Rotating Magnetic Field Research Articles

Adiabatic theory of one-dimensional curved polariton waveguides

We construct a general theory of adiabatic propagation of spinor exciton polaritons in waveguides of arbitrary shape, accounting for the effects of TE-TM splitting in linear polarizations and Zeeman splitting in circular polarizations. The developed theory is applied for the description of waveguides of periodically curved shape. We show that in this geometry the periodic rotation of the effective in-plane magnetic field produced by TE-TM interaction results in a nontrivial band-gap structure, which can be additionally tuned by application of an external magnetic field. It is also demonstrated that spin-dependent interactions between polaritons lead to the formation of stable gap solitons.

Increase of ibuprofen penetration through the skin by forming ion pairs with amino acid alkyl esters and exposure to the electromagnetic field

A method of increasing the permeability of ibuprofen through the skin using a rotating magnetic field (RMF) is presented. This study evaluated whether 50 Hz RMF modifies ibuprofen’s permeability through the skin. Ibuprofen and its structural modifications in the form of ibuprofenates of isopropyl esters of L-amino acids such as L-valine, L-phenylalanine, L-proline, and L-aspartic acid were used in the research. To this end, Franz cells with skin as membrane were exposed to 50 Hz RMF with 5% ibuprofen and its derivatives in an ethanol solution for 48 h. Following the exposures, the amount of penetrated compound was analysed. Regardless of the compound tested, a significant increase in drug transport through the skin was observed. The differences in the first 30 min of permeation are particularly noticeable. Furthermore, it was shown that using RMF increases the permeability of ibuprofen from 4 to 244 times compared to the test without the RMF. The greatest differences were observed for unmodified ibuprofen. However, it is noteworthy that the largest amounts of the active substance were obtained with selected modifications and exposure to RMF. The RMF may be an innovative and interesting technology that increases the penetration of anti-inflammatory and anti-ache drugs through the skin.

Radial Transport of Io Plasma From the Inner Magnetosphere to the Tail

AbstractThe solar wind‐Jovian magnetosphere‐ionosphere interaction is studied from the global magnetohydrodynamic simulation. The calculation considers the high‐speed solar wind, Io plasma emission, high‐speed rotation, ionospheric ions, and precession of magnetic field, and consequently reproduces the confinement of Jovian magnetic field, distributions of O+ and H+, supply of H+ by the polar wind, the interchange instability, and the current system that maintains co‐rotation. The radial transport process of plasma generated from Io is traceable from this solution, such that the transport mechanism gradually changes from the Io torus to the distant tail. In the transport of Io plasma, the precession plus interchange instability is effective near 10–15 Rj, interchange instability is predominant around 15–20 Rj, and the centrifugal force is predominant beyond 25 Rj. The current system supplies torque from the planet to co‐rotating plasma beyond 25 Rj to compensate the rotation delay. The associated upward field‐aligned current (FAC) is connected to the main emission (ME) in the ionosphere. The polar emission (PE) position coincides with that of downward feedback current of upward FAC causing the ME. High‐speed polar wind develops in the ME and in the polar cap, while slow polar wind develops in lower latitudes. In the middle of transport, Io plasma is mixed around 15 Rj with H+ supplied from the ionosphere by the low‐speed polar wind. Afterward, mixed plasma diffuses outward. The equatorial diffuse emission occurs in the projected position of the plasma mixing process.

Magnetic Bucket Brigade Transport Networks for Cell Transport

AbstractControlled transport of biological cells in biomedical applications such as sorting, cell sequencing, and assembly of multicellular structures is a technological challenge. Research areas such as drug delivery or tissue engineering can benefit from precise cell location resulting in faster response rates or more complex tissue structures. Using computational methods, different soft magnetic elements with curved edges are designed to form a transport network, enabling transport and all functionalities for the manipulation of microbeads and cells on surfaces by rotational magnetic fields. Building blocks with bimodal functionalities due to segments of differently curved edges permit breakpoints as well as switchable transport via splitting and combining elements. Connecting the elements, networked paths are realized which allow variable movement patterns of magnetic carriers and cells. The direction of magnetic field rotation is altered to direct the beads and cells into different transport lines, and the exact timing is not critical. The networks are used to achieve deterministic movement of microbeads and cells with minimal intervention. Programmed transport over one millimeter with cell transport velocities of several micrometers per s is demonstrated. Based on scalable microchip technology, the networks can be integrated with CMOS‐compatible materials and straightforwardly combined with sensing and diagnostic structures.

Heat transport in inclined flow towards a rotating disk under MHD

Flow towards a rotating disk is of highly practical significance in numerous engineering applications such as Turbine disks, rotary type machine systems and many more. In light of this, the current work is an attempt to explore MHD oblique flow towards a rotating disk. Hydromagnetic effects in addition to heat transfer is taken into consideration. The flow governing Partial Differential Equations are altered to a system to coupled non-linear Ordinary Differential Equations through scaling group of transformations which afterwards are tackled using Shooting Algorithm. The impact of obliqueness parameter γ, rotation ratio parameter alpha and magnetic field parameter M on 2-dimensional and 3-dimensional stream contours are presented. Location of the shear center varies with magnetic field parameter. Heat flow at the disk surface boosts with magnet field parameter M and rotation ratio parameter alpha.

On Instability of a Dusty Stellar Atmosphere in Stern’s Type Configuration

The thermal-convective instability of a stellar atmosphere in the presence of a stable solute gradient in Stern’s type configuration is studied in the presence of suspended particles. The criteria for monotonic instability are derived which are found to hold well in the presence of uniform rotation and uniform magnetic field, separately, on the thermosolutal-convective instability of a stellar atmosphere in the presence of suspended particles.

Magnetically Actuable Complex‐Shaped Microgels for Spatio‐Temporal Flow Control

AbstractComplex‐shaped microgels are promising building blocks for soft metamaterials. Their active and remote orientational control provides significant potential in architecting them in time and space. This work describes the use of magnetically actuable microgels of complex shape for spatio‐temporal flow control and showcases the concept for microfluidic impellers. First, the fabrication of complex‐shaped magnetically actuable poly(ethylene glycol) diacrylate based microgels via stop‐flow lithography is presented. The microgels comprise a pre‐programmed magnetic moment set by pre‐aligned maghemite nanospindles during the fabrication step. This feature allows the microgels to be positioned in a static magnetic field and rotate under application of a rotating external field. The dependence of the magnetic field rotation rate and strength, maghemite content, and microgel shape on the magnetic response of the microgels is comprehensively quantified. Finally, the magnetic complex‐shaped microgels are integrated as actuable impellers in a microfluidic chip. The microgels are positioned in space by polymerizing them around fixed poly(dimethylsiloxane) (PDMS) pillars. Free rotation around the PDMS pillar is achieved due to the oxygen inhibition layer at the chip and pillar surface. The versatility of the fabrication methodology is showcased by the investigation of in‐chip mixing in a microfluidic device consisting of soft responsive impellers.

Fast Error Calibration for Three-Axis SQUID Magnetometers Based on Full-Space Rotational and Frequency-Controllable Magnetic Field

In order to overcome the limitations of the traditional error calibration method for three-axis superconducting quantum interference device (SQUID) magnetometers, this article presents a fast error calibration method for three-axis SQUID magnetometers. In the proposed method, a full-space rotational and frequency-controllable magnetic field with constant total field intensity can be generated by a triaxial Helmholtz coil. Meanwhile, the nonorthogonal error, zero offset error, and proportional coefficient error of the three-axis SQUID magnetometers, which measure the relative value rather than the absolute value, can be accurately solved by an error modeling and ellipsoid fitting theory. Compared with the traditional scalar calibration method, this method replaces the rotation of Dewar and three-axis SQUID magnetometers with a rotating magnetic field, thus avoiding the interference and influence of motion. Compared with the traditional vector calibration method, this method does not need to ensure the alignment between the three-axis SQUID magnetometers and triaxial Helmholtz coil. Moreover, the interference of low-frequency magnetic field can be suppressed by shortening the period of rotating magnetic field. Simulation and experiments prove the effectiveness of this method. After calibration by the proposed method, the root-mean-square error is reduced to 0.414 from 138.411 nT in the electromagnetic shielding room. Repetitive and comparative experiments with the traditional method in field also prove the superiority and stability of the proposed method.

Magneto-mechanical therapeutic effects and associated cell death pathways of magnetic nanocomposites with distinct geometries.

Recent years have witnessed important developments in the emerging field of magneto-mechanical therapies. While such approaches have been demonstrated as a highly efficient route to augment, complement, or entirely replace other therapeutic strategies, important aspects are still poorly understood. Among these, the dependence between the cell death pathway and the geometry of magnetic nanocomposites enabling magneto-mechanical therapies under a low-frequency rotating magnetic field (RMF) is yet to be deciphered. To provide insights into this important problem, we evaluate the cell death pathway for two magnetic nanocomposites with highly distinct geometries: Zn0.2Fe2.8O4-PLGA magnetic nanospheres (MNSs) and Zn0.2Fe2.8O4-PLGA magnetic nanochains (MNCs). We show that under exposure to an RMF, the MNSs and the MNCs exhibit a corkscrewed circular propulsion mode and a steering propulsion mode, respectively. This distinct behavior, with important implications for the associated magneto-mechanical forces exerted by these nanomaterials on surrounding structures (e.g., the cellular membrane), depends on their specific geometries. Next, using numerical simulations and cell viability experiments, we demonstrate that the field strength of the RMF and the rotating speed of the MNSs or MNCs have strong implications for their magneto-mechanical therapeutic performance. Last, we reveal that the magneto-mechanical effects of MNSs are more prone to induce cell apoptosis, whereas those of the MNCs favor instead cell necrosis. Overall, this work enhances the current understanding of the dependences existing between the magneto-mechanical therapeutic effects of magnetic nanocomposites with different geometries and associated cell death pathways, paving the way for novel functionalization routes which could enable significantly enhanced cures and biomedical tools. STATEMENT OF SIGNIFICANCE.

Control of coexistent phase by rotation of magnetic field in a metamagnetic FeRh thin film

Here, we report the change of the FM and AF coexistent state in a MPTM FeRh thin film by simply rotating of the magnetic field. We find that the resistance of the coexistent phase can be changed by up to 19% by the rotation of the magnetic field. This kind of resistance change is obviously different from the usual anisotropic magnetoresistance in metallic materials whether in the angle-dependent behavior or in the magnitude. These results show another way to control the FM-AF coexistent phase, which determines the multifunctional properties of the MPTMs.

Transition to Equilibrium and Coherent Structure in Ideal MHD Turbulence

Transition of ideal, homogeneous, incompressible, magnetohydrodynamic (MHD) turbulence to near-equilibrium from non-equilibrium initial conditions is examined through new long-time numerical simulations on a 1283 periodic grid. Here, we neglect dissipation because we are primarily concerned with behavior at the largest scale which has been shown to be essentially the same for ideal and real (forced and dissipative) MHD turbulence. A Fourier spectral transform method is used to numerically integrate the dynamical equations forward in time and results from six computer runs are presented with various combinations of imposed rotation and mean magnetic field. There are five separate cases of ideal, homogeneous, incompressible, MHD turbulence: Case I, with no rotation or mean field; Case II, where only rotation is imposed; Case III, which has only a mean magnetic field; Case IV, where rotation vector and mean magnetic field direction are aligned; and Case V, which has nonaligned rotation vector and mean field directions. Dynamic coefficients are predicted by statistical mechanics to be zero-mean random variables, but largest-scale coherent magnetic structures emerge in all cases during transition; this implies dynamo action is inherent in ideal MHD turbulence. These coherent structures are expected to occur in Cases I, II and IV, but not in Cases III and V; future studies will determine whether they persist.

Quantifying the hybrid flow and aperture forming of liquid metals immersed in NaOH solution under rotating magnetic field

AbstractLiquid metal (LM) immersed in solutions exhibited profound fluidic phenomena under various working situations. With persistent research endeavor, a growing number of intriguing phenomena along this direction have been increasingly disclosed. Among the many critical issues, quantifying the hybrid flow of LMs and surrounding solutions often encounters tough challenges due to the large property differences between the two fluids, including density, electrical and fluidic characteristics, and so forth. Especially, when the electromagnetic field is involved, the problems would become ever complicated. In this article, to characterize the hybrid fluids of LM and NaOH solution under rotating magnetic field (RMF), we established a coupled three‐dimensional model considering magnetic effect on the two‐phase flow. The computational prediction of the model was validated through comparing the simulated morphological features of LM with the experimental measurements at different rotational speeds of magnetic field. Finally, two phenomena were revealed with potential applications interpreted: (1) LM would accelerate the solution due to their difference in viscosity; (2) an asymmetric flow and tunable hole formation under RMF will occur due to the surface tension redistribution on LM. The present works are expected to provide reliable guidance for quantifying the multiphase flow behaviors of hybrid fluids composed of LM and other liquids. The revealed hole size dominated LM aperture is especially useful for developing future smart optical switch and electromagnetic shielding devices.

Multifunctional Fe3O4 Nanoparticles Filled Polydopamine Hollow Rods for Antibacterial Biofilm Treatment.

This work reports the use of mesoporous silica rods as templates for the step-wise preparation of multifunctional Fe3O4 NPs filled polydopamine hollow rods (Fe3O4@PDA HR). The capacity of as-synthesized Fe3O4@PDA HR as a new drug carrier platform was assessed by its loading and the triggered release of fosfomycin under various stimulations. It was found that the release of fosfomycin was pH dependent with ~89% of fosfomycin being released in pH 5 after 24 h, which was 2-fold higher than that in pH 7. The magnetic properties of Fe3O4 NPs and the photothermal properties of PDA enabled the triggered release of fosfomycin upon the exposure to rotational magnetic field, or NIR laser irradiation. Additionally, the capability of using multifunctional Fe3O4@PDA HR to eliminate preformed bacterial biofilm was demonstrated. Upon exposure to the rotational magnetic field, the biomass of a preformed biofilm was significantly reduced by 65.3% after a 20 min treatment with Fe3O4@PDA HR. Again, due to the excellent photothermal properties of PDA, a dramatic biomass decline (72.5%) was achieved after 10 min of laser exposure. This study offers an alternative approach of using drug carrier platform as a physical mean to kill pathogenic bacteria along with its traditional use for drug delivery.

Enhanced Ion Escape Rate During IMF Rotation Under Weak Intrinsic Magnetic Field Conditions on a Mars‐Like Planet

AbstractThe rotation of the interplanetary magnetic field (IMF) provides details of the escape mechanism that varies with the interaction between the intrinsic magnetic field and the IMF. A multispecies magnetohydrodynamic simulation is conducted on a Mars‐like planet under the conditions of a weak intrinsic magnetic field and the IMF rotating by 180° over 12 hr, which is comparable to the coronal mass ejection (CME) time scale. The total ion escape rate increases from ∼5 × 1023 s−1 to ∼3 × 1025 s−1 during the IMF rotation from due north (parallel to the assumed intrinsic magnetic field) to due south (antiparallel to the assumed intrinsic magnetic field). The escape rate increases significantly with the IMF rotating from due north to clock angles of 45°–75°, followed by a gentle increase until the IMF rotates to due south. The trigger for the large increase is multiple reconnections in the magnetospheric flank region, and the subsequent increase is due to the expansion of the reconnection area into the equatorial region. The IMF mass loading in the ionosphere is also responsible for the gentle increase with IMF clock angles above 90° in addition to the flank reconnection. The IMF rotation is a general feature for a CME. Exoplanets orbiting in the vicinity of M‐dwarfs might be frequently affected by IMF rotation, as they could be exposed to severe stellar winds such as in CME environments, and the current study could be helpful for future planned observations of the exoplanetary environment.

Experimental investigation of the effect of mechanical vibration and rotating magnetic field on the hydrothermal performance of water-Fe3O4 ferrofluid inside a rifled tube

Vibration can enhance the hydrothermal performance by disturbing the thermal boundary layer. Also, the magnetic field increases the ferrofluid mixing, thereby enhancing the heat transfer rate. In this study, an experimental analysis of ferrofluid flow inside a rifled tube under the vibration and rotational magnetic field (RMF) effects was conducted by considering different Reynolds numbers (Re), nanoparticle concentrations (φ), and rifled tube pitches (P). In the first stage, the effect of Re and φ on the hydrothermal performance of the system in the absence of the vibration and RMF was explored. In the second stage, the effect of vibration on the performance evaluation criterion (PEC) of the system was investigated. Finally, the RMF effect was considered. Based on the results, the system with P = 5 mm showed the highest PEC in all experiments. The highest PEC without the vibration and RMF effects was obtained as 1.62 for P = 5 mm and φ = 0% at Re = 2000. The highest PEC under the vibration effect (1.28) was also found for Re = 2000 but at φ of 2%, when the highest vibration acceleration (5 m/s2) was applied. Among the RMFs examined, the RMF with the counter clock-wise along with the counter clock-wise fluid flow inside the rifled tube resulted in the highest PEC of 1.62. RMF improved the PEC of the system from 1.28 to 1.62, corresponding to a 21.32% increase, under the vibration.

Effect of rotating magnetic field intensity on structure and electrical and optical properties of GaInSb crystal grown with travelling heater method

Ga1−x In x Sb(0 < x < 1) crystal is a very promising substrate material, which can be used to fabricate a variety of high-performance infrared detectors and lasers by epitaxial growth. Herein, we prepared high quality Ga0.86In0.14Sb crystal (25 mm diameter, 100 mm length) with travelling heater method applied rotating magnetic field (RMF), and revealed the effects of RMF intensity on structure and electrical and optical properties of the crystal. As the RMF intensity increased the crystal quality significantly improved, and the radial segregation of indium decreased from 0.258 to 0.031 mol% mm−1, in the center of the crystal. Similarly, the segregation of indium along the ingot between 20 to 80 mm, toward the traveling zone, decreased from 0.114 to 0.038 mol% mm−1. The dislocation density of GaInSb crystal ingot also decreased from 5.361 × 105 cm−2 to 5.295 × 103 cm−2. The electric properties of the crystal also improved, the carrier mobility increased to 1.902 × 103 from 1.358 × 103cm2 (V·s)−1, the resistivity decreased to 1.047 × 10−3 from 1.822 × 10−3 Ω·cm. Moreover, the infrared transmittance increased from 36% to 39%.

A Study of Stellar Spins in 15 Open Clusters

We analyze spectroscopic and photometric data to determine the projected inclinations of stars in 11 open clusters, placing constraints on the spin-axis distributions of six clusters. We combine these results with four additional clusters studied by Healy & McCullough and Healy et al. to perform an ensemble analysis of their spins. We find that eight out of 10 constrained clusters (80%) have spin-axis orientations consistent with isotropy, and we establish a lower limit of four out of 10 (40%) isotropic clusters at 75% confidence, assuming no correlation of spins between clusters. We also identify two clusters whose spin-axis distributions can be better described by a model consisting of an aligned fraction of stars combined with an isotropic distribution. However, the inclination values of these stars may be influenced by systematic error, and the small number of stars modeled as aligned in these two clusters precludes the interpretation that their stellar subsets are physically aligned. Overall, no cluster displays an unambiguous signature of spin alignment, and 97% of the stars in our sample are consistent with isotropic orientations in their respective clusters. Our results offer support for the dominance of turbulence over ordered rotation in clumps and do not suggest the alignment of rotation axes and magnetic fields in protostars.

Electric polarization reversal and nonlinear magnetoelectric coupling in the honeycomb antiferromagnet Fe4Nb2O9 single crystal

As a new magnetoelectric material, honeycomb-based antiferromagnet ${\mathrm{Fe}}_{4}{\mathrm{Nb}}_{2}{\mathrm{O}}_{9}$ has attracted a great deal of attention due to its prominent magnetoelectric (ME) coupling and high N\'eel temperature, while the physics of magnetoelectricity is far from understood. In the present study, we present our systematic investigations of the anisotropic ME effect, electric polarization reversal, and nonlinear ME effect of ${\mathrm{Fe}}_{4}{\mathrm{Nb}}_{2}{\mathrm{O}}_{9}$ single crystals, thus highlighting the phase diagram extended down to 10 K. Our results provide clear evidence for electric polarization reversal driven by magnetic field ($H$) along the [110] and [1-10] directions, respectively, while no such polarization reversal occurs as $H$ is applied along the [001] direction. The nonlinear ME effects and electric control of magnetism are unambiguously demonstrated. In addition, the angular-dependent probing reveals a 2\ensuremath{\theta} rotation of the induced electric polarization around the $c$ axis upon the rotation of magnetic field by an angle \ensuremath{\theta}. The electric polarization responses and concomitant ME coupling are well explained by means of the metal-ligand hybridization $p\text{\ensuremath{-}}d$ mechanism. This work represents an essential step forward in the understanding of ME coupling not only in this ${A}_{4}{M}_{2}{\mathrm{O}}_{9}$ honeycomb magnet.

Effect of compound treatment of rotating magnetic field and Al-5Ti-1B refiner on microstructure and properties of Al-5Cu alloy

The Al-5Cu alloys were prepared by different treatment methods, including adding a refiner Al-5Ti-1B, exerting a rotating magnetic field (RMF), and compound treatment of both refiner and RMF. The effects of treatment methods on the microstructure, properties, and solid solubility of the Al-5Cu alloy were investigated. The optimal magnetic field parameters and addition amount of refiner were confirmed by experiment. Results show that either RMF or adding refiner Al-5Ti-1B alone can refine the grain size, and the refining effect can be further improved by a compound refining treatment with optimized magnetic field parameters (120 A current and 8 Hz frequency) and 1.0wt.% Al-5Ti-1B refiner (RMF*+Al-5Ti-1B*). The average grain size is decreased to 68.1 µm, which is 60.8%, 21.1%, and 83.5% lower than that of the alloy treated by the optimized rotating magnetic field, the Al-5Ti-1B refiner, and the alloy without any treatment, respectively. The tensile strength and elongation of the alloy reach 232.5 MPa and 18.6%, respectively, which are obviously higher than those of the alloys treated by rotating magnetic field, Al-5Ti-1B refiner, and the alloy without any treatment, respectively. Additionally, the solid solubility of the alloy is also obviously improved compared to the alloys treated by other methods.

Quasi-stationary flow in a channel with a ferrofluid drop, induced by a rotational magnetic field

Quasi-stationary flow in a channel with a ferrofluid drop, induced by a rotational magnetic field