flux along a bipolar electrode and an external magnetic field applied orthogonally to the surface of the object. The trajectory of the wirelessly polarized rotor can be controlled by the orientation of the magnetic field relative to the direction of the global electric field, producing a predictable clockwise or anticlockwise motion. Fine-tuning of the applied electric field allows for addressing conducting objects having variable characteristic lengths.

Longer duration entry mitigates nystagmus and vertigo in 7-Tesla MRI.

Introduction: Patients and technologists commonly describe vertigo, dizziness, and imbalance near high-field magnets, e.g., 7-Tesla (T) magnetic resonance imaging (MRI) scanners. We sought a simple way to alleviate vertigo and dizziness in high-field MRI scanners by applying the understanding of the mechanisms behind magnetic vestibular stimulation and the innate characteristics of vestibular adaptation. Methods: We first created a three-dimensional (3D) control systems model of the direct and indirect vestibulo-ocular reflex (VOR) pathways, including adaptation mechanisms. The goal was to develop a paradigm for human participants undergoing a 7T MRI scan to optimize the speed and acceleration of entry into and exit from the MRI bore to minimize unwanted vertigo. We then applied this paradigm from the model by recording 3D binocular eye movements (horizontal, vertical, and torsion) and the subjective experience of eight normal individuals within a 7T MRI. The independent variables were the duration of entry into and exit from the MRI bore, the time inside the MRI bore, and the magnetic field strength; the dependent variables were nystagmus slow-phase eye velocity (SPV) and the sensation of vertigo. Results: In the model, when the participant was exposed to a linearly increasing magnetic field strength, the per-peak (after entry into the MRI bore) and post-peak (after exiting the MRI bore) responses of nystagmus SPV were reduced with increasing duration of entry and exit, respectively. There was a greater effect on the per-peak response. The entry/exit duration and peak response were inversely related, and the nystagmus was decreased the most with the 5-min duration paradigm (the longest duration modeled). The experimental nystagmus pattern of the eight normal participants matched the model, with increasing entry duration having the strongest effect on the per-peak response of nystagmus SPV. Similarly, all participants described less vertigo with the longer duration entries. Conclusion: Increasing the duration of entry into and exit out of a 7T MRI scanner reduced or eliminated vertigo symptoms and reduced nystagmus peak SPV. Model simulations suggest that central processes of vestibular adaptation account for these effects. Therefore, 2-min entry and 20-s exit durations are a practical solution to mitigate vertigo and other discomforting symptoms associated with undergoing 7T MRI scans. In principle, these findings also apply to different magnet strengths.

On the optimized energy transport rate of magnetized micropolar fluid via ternary hybrid ferro-nanosolids: A numerical report.

In the current era, a chemical, industrial, or production process may not be devoid of heat transfer processes through fluids. This is seen in evaporators, distillation units, dryers, reactors, refrigeration and air conditioning systems, and others. On the other hand, the micropolar model effectively simulates microstructured fluids like animal blood, polymeric suspensions, and crystal fluid, paving the way for new potential applications based mainly on complex fluids. This investigation attempts to figure out and predict the thermal behavior of a polar fluid in motion across a solid sphere while considering the Lorentz force and mixed convection. To support the original fluid's thermophysical characteristics, two types of ternary hybrid ferro-nanomaterials are used. The problem is modelled using a single-phase model. Then, using the Keller box approximation, a numerical finding is obtained. The study reveals that Increasing the volume fraction of the ternary hybrid nonsolid results in optimized values of Nusselt number, velocity, and temperature. The presence of Lorentz forces effectively mitigates flow strength, skin friction, and energy transfer rate. The mixed convection factor contributes significantly to enhanced energy transfer and improved flow scenarios. For maximum heat transfer efficiency, employing Fe3O4-Cu-SiO2 is recommended over Fe3O4-Al2O3-TiO2.

Rotating Lorentz Force Magnetic Bearings' Dynamics Modeling and Adaptive Controller Design.

To address the issues of our agile satellites' poor attitude maneuverability, low pointing stability, and pointing inaccuracy, this paper proposes a new type of stabilized platform based on seven-degree-of-freedom Lorentz force magnetic levitation. Furthermore, in this study, we designed an adaptive controller based on the RBF neural network for the rotating magnetic bearing, which can improve the pointing accuracy of satellite loads. To begin, the advanced features of the new platform are described in comparison with the traditional electromechanical platform, and the structural characteristics and working principle of the platform are clarified. The significance of rotating magnetic bearings in improving load pointing accuracy is also clarified, and its rotor dynamics model is established to provide the input and output equations. The adaptive controller based on the RBF neural network is designed for the needs of high accuracy of the load pointing, high stability, and strong robustness of the system, and the current feedback inner loop is added to improve the system stiffness and rapidity. The final simulation results show that, when compared to the PID controller and robust sliding mode controller, the controller's pointing accuracy and anti-interference ability are greatly improved, and the system robustness is strong, which can effectively improve the pointing accuracy and pointing stability of the satellite/payload, as well as provide a powerful means of solving related problems in the fields of laser communication, high score detection, and so on.

Dual function of magnetic field in enhancing antibiotic wastewater treatment by an integrated photocatalysis and fluidized bed biofilm reactor (FBBR).

The integrated photocatalysis and fluidized bed biofilm reactor (FBBR) is an attractive wastewater treatment technique for managing wastewater containing antibiotics. However, the fast recombination of photoinduced charge and low microbial activity limit the degradation and mineralization efficiency for antibiotics. To address this, we attempt to introduce magnetic field (MF) to the integrated system with B-doped Bi3O4Cl as the photocatalysts to effectively improve removal and mineralization of ciprofloxacin (CIP). As a consequence, the degradation rate reaches 96% after 40 d in integrated system with MF. The biofilm inside the integrated system with MF carrier can mineralize the photocatalytic products, thereby increasing the total organic carbon (TOC) degradation rate by more than 32%. The electrochemical experiment indicates the Lorentz force generated by MF can accelerate charge separation, increasing the electron concentration. Simultaneously, the increased amounts of electrons lead to the generation of more ·OH and ·O2-. MF addition also results in increased biomass, increased biological respiratory activity, microbial community evolution and accelerated microbial metabolism, enabling more members to biodegrade photocatalytic intermediates. Therefore, applied MF is an efficient method to enhance CIP degradation and mineralization by the integrated system.

Influence of Traps and Lorentz Force on Charge Transport in Organic Semiconductors.

Charge transport characteristics in organic semiconductor devices become altered in the presence of traps due to defects or impurities in the semiconductors. These traps can lead to a decrease in charge carrier mobility and an increase in recombination rates, thereby ultimately affecting the overall performance of the device. It is therefore important to understand and mitigate the impact of traps on organic semiconductor devices. In this contribution, the influence of the capture and release times of trap states, recombination rates, and the Lorentz force on the net charge of a low-mobility organic semiconductor was determined using the finite element method (FEM) and Hall effect method through numerical simulations. The findings suggest that increasing magnetic fields had a lesser impact on net charge at constant capture and release times of trap states. On the other hand, by increasing the capture time of trap states at a constant magnetic field and fixed release time, the net charge extracted from the semiconductor device increased with increasing capture time. Moreover, the net charge extracted from the semiconductor device was nearly four and eight times greater in the case of the non-Langevin recombination rates of 0.01 and 0.001, respectively, when compared to the Langevin rate. These results imply that the non-Langevin recombination rate can significantly enhance the performance of semiconductor devices, particularly in applications that require efficient charge extraction. These findings pave the way for the development of more efficient and cost-effective electronic devices with improved charge transport properties and higher power conversion efficiencies, thus further opening up new avenues for research and innovation in this area of modern semiconductor technology.

Remote targeted electrical stimulation.

Objective:The ability to generate electric fields in specific targets remotely would transform manipulations of processes that rest on electrical signaling.Approach:This article shows that focal electric fields are generated from distance by combining two orthogonal, remotely applied energies-magnetic and focused ultrasonic fields. The effect derives from the Lorentz force equation applied to magnetic and ultrasonic fields.Main results:We elicited this effect using standard hardware and confirmed that the generated electric fields align with the Lorentz equation. The effect significantly and safely modulated human peripheral nerves and deep brain regions of non-human primates.Significance:This approach opens a new set of applications in which electric fields are generated at high spatiotemporal resolution within intact biological tissues or materials, thus circumventing the limitations of traditional electrode-based procedures.