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The microstructure morphology, static magnetic properties, and electromagnetic absorption characteristics of nano FexCoNi alloy particles prepared by chemical liquid deposition with five different Fe content levels are investigated in this paper. The results show that spherical FexCoNi alloy particles with an average particle size of about 100–200 nm and a face-centered cubic crystal structure were obtained. All five samples exhibited soft magnetic behavior, with the saturation magnetization intensity showing an increasing-then-decreasing trend with increasing Fe content, peaking at 141.8 emu/g for Fe content x = 1.0. The dielectric constants (real and imaginary parts) of the prepared alloy particles exhibit significant differences with respect to the variation of Fe content, while the changes in the real and imaginary parts of the magnetic permeability show less pronounced effects with increasing Fe content. As the electromagnetic wave frequency increases, the real parts of the dielectric constants for all composites show minimal fluctuations, and the real parts of the magnetic permeability exhibit a decreasing trend. Moreover, the imaginary parts of the dielectric constants and magnetic permeability show an increasing followed by a decreasing trend as the frequency rises. The material with Fe content x = 1 demonstrated optimal dielectric loss performance and relatively excellent magnetic loss performance, with a sample thickness of 1.9 mm exhibiting the highest reflection loss (RLmax) of −24.2 dB and an effective absorption bandwidth of 4.48 GHz. [ABSTRACT FROM AUTHOR]

Micrometer-sized magnetic particles have been widely used in magnetic force microscopy, magnetic resonance force microscopy, and bio-sensing. To quantitatively interpret the data obtained with magnetic particles, it is important to know the magnetic properties of the particles. However, the magnetic moment of individual particle is usually too small to be measured by common instruments for samples with large volume. Here, we present a method to characterize magnetic microspheres using patterned FePt thin films as standard samples. The FePt thin film in the L 1 0 phase has perpendicular magnetic anisotropy, and the patterned features can be magnetized to near single-domain magnets, which make them suitable standards for magnetic sphere calibration with magnetic force microscopy. Multiple linear regression is used to analyze the frequency shift images and obtain the effective dipole moment of the spheres. The position of the dipole moment is obtained by minimizing the residuals in multiple linear regression with a gradient descent algorithm. Three NdFeB spheres of different diameters were measured. It was found that the magnetization increases with the increase in the diameter of the sphere, possibly due to the weakening of ferromagnetism on the surface. [ABSTRACT FROM AUTHOR]

The cellulose fibers that form washi are longer than those of regular paper made from wood pulp. Hence, the mechanical properties of washi can be higher than those of conventional paper. This study evaluated the magnetic, magnetostrictive, and tensile properties of negative magnetostrictive cobalt ferrite (CoFe2O4) particle dispersed handmade washi (washi−CoFe2O4). The CoFe2O4 additives magnetized the washi, which displayed negative magnetostriction with the fiber direction perpendicular to the magnetic field and in the parallel fiber direction. Concerning the mechanical properties, the washi−CoFe2O4 displayed an elongation of up to 77% after yielding. [ABSTRACT FROM AUTHOR]

The development of projection‐based stereolithography 3D printing techniques has provided a powerful approach to fabricate millimeter scale functional devices with complex structures. However, the current processes face challenges in frequent switching between multiple materials or processes, resulting in low efficiency and accuracy during the fabrication of bifunctional devices. To address these challenges, chemical deposition is utilized to modify graphene nanoplatelets (GNs) with Fe3O4 magnetic particles and incorporate them into the photosensitive resin, resulting in the development of a novel bifunctional printing material with magnetic and locally conductive properties. Furthermore, the localized conductivity of devices is controlled by an electric‐field‐assisted alignment process of the magnetic GNs (mGNs) during the printing process. Herein, this single‐material projection‐based stereolithography allows for the simultaneous fabrication of magnetic and locally conductive millimeter scale bifunctional devices without switching between multiple materials or processes. A magnetically driven circuit switch and signal coding gear are fabricated as demonstrations. This work significantly improves the efficiency and accuracy of fabricating millimeter scale bifunctional devices, thereby facilitating their application in the fabrication of miniaturized and integrated devices. [ABSTRACT FROM AUTHOR]

We report a transverse optical torque exerted on a conventional isotropic spherical particle in a direction perpendicular to that of the illuminating wave propagation. By using full-wave simulations and deriving an analytical expression of the transverse optical torque for particle of arbitrary size, the origin of this transverse optical torque is traced exclusively to the magnetic part of the spin angular momentum, regardless of the size and composition of the illuminated particle. To our surprise, for a non-magnetic dielectric particle, the transverse optical torque is found to originate mainly from the magnetic response of the particle, even when the particle size is much smaller than the illuminating wavelength. This is contrary to the general intuition that the electric response of a non-magnetic dielectric particle dominates its magnetic response in the mechanical effect of light, especially in the Rayleigh limit. [ABSTRACT FROM AUTHOR]

Continuous flow magnetophoresis represents a common technique for actively separating particles within a fluid. For separation systems design, accurately predicting particle behaviour helps to characterise system performance, typically measured by the separation efficiency (SE). While finite element method (FEM) simulations offer high accuracy, they demand extensive computational resources. Alternatively, results can be achieved more quickly with simplified numerical models that use analytical descriptions of fluid flow, magnetic fields, and particle movement. In this research, we model a millifluidic system that separates magnetic particles using magnetophoresis. Therefore, we (1) develop a simple numerical model that can simulate continuous flow magnetophoresis for rectangular channels in two and three dimensions, (2) introduce a novel and simple approach to calculate the SE, and (3) quantify the effects of model assumptions in flow profile and dimensions on SE. Our method for estimating SE considers particle flux variation across the channel's cross-section due to the flow profile. The results are compared to an FEM model developed in COMSOL. The obtained three-dimensional simulation model computes results in seconds, around 180 times faster than the FEM approach, while deviating less than 2% from the FEM results. A comparison of the different two-dimensional and three-dimensional models underscores the significant influence of the flow profile and the SE calculation method on the result. The two dimensional models generally overestimate the SE of up to 15% due to their lower peak flow velocity. However, using a constant flow velocity leads to good agreement for high SE due to the overlap of differences in flow profile and SE calculation. [ABSTRACT FROM AUTHOR]

Side-chain liquid crystal polymers have been mixed with ferromagnetic particles, and the formation of a monodomain in magnetic fields studied. At relatively low concentrations, the presence of ferroparticles substantially speeds up the rate of formation of a monodomain within the magnetic field, and, at a given concentration of ferroparticles, that rate is independent of the magnetic field's strength. In this way, the rapid formation of a monodomain is possible at magnetic field strengths far lower those required for the liquid crystal polymer alone. This is anticipated to be very helpful in the fabrication of devices based on monodomain liquid crystal elastomers. Wide-angle x-ray scattering has been used to monitor the formation of the monodomain and small-angle x-ray scattering gives some indication of the ferroparticles' behaviour. A model is developed to explain their behaviour. The alignment properties of the ferroparticles are related to their ability to form chains under the influence of very low magnetic fields; these chains are of relatively low stability and may become disrupted after long periods of time, high magnetic fields, or high concentrations. In general, the best results for alignment were at volume fractions below 1%, and under these conditions there is the potential for producing monodomain samples with improved properties; in particular, shape changes with temperature are significantly larger as a result of improved backbone orientation. Experiments involving monodomain formation and director realignment suggest that the presence of ferroparticles results in a modification of the mechanism for alignment development, driven by the organization of the polymer backbone, as a consequence of the constraints offered by the morphology of the chains of the ferroparticles. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles (MNPs) have garnered significant attention in biomedical applications. Due to their large surface area and tunable properties, MNPs are used in microfluidic systems, which allow for the manipulation and control of fluids at micro- or nanoscale. Using microfluidic systems allows for a faster, less expensive, and more efficient approach to applications like bioanalysis. MNPs in microfluidics can precisely identify and detect bioanalytes on a single chip by controlling analytes in conjunction with magnetic particles (MPs) and separating various particles for analytical functions at the micro- and nanoscales. Numerous uses for these instruments, including cell-based research, proteomics, and diagnostics, have been reported. The successful reduction in the size of analytical assays and the creation of compact LOC platforms have been made possible with the assistance of microfluidics. Microfluidics is a highly effective method for manipulating fluids as a continuous flow or discrete droplets. Since the implementation of the LOC technology, various microfluidic methods have been developed to improve the efficiency and precision of sorting, separating, or isolating cells or microparticles from their original samples. These techniques aim to surpass traditional laboratory procedures. This review focuses on the recent progress in utilizing microfluidic systems that incorporate MNPs for biological applications. [ABSTRACT FROM AUTHOR]

Coprinus comatus is an edible mushroom and its fermented product possesses antioxidant activity. In this study, to further enhance the antioxidant activity and improve the reusability of the strain, calcium alginate hydrogel was used as the carrier for embedding and immobilizing Coprinus comatus. The effects of CaCl2 concentration, sodium alginate concentration, microsphere diameter, and the amount of magnetic particle on the antioxidant activity of fermented products were investigated. The results showed that the magnetic immobilized microsphere prepared by 2.50% CaCl2, 2.00% sodium alginate and 0.50% Fe3O4 had the best fermentation antioxidant activity (EC50 was 0.43 ± 0.01 mg/mL) when the diameter was 5 mm, which increased by 24.56% compared to the initial activity. Besides, the microsphere showed strong reusability, the antioxidant activity was still better than the free strain after being used five times. This study not only enhanced the antioxidant activity of Coprinus comatus fermented product through immobilization, but also provided an effective method for microbial fermentation. [ABSTRACT FROM AUTHOR]

Over the past decade, significant advancements in micro‐nano robots have enabled non‐invasive operations in hazardous, confined environments, particularly targeting persistent bacterial biofilms in hard‐to‐reach areas. However, many of these robots are limited by poor magnetic properties, hindering their effectiveness against biofilms. This study proposes a novel strategy using a swarm with strong magnetic effects (Hercules swarm) combined with near‐infrared (NIR) light for effective biofilm eradication. Carbonyl iron particles coated with polydopamine (CI@PDA), averaging ≈3 µm in diameter, demonstrate clustering and significant magneto‐force under a rotating magnetic field due to their large magnetic saturation. This enables the Hercules swarm to achieve rapid delivery (100 mm s−1), efficient cargo transport (carrying twice its own weight), and effective catheter clearance (1 mm min−1). The controllable motion and high photothermal activity enable precise biofilm eradication without toxic agents. The aggregation of magnetic particles into chains and their rotation are explored by improved particle dynamic model. Simulations also reveal enhanced fluid convection and mechanical pressure around the particle chain. Due to its easy operation, straightforward controllability, and environmental compatibility, the magnetic Hercules swarm emerges as a promising treatment modality for eliminating biofilms entrenched within intricate, narrow, and convoluted medical implants or industrial conduits. [ABSTRACT FROM AUTHOR]

Spider pulsars are compact binary systems composed of a millisecond pulsar and a low-mass companion. Their X-ray emission – modulated on the orbital period – is interpreted as synchrotron radiation from high-energy electrons accelerated at the intrabinary shock. We perform global two-dimensional particle-in-cell simulations of the intrabinary shock, assuming that the shock wraps around the companion star. When the pulsar spin axis is nearly aligned with the orbital angular momentum, we find that the magnetic energy of the relativistic pulsar wind – composed of magnetic stripes of alternating field polarity – efficiently converts to particle energy at the intrabinary shock, via shock-driven reconnection. The highest energy particles accelerated by reconnection can stream ahead of the shock and be further accelerated by the upstream motional electric field. In the downstream, further energization is governed by stochastic interactions with the plasmoids/magnetic islands generated by reconnection. We also extend our earlier work by performing simulations that have a larger (and more realistic) companion size and a more strongly magnetized pulsar wind. We confirm that our first-principles synchrotron spectra and light curves are in good agreement with X-ray observations. [ABSTRACT FROM AUTHOR]

A measurement of the cosmic ray anisotropy on the arrival directions of elementary particles (electrons, positrons and protons) has been performed in galactic coordinates by the Alpha Magnetic Spectrometer onboard the International Space Station. The analysis is based on the sample of events collected in the first 10 years of data taking. The results are consistent with isotropy for all cosmic ray species and upper limits on the dipole amplitude have been computed. In particular, 95 % credible interval upper limits of δ < 1.50 % and δ < 0.34 % are obtained for positrons and electrons, respectively, above 16 GeV. On the other hand, the upper limit to the dipole anisotropy of protons above 200 GV is found to be δ < 0.30 %. [ABSTRACT FROM AUTHOR]

Magnetic field lines in magnetohydrodynamic turbulence are stochastic curves and, therefore, understanding their structure is a difficult problem of theoretical physics. One way to study the properties of such field lines is to perform simulations in which field line equations are solved numerically. In most previous articles studies have been performed in the context of the two-component turbulence model where one assumes a superposition of slab and two-dimensional modes. In the current paper we perform simulations for so-called noisy slab turbulence which is an example for three-dimensional turbulence with small Kubo numbers. We discuss in detail the challenges of the numerical magnetic field creation for this type of turbulence, perform the simulations, and compare our findings with analytical theory. It is demonstrated that a large number of wave modes is needed in order to obtain accurate results. Furthermore, we also show that analytical theories are very accurate for this type of turbulence model. The obtained results will also be useful for the analytical description of energetic particle transport in the considered turbulence model. [ABSTRACT FROM AUTHOR]

With the intelligent development of magnetic particle inspection, the quality of magnetic indications formed at cracks is closely related to the accuracy of magnetic particle inspection image analysis results. The concentration of magnetic suspension is a key process parameter affecting the quality of magnetic indication formation. Hence, this study presents an online detection method based on machine vision for measuring magnetic suspension concentration. The method initially enhances the contrast of images of the pear-shaped measuring tube containing magnetic suspension and then extracts scale lines through feature analysis and morphological processing. A method for extracting the magnetic particle sedimentation area of magnetic suspension based on a dual-threshold segmentation algorithm is proposed. The contour filtering algorithm and pixel calibration method are used to obtain the magnetic particle concentration of the non-estimation and estimation areas based on scale line extraction, ultimately forming an online accurate detection method for magnetic suspension concentration values. Experiments were conducted to validate the method against different concentrations, turbidity levels, tilting angles of the pear-shaped measuring tube, and ambient brightness. The results show that the error in magnetic suspension concentration detection based on this method is within 5%. This has certain reference value for the stable control of magnetic suspension concentration and for enhancing the reliability of intelligent decision-making results in magnetic particle inspection. [ABSTRACT FROM AUTHOR]

Despite their advantages of light weight, complete coating and good formability, the poor high-temperature stability of organic materials limits their use as insulation coatings for soft magnetic powders. Therefore, a polyethyleneimine (PEI)/silicone resin (SR) double organic insulation layer was exploited to release internal stress and maintain insulation stability during the high-temperature annealing process, which achieved low core losses (Pcv) and high effective permeability (μe). Cross-sectional scanning transition images indicate that the PEI/SR layer undergoes the following evolution during annealing at 500–900°C: coating → densification → crack → rupture, implying thermal stability up to 700°C. Because of the integrity of double inorganic shells and the weak pin on magnetic domain movement, FeSiAl@PEI/SR cores annealed at 800°C deliver remarkable AC soft magnetic performance at 50 and 100 kHz, that is, low Pcv of 61.6 mW/cm3 (50 mT, 100 kHz), 121.2 mW/cm3 (100 mT, 50 kHz) and 307.3 mW/cm3 (100 mT, 100 kHz), high μe of 55.6 up to 1 MHz and 140°C, and DC bias of 51.5% at 100 Oe. Eddy current loss reaches the minimum value at 700°C and deteriorates at 800°C, and hysteresis loss continues to decrease with increasing annealing temperature, confirming the evolution of the insulation layer. Moreover, cores annealed at 700°C deliver μe of 57.6 at 1 MHz and Pcv of 278 mW/cm3 (20 mT, 1 MHz), exhibiting great potential for 1 MHz frequency power applications. [ABSTRACT FROM AUTHOR]

In order to reveal adsorption-regulation micromechanism and debonding micromechanism between wall surface and magnetorheological (MR) wall-climbing robot legs, an interparticle normal magnetic attraction (NMA) mechanics model was constructed based upon the magnetic-dipole theory. According to analysis of NMA mechanics, it was confirmed that the interparticle NMA could be intensified with enhancing magnetic-particle diameter but was weakened with ratio of adjacent magnetic-particles distance to magnetic-particle radius. It means that the adhesive capacity between MR wall-climbing robot legs and wall surface could be strengthened by increasing magnetic-particle size and decreasing interparticle distance. Furthermore, it was found that the NMA of the first particle in the magnetic chain was positively related to magnetic-particles number until the magnetic-particles number reached a critical value. Consequently, the adsorption ability between MR wall-climbing robot legs and wall surface could be effectively controlled by changing magnetic-particles number. Besides, the strongest NMA appeared at the middle of the magnetic chain. However, the weakest NMA locates at both ends of the magnetic chain. Thus, it could be concluded that the end of the magnetic chain would be separated from wall surface rather than fracture occurred in the middle of the magnetic chain when the MR wall-climbing robot legs divorced from wall surface. [ABSTRACT FROM AUTHOR]

The following work explores the creation and advancement of a highly sensitive piezoresistive strain sensor. This sensor is composed of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) with a layer of interconnected Ni microparticles (NiMPs) on its surface. The interconnection of NiMPs was achieved through a new simple and cost-effective method using a magnetic bar. Additionally, the elasticity of the PEDOT:PSS membrane is enhanced by incorporating polyvinyl alcohol (PVA). The piezoresistive strain sensor, consisting of PEDOT:PSS, PVA, and NiMPs, was examined to assess its electrical signal, stability, and response time under various strains and bending angles, ranging from 0 to 28%. This range covers typical human body movements. The results demonstrated that the pristine PEDOT:PSS membrane has no piezoresistive effect, while the modified one with NiMPs, it shows a gauge factor value of 174 at high strain levels. Additionally, the sensor's performance was tested with human finger motions, revealing a significant response to changes in finger movement. The modified method of evenly distributing metallic particles can be used with various magnetic particles such as iron, cobalt, steel, or manganese. [ABSTRACT FROM AUTHOR]

To tailor superparamagnetic iron oxide nanoparticles (SPIONs) to the specific needs of diverse application fields, it is essential to understand not only their intrinsic properties but also their interactions with each other. Theoretical models predicting/explaining the magnetization behavior of macroscopic samples containing millions of SPIONs are intricate due to the complexity of the underlying relaxation mechanisms in alternating fields. This study introduces supraparticles (SPs) as model architectures to empirically investigate magnetic interactions within and between large SPION clusters (>100 nanoparticles (NPs)). For this purpose, NP dispersions containing SPIONs and silica (SiO2)NPs as non‐magnetic building blocks are spray‐dried to form binary SPs. Selective salt‐induced agglomeration of the two building block types before spray‐drying is utilized to tailor SP architectures, including control over SPION cluster size, shape, and proximity. Magnetic particle spectroscopy (MPS), operating under ambient conditions, reveals altered magnetization behavior for different cluster structures. Not only the nearest SPION neighbors, but the whole cluster structure up to several micrometers is decisive for the magnetization behavior. This highlights the importance of long‐range magnetic interactions. This work presents a versatile approach for designing model architectures to advance empirical interaction studies between SPIONs in macroscopic samples. [ABSTRACT FROM AUTHOR]

The initial delivery of small‐scale magnetic devices such as microrobots is a key, but often overlooked, aspect for their use in clinical applications. The deployment of these devices within the dynamic environment of the human body presents significant challenges due to their dispersion caused by circulatory flows. Here, a method is introduced to effectively deliver a swarm of magnetic nanoparticles in fluidic flows. This approach integrates a magnetically navigated robotic microcatheter equipped with a reservoir for storing the magnetic nanoparticles. The microfluidic flow within the reservoir facilitates the injection of magnetic nanoparticles into the fluid stream, and a magnetic field gradient guides the swarm through the oscillatory flow to a target site. The microcatheter and reservoir are engineered to enable magnetic steering and injection of the magnetic nanoparticles. To demonstrate this approach, experiments are conducted utilizing a spinal cord phantom simulating intrathecal catheter delivery for applications in the central nervous system. These results demonstrate that the proposed microcatheter successfully concentrates nanoparticles near the desired location through the precise manipulation of magnetic field gradients, offering a promising solution for the controlled deployment of untethered magnetic micro‐/nanodevices within the complex physiological circulatory systems of the human body. [ABSTRACT FROM AUTHOR]

Antitumor hyperthermia therapy is an emerging approach for the thermal treatment of cancer. Magnetite-based nanoparticles are very promising hyperthermia agents due to its biocompatibility and versatile application. In this study, engineered citrate functionalized magnetite nanoparticles resulted in an adequate colloid for the desire application: 12.57 nm ± 3.86, −44.5 ± 0.6 mV, hydrophilic character, and 85.2 ± 1.6 emu/g. Those citrate-functionalized magnetite colloids were embedded into a chitosan nanomatrix to obtain cluster/shell citrate-magnetite/chitosan nanoparticles with demonstrated short-term stability. In addition, freeze-drying using saccharose as cryoprotectant was used for a long-term preservation. Cluster/shell nanostructure was confirmed using Fourier transform infrared spectroscopy, X-ray diffraction analysis, thermogravimetric analysis, surface electrokinetics and thermodynamics, dynamic light scattering and high resolution transmission electron microscopy. Citrate-magnetite/chitosan nanoparticles demonstrated negligible cytotoxicity in a non-tumor cell line and adequate characteristics for parenteral administration (187.33 ± 54.85 nm and haemocompatibility). Magnetic behaviour was not affected by the chitosan shell onto the citrate-magnetite cluster of particles. Thermal enhance capacity was fully investigated using magnetic hyperthermia and photothermal modalities. Specific absorption rate values resulted for citrate-magnetite/chitosan NPs were superior to that obtained for single core particles in magnetic hyperthermia (393 ± 45 and 239 ± 31) and photothermal therapy (384 ± 7.1 and 272 ± 0.8, respectively). Therefore, citrate-magnetite/chitosan cluster/shell nanoparticles could find antitumor hyperthermia applications by using a systemic a dual magneto-photo-thermal therapy. [Display omitted] [ABSTRACT FROM AUTHOR]

Symmetry-breaking perturbations in axisymmetric toroidal plasma configurations have a drastic impact on particle, energy, and momentum transport in fusion devices, thereby affecting their confinement properties. The perturbative modes strongly affect particles with specific kinetic characteristics through resonant mode–particle interactions. In this work, we present an analytical calculation of the kinetic q factor, enabling the identification of particles with kinetic properties that meet the resonant conditions. This allows us to predict the locations and structures of the corresponding resonant island chains, as well as the existence of transport barriers in the particle phase space. The analytical results, derived for the case of a large aspect ratio configuration, are systematically compared to numerical simulations, and their domain of validity is thoroughly investigated and explained. Our findings demonstrate that calculating the kinetic q factor and its dependence on both particle and magnetic field characteristics provides a valuable tool for understanding and predicting the resonant plasma response to non-axisymmetric perturbations. Moreover, this approach can be semi-analytically applied to generic realistic experimental equilibria, offering a low-computational-cost method for scenario investigations under various multi-scale perturbative modes. [ABSTRACT FROM AUTHOR]

In this paper, mechanisms that differentiate microrotation (i.e., particles' internal rotation) and vorticity in magnetohydrodynamic micropolar flows with magnetic particles are examined. Micropolar fluids are characterized by the asynchronization of the microrotation and the vorticity of the liquid carrier. When the microrotation is equal to the fluid's vorticity, the flow is purely Newtonian. In this context, two classical examples of micropolar magnetohydrodynamic fluids with magnetic particles are used, namely, blood and ferrofluid. The effect of all dimensionless parameters associated with the mathematical model is examined in terms of differentiating microrotation and vorticity. These dimensionless parameters are specifically calculated using the physical properties of the ferrofluid and blood. It was shown that higher values of the rotational viscosity (which are associated with smaller values of the spin relaxation time), higher values of channel's height, and higher values of the microrotation wall parameter tend to equalize microrotation and vorticity. On the other hand, the spin viscosity and the micromagnetorotation (magnetic torque) are mechanisms that differentiate microrotation and vorticity. Lorentz force does not seem to have any noticeable effect on the microrotation–vorticity difference. It is anticipated that this study will reveal the cases where a magnetohydrodynamic micropolar fluid with magnetic particles, such as blood and ferrofluid, can be simplified to a Newtonian one, which brings many benefits associated with a simplified mathematical flow model (such as smaller computational cost and less time). [ABSTRACT FROM AUTHOR]

The present study investigates surfactant–carrier interactions in non-aqueous ferrofluids with magneto-rheology at different temperatures. To the authors' knowledge, such a study has not yet been reported. For this purpose, three ferrofluids—A, B, and C—were procured from Ferrotec, which had identical particles but different surfactant–carrier combinations. The study also encompasses structural and magnetic techniques to elucidate these samples' physicochemical nature. The results show that the average magnetic size of particles (10 nm) is the same for all the three fluids. The nominal value of the surfactant chain length (4.5 nm) was derived from dynamic light scattering measurements, and the Rosensweig viscosity model and the Shliomis theory were the same. The magneto-rheological properties, e.g., shear stress vs shear rate in zero field and relative increase in ferrofluid viscosity in the applied field at two different temperatures (300 and 313 K), were fitted with Rosensweig and Shliomis models. They showed some variations in surfactant chain lengths. The results suggested the presence of surfactant–carrier interactions in these colloids. This new investigation may be useful in characterizing the stability of a ferrofluid and its practical aspects. [ABSTRACT FROM AUTHOR]

Magnetic particle spray mass spectrometry (MPS-MS), an innovative ambient ionization technique proposed by our research group, was employed to determine beta-blockers in human plasma samples. A dispersive solid phase extraction of atenolol, metoprolol, labetalol, propranolol, nadolol, and pindolol was carried out using magnetic molecularly imprinted polymer (M-MIP) particles that were attached to the tip of a metal probe, which was placed in the mass spectrometer inlet. A solvent (1% formic acid in methanol) was dispensed on the particles, and the Taylor cone was formed around them (in high voltage). The analytes were desorbed/ionized and determined by a triple quadrupole mass spectrometer. M-MIP was synthesized with oxprenolol as a pseudo-template, demonstrating good selectivity to beta-blockers compared with no-analog molecules, with an adsorption process occurring in monolayers, according to isotherm studies. Kinetic experiments indicated chemisorption as the predominant M-MIP/analyte interaction. The analytical curves were linear (R2 > 0.98), and the limit of quantification was 3 µg L−1 for all the analytes. Limits of detection ranged from 0.64 to 2.41 µg L−1. Precisions (relative standard deviation) and accuracies (relative error) ranged from 3.95 to 21.20% and -17.05 to 18.93%, respectively. MPS-MS proved to be a simple, sensitive, and advantageous technique compared with conventional approaches. The analyses were fast, requiring no chromatographic separation and without ionic suppression. The method is aligned with green chemistry principles, requiring minimal sample, solvent, and sorbent amounts. MPS-MS successfully integrates sample preparation and ambient ionization mass spectrometry and holds great potential for application with other sorbents, samples, and analytes. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles (MNPs) can be functionalized with antibodies to give them an affinity for a biomarker of interest. Functionalized MNPs (fMNPs) cluster in the presence of a multivalent target, causing a change in their magnetization. Target concentration can be proportional to the 3rd harmonic phase of the fMNP magnetization signal. fMNP clustering can also be induced with salt. Generally, salt can alter the stability of charge stabilized fMNPs causing a change in magnetization that is not proportional to the target concentration. We have developed a model system consisting of biotinylated MNPs (biotin-MNPs) that target streptavidin to study the effects of salt concentration on fMNP-based biosensing in simulated in vivo conditions. We have found that biotin-MNP streptavidin targeting was independent of salt concentration for 0.005x to 1.00x phosphate buffered saline (PBS) solutions. Additionally, we show that our biosensor's measurable concentration range (dynamic range) can be tuned with biotin density. Our results can be leveraged to design an in vivo nanoparticle (NP)-based biosensor with enhanced efficacy in the event of varying salt concentrations. [ABSTRACT FROM AUTHOR]

We report the achievement of a high coercivity (Hc) value of 3 kOe for Mn54Al46 powders produced by high-energy ball milling without any heat treatment. The ferromagnetic α-Mn(Al) alloy powders were prepared with Mn (54 at%) and Al (46 at%) as the constituent metal elements. Analysis and discussion were held regarding the potential causes of the observed enhancement in the magnetic properties of the ball-milled powders in relation to their phase composition and microstructure. The process of milling causes partial solubilisation of Al atoms in the α-Mn phase and a change in the powder magnetic characteristics from paramagnetic to ferromagnetic. The existence of γ2 and β phases was identified by XRD after long hours of the milling process. In addition, it was found that a longer milling time resulted in a smaller crystallite size, which also resulted in a decrease in magnetic saturation (Ms) but an increase in coercivity (HC). Without applying any extra heat treatment, the Mn-Al powders milled for 6 h had optimum magnetic properties: Hc = 3.0 kOe, Mr = 0.05 emu/g, Ms = 0.19 emu/g, and (BH)max = 432 J/m3. [ABSTRACT FROM AUTHOR]

This article presents a method for producing chiral ionic liquid-based polyurea microcapsules that can be magnetically separated. The method involves entrapping hydrophilic magnetic nanoparticles within chiral polyurea microspheres. The synthetic process for creating these magnetic polyurea particles involves oil-in-oil (o/o) nano-emulsification of an ionic liquid-modified magnetite nanoparticle (MNPs-IL) and an ionic liquid-based diamine monomer, which comprises a chiral bis(mandelato)borate anion, in a nonpolar organic solvent, toluene, and contains a suitable surfactant. This is followed by an interfacial polycondensation reaction between the isocyanate monomer, polymethylenepolyphenyl isocyanate (PAPI 27), and the chiral diamine monomer, which generates chiral polyurea microcapsules containing magnetic nanoparticles within their cores. The microcapsules generated from the process are then utilized to selectively adsorb either the R or S enantiomer of tryptophan (Trp) from a racemic mixture that is dissolved in water, in order to evaluate their chiral recognition capabilities. During the experiments, the magnetically separable chiral poly(ionic liquid) microcapsules, which incorporated either the R or S isomer of chiral bis(mandelato)borate, exhibited exceptional enantioselective adsorption performance. Thus, the chiral polymeric microcapsules embedded with the R-isomer of the bis(mandelato)borate anion demonstrated significant selectivity for adsorbing L-Trp, yielding a mixture with 70% enantiomeric excess after 96 h. In contrast, microcapsules containing the S-isomer of the bis(mandelato)borate anion preferentially adsorbed D-Trp, achieving an enantiomeric excess of 73% after 48 h. [ABSTRACT FROM AUTHOR]

The present work investigates the failure of a rear axle hypoid gear that failed during fatigue life testing before meeting the criteria. The failure being in contrary to the historical field failure where the mating pinion gear fails as the primary member became critical and hence detailed failure analysis was carried out. Failure analysis involving fractography, magnetic particle inspection, microstructural analysis, hardness tests, scanning electron microscopy, electron discharge spectroscopy was carried out. Meticulous failure analysis revealed that the hypoid gear failed due to the presence of non-metallic inclusion. SEM and EDX analysis further supported the analysis showing aluminum, calcium, magnesium along with oxygen as major constituents. The work also provided recommendations in the form of process modifications at the steel plant to avoid such kind of failures. [ABSTRACT FROM AUTHOR]

[Display omitted] Component selection is crucial for microwave absorbents. Multi-component absorbers are increasingly useful and can be prepared through the rational design and control of various electrical, magnetic, and other auxiliary components. In this paper, Ni 3 Fe/NiFe 2 O 4 nanospheres with two-phase magnetism were designed for use as a multi-component absorber. Specifically, a Ni 3 Fe/ NiFe 2 O 4 @SPC composite with 3D networks was successfully fabricated by hydrothermal method, high-temperature carbonization for activation, and electrostatic self-assembly. The contact interface and coupling effect between the two magnetic components can promote the attenuation of electromagnetic waves. Moreover, the introduction of porous carbon successfully inhibits the easy aggregation of the magnetic particles. Impressively, with a filling load of 10 wt%, the optimal RL of the prepared Ni 3 Fe/NiFe 2 O 4 @SPC composite reaches −60.6 dB, and the effective absorption bandwidth is 5.2 GHz at 2 mm. The combination of two magnetic components and porous carbon in this multiphase microwave-absorbing composite demonstrates a feasible strategy for designing efficient microwave absorbers in the future. [ABSTRACT FROM AUTHOR]

Here, the core-shell structured FeSiBCuNb/Fe 3 O 4 soft magnetic composites (SMCs) were successfully designed and fabricated by coating Fe 3 O 4 magnetic nanoparticles on the surface of phosphorylated FeSiBCuNb powder. The effects of Fe 3 O 4 and Polyvinylpyrrolidone (PVP) contents on the micromorphology, interface structure, and soft magnetic properties of SMCs were systematically investigated. The results demonstrate that the Fe 3 O 4 magnetic nanoparticles are uniformly distributed on the surface of magnetic powders, which fill up the air gap in-between the magnetic powder and increase the resistivity. It shows that the permeability gradually decreases with the increase of Fe 3 O 4 from 0 wt% to 1 wt%, while the loss decreases first and then increases. The loss separation of SMCs indicates that the Fe 3 O 4 nanoparticles effectively reduce the hysteresis loss and eddy current loss. Furthermore, the FeSiBCuNb/Fe 3 O 4 SMCs with the addition of PVP as a binder enhance the binding force between Fe 3 O 4 nanoparticles and the powder matrix, which facilitates the formation of a uniform and dense interface structure. When adding 0.3 wt% PVP + Fe 3 O 4 nanoparticles, the FeSiBCuNb/Fe 3 O 4 SMCs exhibit excellent soft magnetic properties with ultra-low loss of 138.5 kW/m3 (100 mT/50 kHz), high permeability of 54, and good frequency stability. The presented results provide a new strategy for synthesizing ultra-low core loss and frequency stability of core-shell structured SMCs, which has great potential for applications at high frequencies. [ABSTRACT FROM AUTHOR]

There is an urgent need for multifunctional materials that possess high absorption and infrared stealth capabilities to address the increasingly complex and severe electromagnetic pollution. This research explores how the microstructure of components and the design of the absorber impact the stealth performance of electromagnetic and infrared waves. This research involved designing and fabricating a bi-layer sample with a hierarchical structure consisting of FeCoNi magnetic particles as the absorbing layer and Cu 2 O micro-cube/ h -BN nanocomposite as the matching layer. The particular design of the absorber was instrumental in intensifying the synergistic relationship between dielectric and magnetic loss, thereby achieving a superior level of impedance matching and absorption efficacy. The optimized microwave absorption performance was achieved by tuning thickness and arrangement of each layer. It shows that the minimum reflection loss for bilayer sample reaches −38 dB with a total thickness of only 1.2 mm, and effective absorption bandwidth of 4.4 GHz which covers 75 % of the entire ku frequency band. Its excellent electromagnetic and infrared wave stealth performance may be attributed to enhanced heterogeneous interfaces and consequently polarization relaxation along with magnetic loss, which result from multi-component synergy and the unique 3D hierarchical microstructure and interconnection between particles. [ABSTRACT FROM AUTHOR]

In the present paper, the assessment of vortex-assisted dispersive magnetic solid-phase extraction using amino-functionalized mesoporous combined with direct magnetic sorbent sampling (DMSS) in flame or furnace atomic absorption spectrometry (FAAS or FF-AAS) was demonstrated for highly sensitive silver determination in water samples. The developed method showed significant enrichment factors compared to conventional pneumatic nebulization by FAAS, 607 for DMSS-FF-AAS and 114 for DMSS-FAAS. The analytical curve showed linearity in the range from 5.0 to 70.0 µg L− 1 and 1.0 to 15.0 µg L− 1 and limits of detection of 0.59 and 0.09 µg L− 1 for DMSS-FAAS and DMSS-FF-AAS, respectively. The intra and inter-day precision evaluated as a percentage of the relative standard deviation (RSD,%) ranged from 1.89 to 4.71% for levels of 25.0 and 65.0 µg L− 1. The method was applied in different kinds of water samples without matrix effects, yielding recovery values from 90 to 110%. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of particle size on liver R2*$$ {\mathrm{R}}_2^{\ast } $$ by Monte Carlo simulation and phantom studies at both 1.5 T and 3.0 T. Methods: Two kinds of particles (i.e., iron sphere and fat droplet) with varying sizes were considered separately in simulation and phantom studies. MRI signals were synthesized and analyzed for predicting R2*$$ {\mathrm{R}}_2^{\ast } $$, based on simulations by incorporating virtual liver model, particle distribution, magnetic field generation, and proton movement into phase accrual. In the phantom study, iron‐water and fat‐water phantoms were constructed, and each phantom contained 15 separate vials with combinations of five particle concentrations and three particle sizes. R2*$$ {\mathrm{R}}_2^{\ast } $$ measurements in the phantom were made at both 1.5 T and 3.0 T. Finally, differences in R2*$$ {\mathrm{R}}_2^{\ast } $$ predictions or measurements were evaluated across varying particle sizes. Results: In the simulation study, strong linear and positively correlated relationships were observed between R2*$$ {\mathrm{R}}_2^{\ast } $$ predictions and particle concentrations across varying particle sizes and magnetic field strengths (r≥0.988$$ r\ge 0.988 $$). The relationships were affected by iron sphere size (p<0.001$$ p<0.001 $$), where smaller iron sphere size yielded higher predicted R2*$$ {\mathrm{R}}_2^{\ast } $$, whereas fat droplet size had no effect on R2*$$ {\mathrm{R}}_2^{\ast } $$ predictions (p≥0.617$$ p\ge 0.617 $$) for constant total fat concentration. Similarly, the phantom study showed that R2*$$ {\mathrm{R}}_2^{\ast } $$ measurements were relatively sensitive to iron sphere size (p≤0.004$$ p\le 0.004 $$) unlike fat droplet size (p≥0.223$$ p\ge 0.223 $$). Conclusion: Liver R2*$$ {\mathrm{R}}_2^{\ast } $$ is affected by iron sphere size, but is relatively unaffected by fat droplet size. These findings may lead to an improved understanding of the underlying mechanisms of R2*$$ {\mathrm{R}}_2^{\ast } $$ relaxometry in vivo, and enable improved quantitative MRI phantom design. [ABSTRACT FROM AUTHOR]

Magnetic particle imaging (MPI) is an emerging noninvasive molecular imaging modality with high sensitivity and specificity, exceptional linear quantitative ability, and potential for successful applications in clinical settings. Computed tomography (CT) is typically combined with the MPI image to obtain more anatomical information. Herein, a deep learning‐based approach for MPI‐CT image segmentation is presented. The dataset utilized in training the proposed deep learning model is obtained from a transgenic mouse model of breast cancer following administration of indocyanine green (ICG)‐conjugated superparamagnetic iron oxide nanoworms (NWs‐ICG) as the tracer. The NWs‐ICG particles progressively accumulate in tumors due to the enhanced permeability and retention (EPR) effect. The proposed deep learning model exploits the advantages of the multihead attention mechanism and the U‐Net model to perform segmentation on the MPI‐CT images, showing superb results. In addition, the model is characterized with a different number of attention heads to explore the optimal number for our custom MPI‐CT dataset. [ABSTRACT FROM AUTHOR]

Electromagnetic cooperative strategy has been proved to be an effective approach that can significantly decrease the matching thickness required for reflection loss. However, improving the electromagnetic wave (EMW) absorbing effectiveness with low matching thickness remains challenging for current single-phase absorbing materials. A layer-by-layer construction design is used in our study via a combination with iso-butyl isoprene rubber (IIR) and mixed polyurethane (MPU) as the matrix, with the single-wall carbon nanotubes (SWCNTs) and magnetic powder as fillers. This bilayer composite design resulted in a decrease in matching thickness and a shift in absorption bandwidth to higher frequencies by 40 %–50 %. Furthermore, the trilayer structure of MPU/IIR/MPU was found to stabilize permeability, enhance the thermal stability of the magnetism and improve the shielding effectiveness significantly. The thickness corresponding minimum absorption loss of the trilayer composites decreased and the absorption bandwidth of −10 dB widened by 50 % from 8.2 GHz–9.5 GHz to 10.2 GHz–12.4 GHz. [ABSTRACT FROM AUTHOR]

In this study, amino-functionalized magnetic particles (iron oxide@SiO2-NH2) with core-shell structures were synthesized and evaluated for rapid boron removal from aqueous solutions. The results showed that the specific surface area of the iron oxide@SiO2-NH2 (131.24 m2⋅g−1) increased greatly compared to pure iron oxide (30.98 m2⋅g−1). The adsorption equilibrium was less than 2 h, with an adsorption capacity of 29.76 mg⋅g−1 at pH = 6 at 15 °C. The quasi-second-order kinetic model described the boron adsorption process well, and both the Langmuir and Freundlich models were suitable for characterizing the adsorption isotherms. The zeta potential and XPS analysis before and after adsorption revealed that the main adsorption mechanism was the hydrogen bonding formation between the terminal -NH2 groups of the adsorbent and the boric acid. In addition, the adsorbent still maintained a high adsorption performance after five adsorption–desorption cycles, which illustrated that the iron oxide@SiO2-NH2 may be a potential adsorbent for environmental boron removal treatment. [ABSTRACT FROM AUTHOR]

Residual fragments can remain after kidney stone extraction which may necessitate another intervention. A new approach needs to be developedis needed to lower the risk of disease severe side effects caused by these fragments. Magnetic nanoparticles can be applied due to their properties of being able to bind to residual fragments and to be extracted by an external magnetic field. Fractals and magnetic nanoparticles have been synthesized and characterized thoroughly. The small nanoparticles bind covalently to the kidney stones and a magnetic extraction of calcium oxalate fractals with magnetic nanoparticles is possible. The aggregation of nanoscale iron oxide nanoparticles can be induced with the addition of salt which improves the extraction process. The separation is validated by simulation and experimentally in a porcine kidney as well as in artificial kidney models. This proof-of-concept study successfullyis the fundament for a new waydemonstrated of extracting kidney stones extraction and including their fractals and might pave the way for new procedures in urology. [ABSTRACT FROM AUTHOR]

Magnetic reconnection is a fundamental plasma process which facilitates the conversion of magnetic energy to particle energies. This local process both contributes to and is affected by a larger system, being dependent on plasma conditions and transporting energy around the system, such as Earth's magnetosphere. When studying the reconnection process with in situ spacecraft data, it can be difficult to determine where spacecraft are in relation to the reconnection structure. In this work, we use k‐means clustering, an unsupervised machine learning technique, to identify regions in a 2.5‐D PIC simulation of symmetric magnetic reconnection with conditions comparable to those observed in Earth's magnetotail. This allows energy flux densities to be attributed to these regions. The ion enthalpy flux density is the most dominant form of energy flux density in the outflows, agreeing with previous studies. Poynting flux density may be dominant at some points in the outflows and is only half that of the Poynting flux density in the separatrices. The proportion of outflowing particle energy flux decreases as guide field increases. We find that k‐means is beneficial for analyzing data and comparing between simulations and in situ data. This demonstrates an approach which may be applied to large volumes of data to determine statistically different regions within phenomena in simulations and could be extended to in situ observations, applicable to future multi‐point missions. Plain Language Summary: Magnetic reconnection is the change in connectivity of magnetic field lines. The small‐scale physics at the center of reconnection causes conversion of magnetic energy to particle energies. This is important for the impacts on the large‐scale system in which the reconnection takes place, such as Earth's magnetosphere. We use machine learning techniques to identify regions of the structure of the reconnection site. This can be done using only the plasma and field variables, without providing any information on the location. We can look at how energy is shared between the fields and particles in these regions to determine the behavior of the energy conversion across the reconnection site. We find ion energy is the largest output energy, agreeing with previous studies. As the magnetic field perpendicular to the reconnection structure increases, less energy is converted to the particles. This demonstrates that these machine learning techniques may be used to identify regions in plasma phenomena and could be applied to large amounts of data to carry out statistical studies. Key Points: k‐means clustering identifies statistically different regions of a symmetric reconnection site in a 2.5‐D PIC simulationWe confirm that outgoing particle energy fluxes decrease due to increased guide fieldClustering may be applied to large quantities of simulation and in situ data to carry out statistical analysis of plasma phenomena [ABSTRACT FROM AUTHOR]

An alternative method based on cementation for the recovery of nickel from spent Ni/Al2O3 reforming catalyst pregnant leach solution (PLS) was proposed to overcome the limitations of traditional two-step extraction and precipitation processes. Thermodynamic analysis was used to evaluate the potential interference of key reactions, such as nickel and sacrificial metal leaching, with the selective cementation of nickel from the PLS. Key variables in the cementation process were optimized using response surface methodology (RSM) combined with Box–Behnken design (BBD). Under optimal conditions—pH 2.2 ± 0.1, processing time of 15 min, and Al/Ni molar ratio of 2.65—a maximum nickel recovery of 73.2% was achieved. Extensive characterization confirmed the high quality of the cemented nickel product: (i) ICP-OES indicated nickel purity of 99.47%, (ii) XRD patterns verified the presence of pure face-centered cubic nickel, (iii) SEM-EDS and vibrating sample magnetometry confirmed the high purity of the metallic nickel particles. [ABSTRACT FROM AUTHOR]

Context. The particle-in-cell approach has proven effective in modeling neutron-star and black-hole magnetospheres from first principles, but global simulations are plagued with an unrealistically small separation between the scales where microphysics operates and the system-size scales due to limited numerical resources. A legitimate concern is whether the scale separation achieved to date is large enough for results to be safely extrapolated to realistic scales. Aims. In this work, our aim is to explore the effect of scaling up physical parameters and to check whether salient features uncovered by pure kinetic models at smaller scales are still valid, with a special emphasis on particle acceleration and high-energy radiation emitted beyond the light cylinder. Methods. To reach this objective, we developed a new hybrid numerical scheme coupling the ideal force-free and the particle-in-cell methods to optimize the numerical cost of global models. We propose a domain decomposition of the magnetosphere based on the magnetic-field topology using the flux function. The force-free model is enforced along open field lines while the particle-in-cell model is restricted to the reconnecting field line region. Results. As a proof of concept, this new hybrid model is applied to simulate a weak millisecond pulsar magnetosphere with realistic scales using high-resolution axisymmetric simulations. Magnetospheric features reported by previous kinetic models are recovered, and strong synchrotron radiation above 100MeV consistent with the Fermi-LAT gamma-ray pulsar population is successfully reproduced. Conclusions.This work further consolidates the shining-reconnecting current sheet scenario as the origin of the gamma-ray emission in pulsars, as well as firmly establishing pulsar magnetospheres as at least teraelectronvolt particle accelerators. [ABSTRACT FROM AUTHOR]

Magnetic ionic liquids (MILs) are a subclass of ionic liquids that exhibit paramagnetic properties intrinsically, without the need for additional magnetic particles. These properties can be attributed to the cations, anions, or both. Typically, MILs incorporate transition or inner‐transition metals within the anion structure. These adaptable liquids demonstrate remarkable physicochemical properties, notably a robust response to external magnetic fields. The body of research concerning the synthesis, characterization, and practical applications of MILs has expanded swiftly in recent times. This review delves into the latest research on the synthesis, properties, and utilization of MILs across various domains, including catalysis, fluid‐fluid separation, polymer science, and analytical chemistry. Within the realm of analytical chemistry, MILs are pivotal, serving as solvents in various analytical procedures such as dispersive liquid‐liquid micro‐extraction, matrix solid‐phase dispersion, and single‐drop micro‐extraction. Owing to their paramagnetic nature, MILs are instrumental in the separation process, streamlining organic reactions by obviating the need for traditional extraction or centrifugation steps. [ABSTRACT FROM AUTHOR]

Metal-bonded magnetic composites (MBMCs) present a promising alternative to dense sintered magnets, particularly for intricate components. Compared to polymer-based bonded magnets, MBMCs have wider applicability in harsh environments. In this paper, we demonstrate a solid-state shear-based manufacturing technique to introduce localized magnetization into a paramagnetic aluminum matrix by embedding SmCo5 permanent magnet particles. Our magnetic composites display hard magnetic behavior with a coercivity of 13 kOe and a remanent magnetization of 4.32 emu/g. In addition to magnetization, we also report a 9% improvement in Young's modulus. Despite the local temperature rise during processing, the magnetic phases didn't decompose into unwanted phases, preserving the composite's hard magnetic properties. Creation of an interfacial metallurgical bond with the matrix ensured the suitability of the composites for structural applications. Our study investigates the mechanical, and functional properties of composites, paving the way for lightweight structural magnetic composites with a transformative potential in the aerospace, nuclear, and automotive applications. This work underscores the potential for further optimization and development to drive innovations in magnet and equipment design. [ABSTRACT FROM AUTHOR]

Fabrication of architected materials through self‐assembly of units offers many advantages over monolithic solids including recyclability, reconfigurability, self‐healing, and diversity of emergent properties – all prescribed chiefly by the choice of the building blocks. While self‐assembly is prevalent in biosynthesis, it remains challenging to recapitulate it macroscopically. Recent success in the self‐assembly of 2D ordered open magneto‐elastic lattices from centimeter‐long bar units with sticky magnetic ends, showcasing graceful failure at “magnetic bonds” and re‐assembly under extreme loading. However, it is still unclear how this approach can be generalized to design units that preferably form ordered low‐energy structures with desirable mechanical properties such as ductility, auxetics, and impact resistance. Here, diverse ordered 2D lattice structures are predicted as the self‐assembly outcomes from units with 2 (bar), 3 (Y‐shape), and 4 (cross) branches with magnetic ends. The defect formation is significantly reduced by a computational design approach. Tunable mechanical behavior is shown to be achieved by varying unit shapes and magnet orientations. Cross‐shaped units are identified for their promise in auxetic response and penetration resistance with these findings validated through experiments. The work highlights the potential of self‐assembling magnetic architected materials for adaptive structures, impact mitigation, and energy adsorption. [ABSTRACT FROM AUTHOR]

We have performed a comparative computational study of magnetic particle alignment in a strong magnetic field and ambient viscous fluid using the first-principles Navier–Stokes equation as well as numerical modeling using the finite element method (FEM). FEM solution has been compared with the solution of the unsteady rotations of a magnetic particle in a viscous fluid during the alignment process described with nonlocal integro-differential equations (IDEs) for torque and angular velocity. The assumption of nonlocality comes from the history term of acceleration torque with a non-Basset kernel function, which has its origin in the presence of vortices in the flow of a particle fluid environment due to its unsteady rotation and ambient fluid inertia and friction. The flow vortices of the ambient fluid are explicitly shown in the solution of the FEM model. Moreover, the solution of the time evolution of the alignment angle and angular velocity for the FEM model are in good agreement with an IDE model which we have recently developed. The obtained results are justification for interchangeability of the FEM and IDE models, which may have important consequences for large-scale simulations of magnetic microparticles. [ABSTRACT FROM AUTHOR]

Reconfigurability within hydrogels has emerged as an attractive functionality that can be used in information encryption, cargo/delivery, environmental remediation, soft robotics, and medicine. Here micro‐patterned polymer hydrogels capable of temperature‐dependent reconfigurability are fabricated. For this, the hydrogels are provided with micron‐sized Pickering emulsion droplets stabilized by magnetic particles, which are capable of harnessing energy from external force fields. The droplets can both migrate under magnetic field gradients and heat the environment when laser irradiated. These functions not only affect a single compartment but have higher‐order effects on the mesoscale, thanks to the temperature‐responsiveness of the polymeric network. This double responsiveness is exploited to control the spatial organization of hundreds of droplets within the hydrogel matrix and form predesigned and sophisticated patterns. Furthermore, pattern self‐reconfiguration driven by the droplets themselves upon laser irradiation is induced. Finally, we show that due to their internal liquid phase, the droplets can be used as reservoirs of hydrophobic nutrients for living cells (i.e., Yarrowia lipolytica yeast) in the solid‐like environment of the polymeric network, and demonstrate communication between the droplets and the cells to facilitate nutrient uptake. Altogether, the results provide opportunities for the development of stimuli‐sensitive polymer hydrogels with post‐synthesis reprogrammable response using micro‐compartments as building blocks. [ABSTRACT FROM AUTHOR]

Viscous remanent magnetization (VRM) in multidomain (MD) particles has many puzzling properties that deviate from the current VRM theory, based on Néel's single‐domain model of magnetic particles with an almost symmetric double‐well potential. In larger magnetic particles experimental evidence indicates that more complex magnetization structures preferentially change from high‐energy states to low‐energy states with large energy differences, such that VRM is preferentially acquired by directed magnetization changes in strongly asymmetric double‐well potentials. Here, a statistical model based on this 'trapdoor' VRM (tdVRM) naturally explains the experimental observations of initial‐state dependence, time‐lag variation, non‐linear logt $\log \,t$ dependence, and acquisition‐decay asymmetry for MD VRM. It is discussed how tdVRM can be experimentally distinguished from single‐domain VRM and how the new theory can help to improve age determination by VRM analysis. Plain Language Summary: The magnetization of rocks is an important property used to determine the history of the Earth surface and variations of Earth's magnetic field. Magnetite particles in rocks are abundant recorders of this field, and particles larger than about 500 nm in diameter are called multidomain (MD) magnetites. If a rock, after its formation, lies at Earth's surface for a long time, its magnetization slowly changes—the newly acquired remanent magnetization is called a viscous remanent magnetization (VRM). This VRM is well understood for magnetite particles below about 150 nm in diameter, but no comprehensive theory so far explains all its experimentally observed properties. Here a statistical model is developed that can explain the experimental facts and helps to understand their physical origin. The new theory allows theoretical investigation of different methods to determine the amount of time a rock was exposed to Earth's present‐day magnetic field. This leads to a better understanding of time‐temperature relations for VRM, and improves the determination of relocation ages based on VRM. Key Points: Multidomain viscous remanent magnetization (MD VRM) is dominated by decay into trapdoor potential minimaPreviously inexplicable properties of MD VRM are explained by a quantitative trapdoor VRM theoryTrapdoor VRM suggests an improved method for VRM age determination [ABSTRACT FROM AUTHOR]

Magnetorheological fluid and their properties are essential in Magnetorheological applications. The present study aims to obtain the thermally stable carrier fluid for Magnetorheological damper application through thermogravimetric analyses of three base fluids for higher stability fluid to synthesize Magnetorheological fluid. Scanning electron microscopic images of particles were also tested for their morphology. Magnetorheological fluid samples with 10%, 15%, and 20% by volume were prepared in-house with a 3% calcium base additive (base fluid). Sedimentation and thermal conductivity studies reveal that increasing particle concentration increases the settling time and thermal conductivity. The flow properties show an increase in yield stress with an increase in particle concentration and magnetic fields. The application part of the fluid consists of Magnetorheological damper fabrication and dynamic testing of 20% volume concentration particles at 10 mm amplitude, 2 Hertz frequency, and 0 Ampere and 0.5 Ampere currents, and the temperature of the system is captured with a K-type thermocouple. The results show an 8.2 °C rise at 0.5 Ampere with a 26.2% force decrease within 1000 cycles. The theoretical model based on the lumped parameter analysis predicts the temperature rise, similar to the experimental analysis with a 9.5% error. [ABSTRACT FROM AUTHOR]

The Ti-6Al-4V alloy is an important material used in many high-end devices, such as medical, aerospace, petrochemical, and sports equipment. Thus, the feasibility of producing Ti-6Al-4V with mirror surface quality through magnetic polishing was assessed in this study. One of the extremely challenging aspects of magnetic polishing for Ti-6Al-4V alloys is the generation of a magnetic field suitable for surface-quality finishing. Moreover, machined material residue cannot be completely removed, the alloy has limited application, and uniform surface quality on a large workpiece surface cannot be achieved because generating strong and suitable magnetic field is currently infeasible. To create a polishing process with a highly efficient magnetic field source for improving material removal rate and surface quality, a linear variable magnetic field array was proposed by Halbach. Finite element simulation processes combined with experimental validation provide an efficient polishing model with high field area and intensity generated by an improved Halbach magnet array. The magnetic force generated by the improved Halbach array and the force distribution process on the Fe3O4 magnetic particle were analyzed. Thus, material removal and the distribution and pressure of abrasive SiO2 particles acting on the polished surface were examined. The influences of technological factors on surface quality and material removal ability were systematically studied. The proposed chemical–magnetorheological finishing model showed a considerably increased magnetic field generation compared with the previous model (1.7 times that of the conventional Halbach array), thereby efficiently removing materials. Polishing models established for Ti-6Al-4V alloy markedly improved surface quality after 80 min of treatment, and an ultrafine workpiece surface showed an Ra of 1 nm, which had an initial roughness of approximately 500 nm. [ABSTRACT FROM AUTHOR]

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Metropolitan Mexico City (MMC) children and young adults exhibit overlapping Alzheimer and Parkinsons' diseases (AD, PD) and TAR DNA-binding protein 43 pathology with magnetic ultrafine particulate matter (UFPM) and industrial nanoparticles (NPs). We studied magnetophoresis, electron microscopy and energy-dispersive X-ray spectrometry in 203 brain samples from 14 children, 27 adults, and 27 ALS cases/controls. Saturation isothermal remanent magnetization (SIRM), capturing magnetically unstable FeNPs ~ 20nm, was higher in caudate, thalamus, hippocampus, putamen, and motor regions with subcortical vs. cortical higher SIRM in MMC = 40y. Motion behavior was associated with magnetic exposures 25-100 mT and children exhibited IRM saturated curves at 50-300 mT associated to change in NPs position and/or orientation in situ. Targeted magnetic profiles moving under AC/AD magnetic fields could distinguish ALS vs. controls. Motor neuron magnetic NPs accumulation potentially interferes with action potentials, ion channels, nuclear pores and enhances the membrane insertion process when coated with lipopolysaccharides. TEM and EDX showed 7-20 nm NP Fe, Ti, Co, Ni, V, Hg, W, Al, Zn, Ag, Si, S, Br, Ce, La, and Pr in abnormal neural and vascular organelles. Brain accumulation of magnetic unstable particles start in childhood and cytotoxic, hyperthermia, free radical formation, and NPs motion associated to 30-50 μT (DC magnetic fields) are critical given ubiquitous electric and magnetic fields exposures could induce motion behavior and neural damage. Magnetic UFPM/NPs are a fatal brain cargo in children's brains, and a preventable AD, PD, FTLD, ALS environmental threat. Billions of people are at risk. We are clearly poisoning ourselves. [ABSTRACT FROM AUTHOR]