Journal articles: 'Magnetic particles'

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Xu, Zhiqiang, Heng Wu, Qiuliang Wang, Liyin Yi, and Jun Wang. "Simulation Study on the Motion of Magnetic Particles in Silicone Rubber-Based Magnetorheological Elastomers." Mathematical Problems in Engineering 2019 (July 18, 2019): 1–11. http://dx.doi.org/10.1155/2019/8182651.

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Magnetorheological elastomer (MRE) is an intelligent composite material and has been widely used in various fields such as vibration reduction and sensing. MRE has an excellent magnetorheological effect through the chaining of its internal magnetic particles. Current studies on MREs mainly focus on the preparation of materials and characterization of mechanical properties. However, very few studies have been conducted on the mechanism of magnetic particle motion during MRE curing. Based on the silicone rubber-based MRE, the motion mechanism of magnetic particles during curing was explored through numerical simulation. First, we analyzed the magnetic force and viscous force of magnetic particles in MRE and discussed the equations of motion of magnetic particles under applied magnetic field. Further, we established a uniform magnetic field model through the finite element method and simulated the motion of two magnetic particles under the magnetic field. Finally, we discussed the effects of particle distribution angles, particle radii, applied magnetic field strength, and distance between particles on particle velocity and displacement. The results show that the distance between particles has the greatest influence on the motion of magnetic particles, and the size of the distance between particles will affect the contact time of the particles, thus affecting the chain formation of magnetic particles in the MRE.

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Farsi, Chouki, Salah Amroune, Mustafa Moussaoui, Barhm Mohamad, and Houria Benkherbache. "High-Gradient Magnetic Separation Method for Weakly Magnetic Particles: an Industrial Application." METALLOFIZIKA I NOVEISHIE TEKHNOLOGII 41, no. 8 (October 25, 2019): 1103–19. http://dx.doi.org/10.15407/mfint.41.08.1103.

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LI, X. L., K. L. YAO, and Z. L. LIU. "CLUSTER MOVING MONTE CARLO SIMULATION OF NANO-SIZED MAGNETIC PARTICLE AGGREGATION IN AN APPLIED MAGNETIC FIELD." International Journal of Modern Physics B 23, no. 27 (October 30, 2009): 5307–23. http://dx.doi.org/10.1142/s0217979209053230.

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We used the cluster moving Metropolis Monte Carlo method combined with image and statistical analyses to simulate magnetized magnetic particle (or magnetic carried particle) aggregation in a uniform magnetic field. Once the particles aggregate together they permanently attach to one another. The dynamics of aggregation is characterized in terms of mean particle size, fractal dimensions, distribution of orientations and radial distribution function for different sized particles. From small to large diameters, the distribution of orientations gradually approaches the orientation of the magnetic field, the larger particles forming chain-like clusters, the smaller ones forming clusters with branched and looped shapes. The fractal dimensions of each diameter indicate fluctuations of 20, 40 and 100 nm during the process. For the polydisperse system, the radial distribution function shows that the peaks shift by integer multiples of the average diameter. This indicates that particles larger than average are the most common to be found forming clusters; the behavior of small particles is not the main factor in cluster formation because they generally attach themselves to the larger-particle clusters. The evolution of the aggregation as a whole can help to analyze the particle configuration in the magnetic separation and magnetic targeting process.

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Ido, Yasushi, Keisuke Asakura, and Hitoshi Nishida. "Behavior of both Nonmagnetic Particles and Magnetic Particles in Magnetic Compound Fluids in a Micro-Tube with Axial Flow under Rotating Magnetic Field." Materials Science Forum 856 (May 2016): 9–14. http://dx.doi.org/10.4028/www.scientific.net/msf.856.9.

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Behaviors of both micrometer-size nonmagnetic abrasive particles and micrometer-size magnetic particles in a magnetic fluid are investigated by using the discrete particle method which is based on the simplified Stokes dynamics. Sheet-like clusters of nonmagnetic particles and sheet-like clusters of magnetic particles alternately appear one after another in the axis direction when the flow velocity is small.

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Peng, Xiao Ling, Hai Biao Wei, Xiao Yang, Rui Ping Yue, and Hong Liang Ge. "Influence of the Magnetic Interaction among Particles on Distributions of Magnetic Fluids Using Computer Simulations." Advanced Materials Research 150-151 (October 2010): 1595–98. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.1595.

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Magnetic fluid is a stable colloidal dispersion of ferromagnetic particles in a liquid carrier. Once a magnetic field is applied to magnetic fluids (MF), various structures of MF are formed. A detailed understanding of structures and particle distributions in gradient magnetic fields is much important. But very few works have been done on this. In the present study, the effects of magnetic field gradient and magnetic interaction among magnetic particles on the structures of MF are investigated using a two-dimensional Monte Carlo simulation. The results show that a gradient distribution of magnetic particles is formed under gradient magnetic fields. However, as the interaction between magnetic particles increases, the distribution gradient decreases, accompanied by the formation of chain-like clusters. Moreover, with increasing the magnetic interaction, particle distribution changes from grass-like clusters to needle-like ones.

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Xia, Q., and V. Zharkova. "Particle acceleration in coalescent and squashed magnetic islands." Astronomy & Astrophysics 635 (March 2020): A116. http://dx.doi.org/10.1051/0004-6361/201936420.

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Aims. Particles are known to have efficient acceleration in reconnecting current sheets with multiple magnetic islands that are formed during a reconnection process. Using the test-particle approach, the recent investigation of particle dynamics in 3D magnetic islands, or current sheets with multiple X- and O-null points revealed that the particle energy gains are higher in squashed magnetic islands than in coalescent ones. However, this approach did not factor in the ambient plasma feedback to the presence of accelerated particles, which affects their distributions within the acceleration region. Methods. In the current paper, we use the particle-in-cell (PIC) approach to investigate further particle acceleration in 3D Harris-type reconnecting current sheets with coalescent (merging) and squashed (contracting) magnetic islands with different magnetic field topologies, ambient densities ranging between 108 − 1012 m−3, proton-to-electron mass ratios, and island aspect ratios. Results. In current sheets with single or multiple X-nullpoints, accelerated particles of opposite charges are separated and ejected into the opposite semiplanes from the current sheet midplane, generating a strong polarisation electric field across a current sheet. Particles of the same charge form two populations: transit and bounced particles, each with very different energy and asymmetric pitch-angle distributions, which can be distinguished from observations. In some cases, the difference in energy gains by transit and bounced particles leads to turbulence generated by Buneman instability. In magnetic island topology, the different reconnection electric fields in squashed and coalescent islands impose different particle drift motions. This makes particle acceleration more efficient in squashed magnetic islands than in coalescent ones. The spectral indices of electron energy spectra are ∼ − 4.2 for coalescent and ∼ − 4.0 for squashed islands, which are lower than reported from the test-particle approach. The particles accelerated in magnetic islands are found trapped in the midplane of squashed islands, and shifted as clouds towards the X-nullpoints in coalescent ones. Conclusions. In reconnecting current sheets with multiple X- and O-nullpoints, particles are found accelerated on a much shorter spatial scale and gaining higher energies than near a single X-nullpoint. The distinct density and pitch-angle distributions of particles with high and low energy detected with the PIC approach can help to distinguish the observational features of accelerated particles.

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Jia, Ran, Biao Ma, Changsong Zheng, Liyong Wang, Xin Ba, Qiu Du, and Kai Wang. "Magnetic Properties of Ferromagnetic Particles under Alternating Magnetic Fields: Focus on Particle Detection Sensor Applications." Sensors 18, no. 12 (November 26, 2018): 4144. http://dx.doi.org/10.3390/s18124144.

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The electromagnetic wear particles detection sensor has been widely studied due to its ability to monitor the wear status of equipment in real time. To precisely estimate the change of the magnetic energy of the sensor coil caused by the wear particles, the magnetic property models of wear particles under the alternating magnetic field was established. The models consider the hysteresis effect and the eddy current effect of the wear particles. The analysis and experimental results show that with the increase of the effective field frequency, the change of the magnetic energy caused by the wear particles gradually decrease, which makes the induced electromotive force output by the sensor reduce with the decrease of the particle speed, so a signal compensation method is presented to obtain a unified signal when the same wear particle passing through the sensor in different speeds. The magnetic coupling effect between the two adjacent wear particles is analyzed. The result illustrates that the change of the magnetic energy caused by the dual wear particles system is larger than the sum of the energy variation caused by two independent wear particles, and with the increase of the interparticle distance, the magnetic coupling effect gradually weakens and disappears.

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Nyang’au, Wilson Ombati, Tamara Kahmann, Thilo Viereck, and Erwin Peiner. "MEMS-Based Cantilever Sensor for Simultaneous Measurement of Mass and Magnetic Moment of Magnetic Particles." Chemosensors 9, no. 8 (August 4, 2021): 207. http://dx.doi.org/10.3390/chemosensors9080207.

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This study presents a measurement approach suitable for the simultaneous determination of both the mass mp and magnetic moment µp of magnetic particles deposited on a micro electro mechanical system (MEMS) resonant cantilever balance, which is operated in parallel to an external magnetic field-induced force gradient F′(z). Magnetic induction B(z) and its second spatial derivative δ2B/δz2 is realized, beforehand, through the finite element method magnetics (FEMM) simulation with a pair of neodymium permanent magnets configured in a face-to-face arrangement. Typically, the magnets are mounted in a magnet holder assembly designed and fabricated in-house. The resulting F′ lowers the calibrated intrinsic stiffness k0 of the cantilever to k0-F′, which can, thus, be obtained from a measured resonance frequency shift of the cantilever. The magnetic moment µp per deposited particle is determined by dividing F′ by δ2B/δz2 and the number of the attached monodisperse particles given by the mass-induced frequency shift of the cantilever. For the plain iron oxide particles (250 nm) and the magnetic polystyrene particles (2 µm), we yield µp of 0.8 to 1.5 fA m2 and 11 to 19 fA m2 compared to 2 fA m2 and 33 fA m2 nominal values, respectively.

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Liberti, Paul, and Maria A. Pino. "5597531 Resuspendable coated magnetic particles and stable magnetic particle suspensions." Magnetic Resonance Imaging 15, no. 5 (January 1997): IX. http://dx.doi.org/10.1016/s0730-725x(97)89732-9.

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Santos da Silva, Safire Torres, Nikola Jerance, and Harijaona Lalao Rakotoarison. "Simulating metallic contamination in permanent magnets used in magnetic sensors." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 38, no. 5 (September 2, 2019): 1683–95. http://dx.doi.org/10.1108/compel-12-2018-0515.

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Purpose The purpose of this paper is to provide a model for simulating contamination by ferromagnetic particles in sensors that use permanent magnets. This topic is especially important for automotive applications, where magnetic sensors are extensively used and where metallic particles are present, particularly because of friction between mechanical parts. The aim of the model is to predict the particle accumulation and its effect on the sensor performance. Design/methodology/approach Magnetostatic moment method is used to calculate particles' magnetization and magnetic field. Magnetic saturation is included and Newton–Raphson method is used to solve the non-linear system. Magnetic force on particles is calculated as a gradient of energy. Dynamic simulation provides the positions of agglomerated particles. Findings A simulation of magnetic park lock sensor shows a significant impact of ferromagnetic particles on sensor's accuracy. Moreover, gains on computational time because of model optimizations are reported. Research limitations/implications Only magnetic force and gravity are taken into account for particle dynamics. Mechanical forces such as friction and particle interactions might be considered in future works. Practical implications This paper provides the possibility to evaluate and improve magnetic sensor design with respect to particles contamination. Originality/value The paper presents a novel simulation tool developed to answer the growing need for reliable and fast prediction of magnetic position sensors’ degradation in the presence of metallic particles.

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Abedini-Nassab, Roozbeh, and Ali Emamgholizadeh. "Controlled Transport of Magnetic Particles and Cells Using C-Shaped Magnetic Thin Films in Microfluidic Chips." Micromachines 13, no. 12 (December 8, 2022): 2177. http://dx.doi.org/10.3390/mi13122177.

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Single-cell analysis is an emerging discipline that has shown a transformative impact in cell biology in the last decade. Progress in this field requires systems capable of accurately moving the cells and particles in a controlled manner. Here, we present a microfluidic platform equipped with C-shaped magnetic thin films to precisely transport magnetic particles in a tri-axial rotating magnetic field. This innovative system, compared to the other rivals, offers numerous advantages. The magnetic particles repel each other to prevent undesired cluster formation. Many particles move synced with the external rotating magnetic field, which results in highly parallel controlled particle transport. We show that the particle transport in this system is analogous to electron transport and Ohm’s law in electrical circuits. The proposed magnetic transport pattern is carefully studied using both simulations and experiments for various parameters, including the magnetic field characteristics, particle size, and gap size in the design. We demonstrate the appropriate transport of both magnetic beads and magnetized living cells. We also show a pilot mRNA-capturing experiment with barcode-carrying magnetic beads. The introduced chip offers fundamental potential applications in the fields of single-cell biology and bioengineering.

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Boyajian, Taline, Didier Vincent, Martine Le Berre, and Sophie Neveu. "Magnetic Behavior of Barium Hexaferrite Nanoparticles." Advanced Materials Research 324 (August 2011): 286–89. http://dx.doi.org/10.4028/www.scientific.net/amr.324.286.

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An analysis of the magnetic behavior of Barium Hexaferrite nanoparticles is presented in this paper. The particles’ average size is around 200 nm. The SU-8 photoresist is used as dielectric host matrix in which the particles are embedded. The volume fraction of magnetic particles reached is around 10%. Microwave characterizations show the properties of the resulting nanocomposite. The external applied magnetic field plays the main role in orienting these magnetic particles in the composite. Coplanar CPW lines were used to investigate the magnetic material’s efficiency by its non-reciprocal effects. Magnetic nanocomposites seem promising material for future applications. Thus, higher magnetic particle volume fractions and better orientation are required.

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Parekh, Kinnari, R. V. Upadhyay, and V. K. Aswal. "Monodispersed Magnetic Fluids: Synthesis and Characterization." Solid State Phenomena 155 (May 2009): 155–62. http://dx.doi.org/10.4028/www.scientific.net/ssp.155.155.

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Magnetite and Co ferrite particles were synthesized with control of particle size distribution via non-aqueous route. The XRD pattern shows the formation of single phase spinel structure with the particle size of 96 Å and 80 Å respectively for magnetite and cobalt ferrite. TEM image of the same shows the particles are nearly spherical with the size matches with that obtained from X-ray and the size distribution is less than 5%. Magnetic measurement also shows the particles of uniform size with high value of saturation magnetization at room temperature compared to that obtained by other route. SANS study confirms our results of monodispersed particles with spherical shape.

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Uyeda, Chiaki, Keiji Hisayoshi, and Kentaro Terada. "Separation of Particles Composed of a Solid Solution [Mg₂SiO₄ -Fe₂SiO₄] in the Sequence of Fe²⁺ Concentration Using a Pocketsize Magnetic-Circuit." Key Engineering Materials 843 (May 2020): 105–9. http://dx.doi.org/10.4028/www.scientific.net/kem.843.105.

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Magentic separation generally required strong magnetic forces induced in ferromagnetic or strong paramagnetic particles; in order to realize the separation in diamagnetic or weak paramagnetic particles, it was necessary to attach magnetic beads or magnetic ions to induce the strong magnetic force. A method to separate mixture of weak magnetic particles by its concentration of paramagnetic ferrous ion is newly proposed, which does not require the abovementioned magnetic attachments. The efficiently of the new method is experimentally examined using a pocketsize magnetic circuit (4.5 cm x2.0 cm x 1.0 cm) and a piece of cross sectional paper (5.0 cm x1.0cm). The separation is based on a principle that velocity of a translating particle, induced by a magnetic volume force in an area of monotonically decreasing field, is uniquely determined only by its magnetic susceptibility (per unit mass) of the particle; the velocity is independent to mass of particle. By examining the spectra of the separated particles recovered on the cross sectional paper, a histogram on Fe concentration is easily obtained for the particles without the need of consuming them.

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Yulia, Wita, and Erwin Erwin. "ANALISIS SIFAT MAGNETIK DAN STRUKTUR PARTIKEL PASIR BESI PANTAI ARTA PARIAMAN SUMATERA BARAT MENGGUNAKAN BALL MILLING." Komunikasi Fisika Indonesia 16, no. 2 (October 31, 2019): 107. http://dx.doi.org/10.31258/jkfi.16.2.107-112.

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Analisys of magnetic properties and structure of particles of iron sand of Arta, Pariaman beach West Sumatra. Has been conducted the iron sand samples were dried, then the iron sand separation process was carried out using Iron Sand Separator (ISS). Next, the sample was milled for 30, 60 and 90 hours. The separation between magnetic particles and non magnetic particles was done using Neodymium Iron Boron (NdFeB) magnet. Magnetic induction measurements were carried out using Pasco PS-2162 Magnetic Probe which measured the total magnetic induction of solenoid (solenoid with core sample and milled sample(consentrate II)) as a function of electric current of 1-8 A for a fixed distance of 1 mm. Identification of the content of elements contained in iron sand before and after processing with Ball Milling for 90 hours was carried out using X-Ray Fluorescence (XRF). The phase of magnetic particles processed by Ball Milling was determined using X-Ray Diffraction (XRD). The calculation results show that the magnetic susceptibility of the sample increases with increasing Ball Milling time, from (69426,19 × 10-5 – 80332,13 × 10-5). These values are in the interval 220 - 380.000 × 10-5of the Ilmenite mineral. The magnetite phase appears more than the maghemite phase and the hematite phase after Ball Milling for 90 hours. The particle size of magnetik particle decreases as milling time increase, this trend is confirmed by the result of XRD.

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Johnson, Grant, Patrick Kilian, Fan Guo, and Xiaocan Li. "Particle Acceleration in Magnetic Reconnection with Ad Hoc Pitch-angle Scattering." Astrophysical Journal 933, no. 1 (July 1, 2022): 73. http://dx.doi.org/10.3847/1538-4357/ac7143.

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Abstract Particle acceleration during magnetic reconnection is a long-standing topic in space, solar, and astrophysical plasmas. Recent 3D particle-in-cell simulations of magnetic reconnection show that particles can leave flux ropes due to 3D field-line chaos, allowing particles to access additional acceleration sites, gain more energy through Fermi acceleration, and develop a power-law energy distribution. This 3D effect does not exist in traditional 2D simulations, where particles are artificially confined to magnetic islands due to their restricted motions across field lines. Full 3D simulations, however, are prohibitively expensive for most studies. Here, we attempt to reproduce 3D results in 2D simulations by introducing ad hoc pitch-angle scattering to a small fraction of the particles. We show that scattered particles are able to transport out of 2D islands and achieve more efficient Fermi acceleration, leading to a significant increase of energetic particle flux. We also study how the scattering frequency influences the nonthermal particle spectra. This study helps achieve a complete picture of particle acceleration in magnetic reconnection.

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Hu, Da Wei, and Yan Ming Wang. "Preparation of Hexagonal Fe₃O₄ Nanometer Particles via Weakly Magnetic Field Assisted Oxidation Co-Precipitation." Advanced Materials Research 418-420 (December 2011): 286–92. http://dx.doi.org/10.4028/www.scientific.net/amr.418-420.286.

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This paper utilized a novel oxidative co-precipitation method to synthesis hexagonal Fe3O4 nanometer particles, which assisted by a weakly magnetic field. The crystallinity, morphology, particle size distribution, compositions and magnetic properties of the as-prepared particles were investigated using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), ultrasonic particle sizer (UPS), X-ray photoelectron spectra (XPS) and vibrating sample magnetometer (VSM). The formation mechanism of the hexagonal Fe3O4 nanometer particles, which assisted by a weakly magnetic field was also discussed. The results shown that the as-prepared hexagonal particles were purity magnetite (Fe3O4), and the weakly magnetic field could accelerate the phase transformation from goethite (α-FeOOH) to magnetite (Fe3O4), increase the particle size and uniform the morphology. The values of saturation magnetization (Ms) and coercivity (H) of the hexagonal magnetic particles are 71.05 emu•g-1 and 474.3 Oe, respectively, which contributed to the morphology anisotropy of the particles.

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Ido, Yasushi, Takaya Yamaguchi, and Hitoshi Nishida. "Numerical Analysis of the Polishing Process of Inner Tube Wall Using Micron-Size Particles in Magnetic Fluids." Materials Science Forum 670 (December 2010): 110–17. http://dx.doi.org/10.4028/www.scientific.net/msf.670.110.

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Distribution and behaviour of micron-size magnetic particles and nonmagnetic particles in magnetic fluids in the polishing process of inner wall of small tube is investigated numerically by using the particle method based on the simplified Stokes dynamics. In this study, it is shown that chain-like clusters of both magnetic particles and those of nonmagnetic abrasive particles are formed between the two magnetic poles. The clusters are strongly held during the polishing process. The clusters of the nonmagnetic abrasive particles are surrounding the clusters of magnetic particles and they are combined with each other.

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Ozaki, Masataka. "Preparation and Properties of Well-Defined Magnetic Particles." MRS Bulletin 14, no. 12 (December 1989): 35–40. http://dx.doi.org/10.1557/s0883769400060942.

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Magnetic particles are important not only in the technology, but also in the function of some biosystems. In addition, they are of great scientific interest in developing a better understanding of magnetic phenomena. Ever since magnetic recording media were first prepared, extensive efforts have been made to produce improved magnetic dispersions. The particle s for magnetic media must be of single domain, high saturation magnetization, and proper coercive force. However, the magnetic interactions between such particles are very strong, and stable dispersions are difficult to obtain. Originally, their use was limited to audio tapes, but presently they are employed in a variety of applications. Thus, small particles of different magnetic properties are constituents of magnetic fluids.In 1975, magnetic particles were identified in the bodies of some bacteria, which can navigate along geomagnetic fields. It is also believed that certain animais have the ability to detect a magnetic field due to the presence of magnetic particles in their cells.Techniques are being developed to introduce new functions to materials by incorporating magnetic particles. For example, magnetic particles that are encapsulated by nonmagnetic compounds (e.g. polymers) or particles are used for binding and separating enzymes from reactant mixtures. Efforts are under way to use magnetic particles in drug delivery Systems and for diagnosis.

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Coene, Annelies, and Jonathan Leliaert. "Simultaneous Coercivity and Size Determination of Magnetic Nanoparticles." Sensors 20, no. 14 (July 12, 2020): 3882. http://dx.doi.org/10.3390/s20143882.

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Magnetic nanoparticles are increasingly employed in biomedical applications such as disease detection and tumor treatment. To ensure a safe and efficient operation of these applications, a noninvasive and accurate characterization of the particles is required. In this work, a magnetic characterization technique is presented in which the particles are excited by specific pulsed time-varying magnetic fields. This way, we can selectively excite nanoparticles of a given size so that the resulting measurement gives direct information on the size distribution without the need for any a priori assumptions or complex postprocessing procedures to decompose the measurement signal. This contrasts state-of-the-art magnetic characterization techniques. The possibility to selectively excite certain particle types opens up perspectives in “multicolor” particle imaging, where different particle types need to be imaged independently within one sample. Moreover, the presented methodology allows one to simultaneously determine the size-dependent coercivity of the particles. This is not only a valuable structure–property relation from a fundamental point of view, it is also practically relevant to optimize applications like magnetic particle hyperthermia. We numerically demonstrate that the novel characterization technique can accurately reconstruct several particle size distributions and is able to retrieve the coercivity–size relation of the particles. The developed technique advances current magnetic nanoparticle characterization possibilities and opens up exciting pathways for biomedical applications and particle imaging procedures.

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Parmar, Mayur, Hiral Virpura, and Rajesh Patel. "Large Magnetoviscous Effect in Magnetic and Non Magnetic Ferrodispersion." Solid State Phenomena 209 (November 2013): 78–81. http://dx.doi.org/10.4028/www.scientific.net/ssp.209.78.

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Under the application of magnetic field, magnetic fluids exhibits magnetoviscous effect. We have observed large magneto viscous effects by dispersing magnetic and non-magnetic anisotropic micron size magnetic particles in a ferrofluid , the mixture is known as ferrodispersion. For both the samples density and volume concentrations of large particles are kept identical i.e. 25, 50 and 75 vol %. It is observed that for 25% and 50% vol. concentration the magnetoviscous effect for both the samples is comparable, however for 75% concentration the field dependent viscosity of non-magnetic bentonite anisotropic particles are much larger than its counterpart. This shows even non magnetic particle can also enhance the magneto viscous effect. Results can be useful to develop a novel kind of bidispersed magnetorheological fluids to increase its commercial applicability.

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Hewlin, Rodward L., and Joseph M. Tindall. "Computational Assessment of Magnetic Nanoparticle Targeting Efficiency in a Simplified Circle of Willis Arterial Model." International Journal of Molecular Sciences 24, no. 3 (January 29, 2023): 2545. http://dx.doi.org/10.3390/ijms24032545.

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This paper presents the methodology and computational results of simulated medical drug targeting (MDT) via induced magnetism intended for administering intravenous patient-specific doses of therapeutic agents in a Circle of Willis (CoW) model. The multi-physics computational model used in this work is from our previous works. The computational model is used to analyze pulsatile blood flow, particle motion, and particle capture efficiency in a magnetized region using the magnetic properties of magnetite (Fe3O4) and equations describing the magnetic forces acting on particles produced by an external cylindrical electromagnetic coil. A Eulerian–Lagrangian technique is implemented to resolve the hemodynamic flow and the motion of particles under the influence of a range of magnetic field strengths (Br = 2T, 4T, 6T, and 8T). Particle diameter sizes of 10 nm to 4 µm in diameter were assessed. Two dimensionless numbers are also investigated a priori in this study to characterize relative effects of Brownian motion (BM), magnetic force-induced particle motion, and convective blood flow on particle motion. Similar to our previous works, the computational simulations demonstrate that the greatest particle capture efficiency results for particle diameters within the micron range, specifically in regions where flow separation and vortices are at a minimum. Additionally, it was observed that the capture efficiency of particles decreases substantially with smaller particle diameters, especially in the superparamagnetic regime. The highest capture efficiency observed for superparamagnetic particles was 99% with an 8T magnetic field strength and 95% with a 2T magnetic field strength when analyzing 100 nm particles. For 10 nm particles and an 8T magnetic field strength, the particle capture efficiency was 48%, and for a 2T magnetic field strength the particle capture efficiency was 33%. Furthermore, it was found that larger magnetic field strengths, large particle diameter sizes (1 µm and above), and slower blood flow velocity increase the particle capture efficiency. The key finding in this work is that favorable capture efficiencies for superparamagnetic particles were observed in the CoW model for weak fields (Br < 4T) which demonstrates MDT as a possible viable treatment candidate for cardiovascular disease.

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Øksendal, Audun N., T. Bach-Gansmo, T. Flem Jacobsen, H. Eide, and E. Andrew. "Oral Magnetic Particles." Acta Radiologica 34, no. 2 (January 1993): 187–93. http://dx.doi.org/10.3109/02841859309175348.

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Øksendal, A. N., T. Bach-Gansmo, T. Flem Jacobsen, H. Eide, and E. Andrew. "Oral Magnetic Particles." Acta Radiologica 34, no. 2 (March 1993): 187–93. http://dx.doi.org/10.1177/028418519303400217.

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Oral magnetic particles (OMP) have been evaluated in a clinical phase II trial program comprising 216 patients in 7 European centers. Adult patients referred for MR imaging for various abdominal pathologies were examined. The patients received OMP at a concentration of 0.1 g/l (ultralow field) or 0.5 g/l (mid/high field) and OMP was diluted in water or in a more viscous liquid formulation. Depending on the area of interest, OMP was ingested in a volume of 300 to 800 ml. OMP was well tolerated with no serious adverse events and the patient acceptability was good. OMP had a good contrast effect on all applied pulse sequences. The viscous formulation of OMP was homogeneously distributed through the entire gastrointestinal tract without inducing disturbing susceptibility artifacts. The postcontrast diagnostic information was improved in 70% of the cases. Based on the encouraging results in phase II, OMP has been advanced to phase III clinical trials.

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Marty, F., A. Vaterlaus, V. Weich, C. Stamm, U. Maier, and D. Pescia. "Ultrathin magnetic particles." Journal of Applied Physics 85, no. 8 (April 15, 1999): 6166–68. http://dx.doi.org/10.1063/1.370031.

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Yin, Shao Hui, Sheng Gong, Feng Jun Chen, and Ming Wang. "Research on Distribution of Magnetic Particles Based on Magnetic Field Control Grinding Wheel." Advanced Materials Research 797 (September 2013): 428–31. http://dx.doi.org/10.4028/www.scientific.net/amr.797.428.

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In order to solve the problem of the randomly arrangement of the diamond abrasives, a novel orderly arrangement grinding wheel was developed, which used magnetic field to control the magnetic particles to drive diamond abrasives orderly arrangement. Effects of magnetic flux density on magnetic particle distribution was studied. And effects of magnetic particle proportion on magnetic particle distribution was studied. Grinding experiments were carried out on the tungsten carbide YG8 and surface roughness after grinding was also analyzed.

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Li, Ze Lun, You Jun Huang, and Zhi Cheng Huang. "Particle Simulation of Slow-Wave System in Multi-Beam Traveling Wave Tube." Applied Mechanics and Materials 155-156 (February 2012): 381–85. http://dx.doi.org/10.4028/www.scientific.net/amm.155-156.381.

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A time-dependent particle code has been developed to simulate the motion and changing regularity of particles in multi-beam traveling wave tube. Magnetic focusing and interaction models of multi-beam traveling tube were established, and static magnetic field was calculated. The process of bunching particles by periodic permanent magnetic focusing system and beam-wave interaction was also simulated. The results show that particle simulation can really reflect the motion of particles in multi-beam traveling wave tube, which can provide some references for particle study of traveling wave tube.

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Ahrentorp, Fredrik, Andrea Astalan, Jakob Blomgren, Christian Jonasson, Erik Wetterskog, Peter Svedlindh, Aidin Lak, et al. "Effective particle magnetic moment of multi-core particles." Journal of Magnetism and Magnetic Materials 380 (April 2015): 221–26. http://dx.doi.org/10.1016/j.jmmm.2014.09.070.

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von Gladiss, Anselm, Matthias Graeser, Kerstin Lüdtke-Buzug, and Thorsten M. Buzug. "Contribution of brownian rotation and particle assembly polarisation to the particle response in magnetic particle spectrometry." Current Directions in Biomedical Engineering 1, no. 1 (September 1, 2015): 298–301. http://dx.doi.org/10.1515/cdbme-2015-0074.

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AbstractThe spectrometry of super-paramagnetic iron-oxide nanoparticles is a central tool for characterising particles that are used in Magnetic Particle Imaging. In Magnetic Particle Imaging, nanoparticles are excited by a magnetic field and the particle response is measured. Until now, the influence of the trajectory sequence on the dynamic particle relaxation has not been scoped. With a multi-dimensional Magnetic Particle Spectrometer, analysing the behaviour of different trajectories on the particles becomes possible. In this paper, the contribution of Brownian rotation and assembly polarisation on the particle signal is being analysed.

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Xuan, Xiangchun. "Recent Advances in Continuous-Flow Particle Manipulations Using Magnetic Fluids." Micromachines 10, no. 11 (October 31, 2019): 744. http://dx.doi.org/10.3390/mi10110744.

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Magnetic field-induced particle manipulation is simple and economic as compared to other techniques (e.g., electric, acoustic, and optical) for lab-on-a-chip applications. However, traditional magnetic controls require the particles to be manipulated being magnetizable, which renders it necessary to magnetically label particles that are almost exclusively diamagnetic in nature. In the past decade, magnetic fluids including paramagnetic solutions and ferrofluids have been increasingly used in microfluidic devices to implement label-free manipulations of various types of particles (both synthetic and biological). We review herein the recent advances in this field with focus upon the continuous-flow particle manipulations. Specifically, we review the reported studies on the negative magnetophoresis-induced deflection, focusing, enrichment, separation, and medium exchange of diamagnetic particles in the continuous flow of magnetic fluids through microchannels.

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31

Zhao, Xuefeng, Hao Qin, Yong Yang, Ke You, Xiaolong Yin, and Yin Yuan. "Study on magnetic preparation of dual disk based on silica gel magneto-elastic abrasive particles." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 39, no. 6 (December 2021): 1304–11. http://dx.doi.org/10.1051/jnwpu/20213961304.

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Magneto-elastic abrasive grains have magnetism, low elastic modulus and excellent abrasive performance, and have the characteristics of bonded abrasive grains and loose abrasive grains. The dual-disk magnetic preparation greatly improves the preparation quality and efficiency. Firstly, the magneto-elastic abrasive particles are introduced into the edge preparation of the dual-disk magnetic tool, and the preparation method of 4035 silica gel magneto-elastic abrasive particles is proposed. According to the microscopic characteristics of the magneto-elastic abrasive particles, the finite element software ABAQUS is used to establish the magneto-elastic abrasive particles. The meso-level representative volume element (RVE) model is built to analyze the stress and strain law of magneto-elastic abrasive particles under tension and compression. Secondly, an experimental platform for magnetic preparation of magneto-elastic abrasive particles with dual disks was built to analyze the force of magneto-elastic abrasive particles. Finally, Through the magnetic preparation experiment of the magneto-elastic abrasive dual-disk magnetic force, the influence of the disk rotation speed, abrasive particle size and relative magnetic permeability on the cutting edge wear is studied. And compared to the magnetic abrasive particles double-disk magnetic and drag finishing method, the magneto-elastic abrasive particle double-disk magnetic preparation method can obtain the maximum edge wear amount and the maximum surface roughness decreasing amplitude. The research results are of great significance to promote the progress of our country's magnetic high-efficiency processing and magneto-finishing processing technology.

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32

Martynov, S. I., and L. Y. Tkach. "Magnetic drive micro/nanomotor model." Journal of Physics: Conference Series 2103, no. 1 (November 1, 2021): 012082. http://dx.doi.org/10.1088/1742-6596/2103/1/012082.

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Abstract A model of a micro-/nanomotor with a hydrodynamic mechanism of motion due to the action of a rotating uniform external magnetic field is proposed. Micro-/nanomotor - is a chain of three charged particles, one of which has a magnetic moment. The total charge of the system is zero. In the absence of an external field, the particles are in equilibrium due to the action of the forces of attraction and repulsion, which corresponds to the minimum interaction energy. After applying a rotating magnetic field, a particle with a magnetic moment begins to rotate, forming a flow in the surrounding viscous fluid. The flow induces a hydrodynamic force that moves the chain in a specific direction. The forces of hydrodynamic interaction of particles with each other are taken into account, as well as internal forces holding the particles together. The dynamics of six model aggregates with one rotating particle is simulated numerically. The proposed mechanism for moving the chain can be used in the design of micro-/nanomotors and control them to deliver the payload.

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Browning, P. K., and G. E. Vekstein. "Particle Acceleration in Collisionless Magnetic Reconnection." Symposium - International Astronomical Union 203 (2001): 555–57. http://dx.doi.org/10.1017/s0074180900219980.

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We investigate the acceleration of charged particles in the framework of collisionless reconnection. A steady reconnection scenario is considered, with a two dimensional X-point magnetic field geometry having also a uniform field component transverse to the plane of the X-point field, and an inductive electric field generating an inflow of particles. Test particle trajectories are studied, and the energy spectra of the accelerated particles are determined.

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Chesnel, Karine, Dalton Griner, Dallin Smith, Yanping Cai, Matea Trevino, Brittni Newbold, Tianhan Wang, et al. "Unraveling Nanoscale Magnetic Ordering in Fe3O4 Nanoparticle Assemblies via X-rays." Magnetochemistry 4, no. 4 (September 20, 2018): 42. http://dx.doi.org/10.3390/magnetochemistry4040042.

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Understanding the correlations between magnetic nanoparticles is important for nanotechnologies, such as high-density magnetic recording and biomedical applications, where functionalized magnetic particles are used as contrast agents and for drug delivery. The ability to control the magnetic state of individual particles depends on the good knowledge of the magnetic correlations between particles when assembled. Inaccessible via standard magnetometry techniques, nanoscale magnetic ordering in self-assemblies of Fe3O4 nanoparticles is here unveiled via X-ray resonant magnetic scattering (XRMS). Measured throughout the magnetization process, the XRMS signal reveals size-dependent inter-particle magnetic correlations. Smaller (5 nm) particles show little magnetic correlations, even when packed close together, yielding to magnetic disorder in the absence of an external field, i.e., superparamagnetism. In contrast, larger (11 nm) particles tend to be more strongly correlated, yielding a mix of magnetic orders including ferromagnetic and anti-ferromagnetic orders. These magnetic correlations are present even when the particles are sparsely distributed.

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Kappe, Daniel, Laila Bondzio, Joris Swager, Andreas Becker, Björn Büker, Inga Ennen, Christian Schröder, and Andreas Hütten. "Reviewing Magnetic Particle Preparation: Exploring the Viability in Biosensing." Sensors 20, no. 16 (August 16, 2020): 4596. http://dx.doi.org/10.3390/s20164596.

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In this review article, we conceptually investigated the requirements of magnetic nanoparticles for their application in biosensing and related them to example systems of our thin-film portfolio. Analyzing intrinsic magnetic properties of different magnetic phases, the size range of the magnetic particles was determined, which is of potential interest for biosensor technology. Different e-beam lithography strategies are utilized to identify possible ways to realize small magnetic particles targeting this size range. Three different particle systems from 500 μm to 50 nm are produced for this purpose, aiming at tunable, vertically magnetized synthetic antiferromagnets, martensitic transformation in a single elliptical, disc-shaped Heusler Ni50Mn32.5Ga17.5 particle and nanocylinders of Co2MnSi-Heusler compound. Perspectively, new applications for these particle systems in combination with microfluidics are addressed. Using the concept of a magnetic on–off ratchet, the most suitable particle system of these three materials is validated with respect to magnetically-driven transport in a microfluidic channel. In addition, options are also discussed for improving the magnetic ratchet for larger particles.

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Kuryakov, VN, I. V. Sergeev, O. O. Efanova, and O. K. Zheludkova. "Investigation of the physicochemical properties of magnetic nanoparticles: size, magnetic properties, concentration." IOP Conference Series: Earth and Environmental Science 931, no. 1 (December 1, 2021): 012011. http://dx.doi.org/10.1088/1755-1315/931/1/012011.

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Abstract This work presents the results of studies of a series of samples of aqueous dispersions of magnetic nanoparticles. The particle sizes were measured for these samples by the dynamic scattering method. Using the method of ultramicroscopy, the number concentration of particles in the samples and the concentration of particles remaining in the volume of the samples after exposure to a magnetic field at various time intervals were measured.

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Behrends, André, Matthias Graeser, and Thorsten M. Buzug. "Introducing a frequency-tunable magnetic particle spectrometer." Current Directions in Biomedical Engineering 1, no. 1 (September 1, 2015): 249–53. http://dx.doi.org/10.1515/cdbme-2015-0062.

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AbstractImage quality in the new imaging modality magnetic particle imaging (MPI) heavily relies on the quality of the magnetic nanoparticles in use. Therefore, it is crucial to understand the behaviour of such particles. A common technique to analyze the behaviour of the particles is magnetic particle spectrometry (MPS). However, most spectrometers are limited to measurements at a single or multiple discrete excitation frequencies. This paper introduces a frequency-tunable spectrometer, able to perform measurements in the range of 100 Hz - 24kHz.

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38

Peng, Xiao Ling, Xiao Yang, Hai Biao Wei, Rui Ping Yue, and Hong Liang Ge. "Theoretical Modeling and Simulations of Magnetic Fluids in Gradient Magnetic Fields." Advanced Materials Research 146-147 (October 2010): 1510–13. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.1510.

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When a magnetic field is applied to magnetic fluids (MF), various structures of MF are formed: chain-like structures in low fields, columnar, lamellar and striped structures in high fields, ellipsoidal structures in pulsed fields, and layered structures in rotating fields. The inner structures and particle distributions of MF in gradient magnetic fields are quite interesting, but very few works have been done on this. In the present study, the effects of magnetic field gradient on the structures of MF are investigated using a two-dimensional Monte Carlo simulation. The results show that a gradient distribution of magnetic particles is formed under gradient magnetic fields. Moreover, with increasing the field gradient, more magnetic particles are pushed to the right region and particle distribution changes from grass-like clusters to needle-like ones.

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39

Luo, Laan, and Yongqing He. "Magnetically Induced Flow Focusing of Non-Magnetic Microparticles in Ferrofluids under Inclined Magnetic Fields." Micromachines 10, no. 1 (January 15, 2019): 56. http://dx.doi.org/10.3390/mi10010056.

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The ability to focus biological particles into a designated position of a microchannel is vital for various biological applications. This paper reports particle focusing under vertical and inclined magnetic fields. We analyzed the effect of the angle of rotation (θ) of the permanent magnets and the critical Reynolds number (Rec) on the particle focusing in depth. We found that a rotation angle of 10° is preferred; a particle loop has formed when Re < Rec and Rec of the inclined magnetic field is larger than that of the vertical magnetic field. We also conducted experiments with polystyrene particles (10.4 μm in diameter) to prove the calculations. Experimental results show that the focusing effectiveness improved with increasing applied magnetic field strength or decreasing inlet flow rate.

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40

Campuzano, Susana, Maria Gamella, Verónica Serafín, María Pedrero, Paloma Yáñez-Sedeño, and José Manuel Pingarrón. "Magnetic Janus Particles for Static and Dynamic (Bio)Sensing." Magnetochemistry 5, no. 3 (August 22, 2019): 47. http://dx.doi.org/10.3390/magnetochemistry5030047.

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Magnetic Janus particles bring together the ability of Janus particles to perform two different functions at the same time in a single particle with magnetic properties enabling their remote manipulation, which allows headed movement and orientation. This article reviews the preparation procedures and applications in the (bio)sensing field of static and self-propelled magnetic Janus particles. The main progress in the fabrication procedures and the applicability of these particles are critically discussed, also giving some clues on challenges to be dealt with and future prospects. The promising characteristics of magnetic Janus particles in the (bio)sensing field, providing increased kinetics and sensitivity and decreased times of analysis derived from the use of external magnetic fields in their manipulation, allows foreseeing their great and exciting potential in the medical and environmental remediation fields.

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Sobecki, Christopher, Jie Zhang, and Cheng Wang. "Dynamics of a Pair of Paramagnetic Janus Particles under a Uniform Magnetic Field and Simple Shear Flow." Magnetochemistry 7, no. 1 (January 19, 2021): 16. http://dx.doi.org/10.3390/magnetochemistry7010016.

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We numerically investigate the dynamics of a pair of circular Janus microparticles immersed in a Newtonian fluid under a simple shear flow and a uniform magnetic field by direct numerical simulation. Using the COMSOL software, we applied the finite element method, based on an arbitrary Lagrangian-Eulerian approach, and analyzed the dynamics of two anisotropic particles (i.e., one-half is paramagnetic, and the other is non-magnetic) due to the center-to-center distance, magnetic field strength, initial particle orientation, and configuration. This article considers two configurations: the LR-configuration (magnetic material is on the left side of the first particle and on the right side of the second particle) and the RL-configuration (magnetic material is on the right side of the first particle and on the left side of the second particle). For both configurations, a critical orientation determines if the particles either attract (below the critical) or repel (above the critical) under a uniform magnetic field. How well the particles form a chain depends on the comparison between the viscous and magnetic forces. For long particle distances, the viscous force separates the particles, and the magnetic force causes them to repel as the particle orientation increases above the configuration’s critical value. As the initial distance decreases, a chain formation is possible at a steady orientation, but is more feasible for the RL-configuration than the LR-configuration under the same circumstances.

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Zhang, Xing Ming, Hong Peng Zhang, Zhao Bo, Hai Quan Chen, and Yu Qing Sun. "Study on Magnetization and Detection the Metal Particle in Harmonic Magnetic Field." Key Engineering Materials 645-646 (May 2015): 790–95. http://dx.doi.org/10.4028/www.scientific.net/kem.645-646.790.

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Inductance detection methods of metal particle in hydraulic oil are generally based on the inductance change detection. With this method, when particles pass through the microchannel, ferromagnetic and non-ferromagnetic metal particle can be distinguished by monitoring inductance. In this study, it was found that not only inductance pulse but also resistance pulse was produced when detecting particle by inductance detection method. The theory of inductance or resistance change caused by particle is presented from the perspective of electromagnetism in this paper. To verify this phenomenon, the oil sample mixed with different metal particles was forced through the detection coil of microfluidic by constant flow rate. Then several sizes of iron and copper particles were measured. Experimental results showed that the resistance pulses caused by iron particles and copper particles were positive. And for copper particle, SNR (Signal Noise Ratio) of copper particles detected in improved effectively by detecting the resistance pulse.

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43

He, Yongqing, Laan Luo, and Shuang Huang. "Magnetic manipulation on the unlabeled nonmagnetic particles." International Journal of Modern Physics B 33, no. 07 (March 20, 2019): 1950047. http://dx.doi.org/10.1142/s0217979219500474.

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This paper reports two basic microfluidic strategies for the magnetic manipulation of unlabeled nonmagnetic particles/cells. One is the deflection induced by a single magnet, and the other is the confusing effect produced by two magnets of opposite polarity. They can be combined into more completed particle manipulations like continuous flow separation, counting and detection, which are essential steps in biomedical applications. We experimentally studied the dynamics of 10.4 and 20 [Formula: see text]m nonmagnetic polystyrene particles within a flow rate range of 30, 50, 70 and 90 [Formula: see text]L/min in a straight channel. We defined the cross-section length that the particles occupy as the “particle bandwidth” to characterize the extent of deflection and focusing. To predict the trajectories of the particles, we established a simple theoretical model by considering the magnetic force and viscous drag force. Compared with the experimental results, the maximum deviation of the simulation is 9.28%. The influences of magnetic nanoparticle concentration, magnetic field parameters, size of microparticles and flow rate are systematically investigated. We also demonstrated that the effective deflection and focusing could be realized at low Fe3O4 nanoparticle concentrations, which means that this method can reduce the damage on cells in the practical applications.

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Amiruddin, Erwin, and Adhy Prayitno. "The synthesis of magnetic nanoparticles from naturaliron sand of Kata beach Pariaman West Sumatera using ball milling method as environmental material." MATEC Web of Conferences 276 (2019): 06014. http://dx.doi.org/10.1051/matecconf/201927606014.

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Synthesis, magnetic, and structural properties and adsorption study of magnetic particles of Fe3O4 have been carried out. Magnetic particles were synthesized from natural iron sand of Kata Beach Pariaman West Sumatera using ball milling method. The structural properties of the samples were determined using X-Ray Diffractometer (XRD) technique. Magnetic properties such as magnetization were measured based on hysteresis loop using vibrating sample magnetometer (VSM). Mass susceptibility of the sample was measured using Pasco magnetic probe. It was found that the mass susceptibility of magnetic particles increased significantly as ball milling time increased. Based on VSM results, the magnetic particle of Fe3O4 has magnetization value of 32.26 emu/g with small coercivity of 174 Oe. Moreover, the results showed that ball milling method has succeeded to obtain magnetic particles. The increase of ball milling time resulted in an increase of magnetic moment of the sample. In this research, the magnetic particle of Fe3O4 was added to a solution of methyline blue performed using shaker method. Atomic Adsorption Spectroscopy (AAS) method was used to study the methylene blue degradation.

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45

Ido, Yasushi, Kazuya Arakawa, Keisuke Asakura, and Hitoshi Nishida. "Simulation of Behavior of Micrometer-Size Particles in the Polishing Process of a Micro-Tube Filled with a Magnetic Fluid under Uniform Magnetic Field." Materials Science Forum 721 (June 2012): 205–10. http://dx.doi.org/10.4028/www.scientific.net/msf.721.205.

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Behavior of suspended magnetic and nonmagnetic micrometer-size particles in a micro-tube filled with a magnetic fluid is investigated by using the discrete particle method based on the simplified Stokesian dynamics in order to know the polishing process of inner wall of a tube. It is shown that the chain-like clusters of magnetic particles are surrounded by clusters of nonmagnetic particles in the presence of uniform magnetic field. The clusters are held in the field direction in case of rotation of the micro-tube and in case of rotation of magnetic field.

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Lua, A. C., and R. F. Boucher. "Magnetic Filtration of Fine Particles from Gas Streams." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 207, no. 2 (August 1993): 109–22. http://dx.doi.org/10.1243/pime_proc_1993_207_214_02.

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Dust particles from the basic oxygen furnace steelmaking process were removed from air streams using a laboratory high-gradient magnetic filter. Particle sizes and number concentrations were determined by an optical particle spectrometer and were found to be largely in the submicrometre range. Dust loadability increased greatly when a magnetic field was applied and showed no deterioration in filter performance, even though the matrix had captured 10 times its own volume of dust. Particle penetrations of 1 per cent and less were achieved for submicrometre particles down to an optically measurable 0.24 μm diameter. Varying only one parameter at a time has isolated the individual effects of filter length, magnetic field, matrix packing fraction, gas velocity and wire size and aspect ratio. The dimensionless groups in an idealized single-wire model for high-gradient magnetic filtration are not adequate for a real filter. Other dimensionless parameters, viz. average dimensionless wire separation and cumulative dimensionless wire blockage, arise and are found to be important.

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Gassen, River, Dennis Thompkins, Austin Routt, Philippe Jones, Meghan Smith, William Thompson, Paul Couture, et al. "Optical Imaging of Magnetic Particle Cluster Oscillation and Rotation in Glycerol." Journal of Imaging 7, no. 5 (April 29, 2021): 82. http://dx.doi.org/10.3390/jimaging7050082.

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Magnetic particles have been evaluated for their biomedical applications as a drug delivery system to treat asthma and other lung diseases. In this study, ferromagnetic barium hexaferrite (BaFe12O19) and iron oxide (Fe3O4) particles were suspended in water or glycerol, as glycerol can be 1000 times more viscous than water. The particle concentration was 2.50 mg/mL for BaFe12O19 particle clusters and 1.00 mg/mL for Fe3O4 particle clusters. The magnetic particle cluster cross-sectional area ranged from 15 to 1000 μμm2, and the particle cluster diameter ranged from 5 to 45 μμm. The magnetic particle clusters were exposed to oscillating or rotating magnetic fields and imaged with an optical microscope. The oscillation frequency of the applied magnetic fields, which was created by homemade wire spools inserted into an optical microscope, ranged from 10 to 180 Hz. The magnetic field magnitudes varied from 0.25 to 9 mT. The minimum magnetic field required for particle cluster rotation or oscillation in glycerol was experimentally measured at different frequencies. The results are in qualitative agreement with a simplified model for single-domain magnetic particles, with an average deviation from the model of 1.7 ± 1.3. The observed difference may be accounted for by the fact that our simplified model does not include effects on particle cluster motion caused by randomly oriented domains in multi-domain magnetic particle clusters, irregular particle cluster size, or magnetic anisotropy, among other effects.

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Xia, Q., and V. Zharkova. "Particle acceleration in coalescent and squashed magnetic islands." Astronomy & Astrophysics 620 (December 2018): A121. http://dx.doi.org/10.1051/0004-6361/201833599.

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Aims. Magnetic reconnection in large Harris-type reconnecting current sheets (RCSs) with a single X-nullpoint often leads to the occurrence of magnetic islands with multiple O- and X-nullpoints. Over time these magnetic islands become squashed, or coalescent with two islands merging, as has been observed indirectly during coronal mass ejection and by in-situ observations in the heliosphere and magnetotail. These points emphasise the importance of understanding the basic energising processes of ambient particles dragged into current sheets with magnetic islands of different configuration. Methods. Trajectories of protons and electrons accelerated by a reconnection electric field are investigated using a test particle approach in RCSs with different 3D magnetic field topologies defined analytically for multiple X- and O-nullpoints. Trajectories, densities, and energy distributions are explored for 106 thermal particles dragged into the current sheets from different sides and distances. Results. This study confirms that protons and electrons accelerated in magnetic islands in the presence of a strong guiding field are ejected from a current sheet into the opposite semiplanes with respect to the midplane. Particles are found to escape O-nullpoints only through the neighbouring X-nullpoints along (not across) the midplane following the separation law for electrons and protons in a given magnetic topology. Particles gain energy either inside O-nullpoints or in the vicinity of X-nullpoints that often leads to electron clouds formed about the X-nullpoint between the O-nullpoints. Electrons are shown to be able to gain sub-relativistic energies in a single magnetic island. Energy spectra of accelerated particles are close to power laws with spectral indices varying from 1.1 to 2.4. The more squashed the islands the larger the difference between the energy gains by transit and bounced particles, which leads to their energy spectra having double maxima that gives rise to fast-growing turbulence. Conclusions. Particles are shown to gain the most energy in multiple X-nullpoints between O-nullpoints (or magnetic islands). This leads to the formation of electron clouds between magnetic islands. Particle energy gains are much larger in squashed islands than in coalescent ones. In summary, particle acceleration by a reconnection electric field in magnetic islands is much more effective than in an RCS with a single X-nullpoint.

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OZCAN, SINAN, CAHIT A. EVRENSEL, MARK A. PINSKY, and ALAN FUCHS. "DYNAMIC SIMULATION OF PRESSURE DRIVEN FLOW OF FLUIDS WITH SUSPENDED FERROUS PARTICLES IN A MICRO CHANNEL UNDER MAGNETIC FIELD." International Journal of Modern Physics B 21, no. 28n29 (November 10, 2007): 4890–97. http://dx.doi.org/10.1142/s0217979207045803.

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This computational study focuses on the dynamics of individual ferrous particles and the flow of the incompressible Newtonian fluid under the effect of an externally applied magnetic field and pressure gradient in a two-dimensional micro channel with smooth walls. The particle dynamics is simulated as a discrete phase using MATLAB code and the fluid flow is solved as a continuous phase using Computational Fluid Dynamics Software FLUENT. Interaction between the particle and fluid phases are included as hydrodynamic forces predicated by the fluid phase simulation and updated particle locations determined by the particle phase solution under non-uniform magnetic field. Non-uniform magnetic field forces the particles to move to poles of the magnet, and results in their accumulation. This causes drastic change on the continuous phase flow and pressure distribution, which in turn influences the particle motion. Predicted dynamics of the suspended ferrous particles under magnetic field and flow of the carrier fluid with pressure gradient is in reasonably well agreement with previous work. The results show that non-uniform magnetic field generated by externally placed magnets can be used to control the locations of the particles and flow of the fluid in a micro channel.

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Lee, Changje, and Yong-Seok Choi. "Experimental Investigation of Magnetic Particle Movement in Two-Phase Vertical Flow under an External Magnetic Field Using 2D LIF-PIV." Applied Sciences 10, no. 11 (June 8, 2020): 3976. http://dx.doi.org/10.3390/app10113976.

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In this study, we experimentally investigated magnetic particle movement in two-phase flow under an external magnetic field. According to Faraday’s law, the alignment of a magnet is important for power generation. For high generation, it is important to understand how magnetic particles move in two-phase flow. The rotationality could be determined by observing a single particle; however, this is impossible due to the flow conditions. In this study, we estimated nonrotationality based on the vorticity. To eliminate scattered light and improve the signal-to-noise ratio, the laser-induced fluorescence particle image velocimetry technique was used. The solenoid nozzle has a hydraulic diameter of 3 mm. Its surface is covered with a coil with a diameter of 0.3 mm. The average diameter of a magnetic particle is 1.2 μm. The excitation and emission wavelengths are 532 and 612 nm, respectively. A thin laser sheet setup was configured. The laser sheet was illuminated on both sides to prevent shadows. The images were captured at 200 μm away from the wall and center of the nozzle. To estimate the decrease in vorticity, the theoretical and single-phase non-magnetic and magnetic particles are compared. The vorticity of magnetic particles is reduced by the external magnetic field.

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Journal articles on the topic 'Magnetic particles'

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