Magnetic Patterns Research Articles

Magnetic fabric and sedimentological constraints on the paleocurrent changes within the early devonian strata from the northwestern Tarim, China

The magnetic fabric technique is widely used to measure the direction of paleocurrent and paleostress due to its speediness, precision, and cheapness. However, correlating unique magnetic fabric patterns in weakly deformed rocks with hydrodynamic or tectonic regimes remains challenging. The Early Devonian sedimentary rocks in the Keziertage Formation have well-preserved sedimentary structures and were deformed by the Cenozoic non-plunging fold. This sequence offers a prime opportunity to explore the relationship between magnetic fabric evolution, paleocurrents, and weakly deformation. Furthermore, the paleocurrent characteristics of the Keziertage Formation reflect the provenance changes during the opening of the South Tianshan Ocean. Here, we report 120 sedimentary structure-based paleocurrents and 382 magnetic fabric data from the Keziertage Formation in the Kalpin area, Xinjiang. We find that: (1) During the weakly deformation stage, the minimum axis of susceptibility's imbrication direction serves as a reliable indicator for detecting paleocurrents at the coarse sandstone layer with well-developed cross-bedding; (2) While the maximum axis of susceptibility is more consistent with the tectonic stress rather than paleocurrents. Consequently, the complexity of magnetic fabric needs to be clearly verified when it is applied in the weakly deformed strata. In the northwest margin of Tarim, both the minimum susceptibility axes of magnetic fabrics and sedimentary structures indicate a shift in the paleocurrent direction, transitioning from southwest to northeast in the mid-to-upper Keziertage Formation. This indicates significant channel changes, potentially linked to a regional change in provenance due to the Early Devonian opening of the South Tianshan Ocean.

A Two-Dimensional Transient Computational Multi-Physics Model for Analyzing Magnetic and Non-Magnetic Particle (Red Blood Cells and E. Coli Bacteria) Dynamics in a Traveling Wave Ferro-Magnetic Microfluidic Device for Potential Cell Separation and Sorting

Abstract This paper presents the theory and development, validation, and results of a transient computational multiphysics model for analyzing the magnetic field, particle dynamics, and capture efficiency of magnetic and nonmagnetic (e.g., Red Blood Cells and E. Coli bacteria) microparticles in a traveling wave ferromagnetic microfluidic device. This computational model demonstrates proof-of-concept of a method for greatly enhancing magnetic bioseparation in ferromicrofluidic systems using an array of copper conductive elements arranged in quadrature to create a periodic potential energy landscape. In contrast to previous works, our approach theoretically uses a microfluidic device with an electronic chip platform consisting of integrated copper electrodes that carry currents to generate programable magnetic field gradients locally. Alternating currents are applied to the electrodes in quadrature (using a 90 deg phase change from the neighboring electrode) to create a periodic magnetic field pattern that travels along the length of the microchannel. Our previous work evaluated magnetic and nonmagnetic particles in a static magnetic field within the same channel geometry. This work is a phase 2 study that expands on the previous work and analyzes the dynamics of magnetic and nonmagnetic entities characterized by material magnetic susceptibility in a transient magnetic field. This is an improvement over our previous work. The model, which is described in more detail in the methods section, combines a Eulerian-Lagrangian and two-way particle-fluid coupling CFD analysis with closed-form magnetic field analysis that is used to predict magnetic separation considering dominant magnetic and hydrodynamic forces similar to our previous works in magnetic drug targeting. The model was also validated with an experimental low frequency stationary flow study on separating nonmagnetic latex fluorescent particles in a water based ferrofluid. The results from the experimental study and the developed model demonstrate that the proposed device may potentially be used as an effective platform for microparticle and cellular manipulation and sorting. The developed multiphysics model could potentially be used as a design optimization tool for traveling wave ferromicrofluidic devices.

Electric field-controlled deterministic magnetization reversal in nanomagnet Fe3Si/PMN-PT multiferroic heterostructures

Pure electric field-controlled 180° magnetization switching plays a vital role in low-power magnetoelectric memory devices. Using micromagnetic simulation, we engineered a square-shaped epitaxial Fe3Si nanomagnet on a PMN-PT piezoelectric substrate to make the magnetic easy axis slightly deviate 18° from the piezostrain axis, aiming to break the symmetry of the magnetization distribution and achieve deterministic magnetization reversal paths. Under the coaction of a magnetic field and an electric field, the simulated magnetic hysteresis loops and magnetic domain patterns reveal a fourfold to twofold magnetic anisotropy transition and magnetization reversal paths. Stimulated by pure electric field-induced piezoelectric strain, deterministic 180° magnetization reversals are accomplished by the two successive clockwise 90° switching process. The results help to comprehend electrically regulated deterministic magnetization reversal and pave an avenue for designing multistate spintronics devices.

Magneto-optical diffraction of visible light as a probe of nanoscale displacement of domain walls at femtosecond timescales.

Using diffraction of femtosecond laser pulses of visible light by a magnetic domain pattern in an iron garnet, we demonstrate a proof of concept of time-resolved measurements of domain pattern movements with nanometer spatial and femtosecond temporal resolution. In this method, a femtosecond laser (pump) pulse initiates magnetization dynamics in a sample that is initially in a labyrinth domain state, while an equally short linearly polarized laser pulse (probe) is diffracted by the domain pattern. The components of the diffracted light that are polarized orthogonally to the incident light generate several concentric diffraction rings. Nanometer small changes in the relative sizes of domains with opposite magnetization result in observable changes in the intensities of the rings. We demonstrate that the signal-to-noise ratio is high enough to detect a 6nm domain wall displacement with 100fs temporal resolution using visible light. We also discuss possible artifacts, such as pump-induced changes of optical properties, that can affect the measurements.

Probing the photo induced micro actuation properties of optimized Cu doped Co-34at%-Ni-35at%-Al-31at% ferromagnetic shape memory alloys

The strange Photo induced micro actuation (PIMA) properties associated with Cu doped Co-Ni-Al Ferromagnetic Shape Memory Alloys (FSMA) has showed enhancement of mechanical properties in our early studies. This enhancement and optimized PIMA properties have opened a scope of various laser-controlled real engineering applications. In this study, we have explored the microstructural scaling and determined the evolved force due to the laser action in optimized Cu doped Co-Ni-Al alloy system with a detailed insight. This unique PIMA property is rare in literature and actual reason are still not explored. EBSD, TEM, AFM/MFM based techniques were further adopted to understand the role of microstructure in more detail. The evolved magnetic domain patterns for actuating and non-actuating alloys have been analyzed in details. Atomic Force Microscopy was adopted to estimate the constitutive mechanical properties of the thin alloy samples by mechanical spectrometry. This estimation was directly used to predict a general trend in force distribution pattern of the Cu-Co-Ni-Al alloys strips through FEM analysis. The crux of FEM based model and its simulated results can be applied for real time PIMA oriented engineering application and device manufacturing. The detail microstructural exploration and its effect in the PIMA response along with generalized deflection-force model have been presented in the current study.

Polymer-nanoparticle thin scaffolds with any-shape magnetic field gradients

This study investigates the self-assembly of magnetic nanoparticles into a flat nanocomposite surface with concealed magnetic patterns. The application of a multilayer stamping medium and the presence of a magnetic field gradient would enable the attraction and organization of superparamagnetic iron oxide nanoparticles (SPIONs) onto predefined areas, corresponding to a pre-fabricated magnetic layer. The experimental approach involved preparing patterned surfaces by applying a multilayer of poly(ethyleneimine) (PEI) and poly(styrene sulfonate) (PSS) as a stamping medium. The SPIONs selectively adhered to the surface, mirroring the underlying magnetic layer shape. Subsequently, these SPION were subjected to an 80 °C treatment in the presence of an external magnetic field to enhance their magnetic properties, and then covered with a polystyrene layer. Using atomic force microscopy, magnetic force microscopy and dark field mode optical microscopy we demonstrated that obtained patterned magnetic field gradients are strong enough to attract and organize magnetic material on top of them, even when being covered with polymeric layers. Moreover, our findings show that the oriented deposition of magnetic nanoparticles is primarily determined by the strength of magnetic interactions between the pattern and nanoparticles, independently of surface topography (with roughness of 0.21 ± 0.06 nm) or Brownian motions.

Online Short-Circuit Fault Diagnosis in Three-Core Power Distribution Cable Based on Magnetic Pattern

Online Short-Circuit Fault Diagnosis in Three-Core Power Distribution Cable Based on Magnetic Pattern

A unique case of a fulminant clonal CD8-positive T-cell lymphoproliferative disorder with CNS involvement

BackgroundThis is a unique case that describes the presentation, investigations, and disease trajectory of a fatal, clonal CD8-positive T-cell lymphoproliferative disorder in an otherwise healthy and immunocompetent patient with Epstein-Barr virus seronegative status. Central nervous system involving T-cell lymphoproliferative disorders are rare and typically encountered in the setting of immunocompromise. These disorders are often associated with aggressive cytomorphological features and characteristic magnetic resonance imaging patterns, which were not seen in this case.Case presentationHere we describe a case of a 65 year-old male presenting with neuropsychiatric symptoms, truncal ataxia, and falls who’s bone marrow, cerebrospinal fluid, and brain biopsy were consistent with a clonal CD8-positive T-cell lymphoproliferative disorder that did not meet existing World Health Organization criteria for classification as T-cell lymphoma. The patient was treated with intrathecal methotrexate resulting in transient improvement of his symptoms followed by disease progression and death related to aspiration.ConclusionsThis case highlights the importance of urgent and comprehensive work-up in patients with clinical features suggestive of lymphoma with central nervous system involvement, despite atypical imaging features and lack of cytomorphological features satisfying current World Health Organization classification criteria.

Antiferromagnet on Pyrochlore Lattice in Spherical Approximation

"We develop an 1/n expansion method for the systematic approximation of the solutions of classical spin systems (tri-dimensional vectors) which can describe general spin-spin interactions and phases with complex magnetization pattern. This method is applied to study the phase transitions observed in pyrochlore crystals (e.g. Gd2Ti2O7) and the results have qualitative agreement with the experimental ones."

Magnetic Fabric and Paleomagnetic Analyses of the Zaghar and Tafresh Areas, Central Urumieh-Dokhtar Magmatic Arc, Iran

Magnetic fabric, paleomagnetic, and petrophysical studies were conducted on rocks in the Tafresh area of the central Urumieh-Dokhtar magmatic arc in Iran. The samples included Late Triassic dark gray sandstone, a mafic dyke, diorites, and a felsic dyke in the Zaghar region. Hydrothermal alteration in the Spid intrusion was investigated to understand the effects of alteration on magnetic fabric patterns. The AMS measurements support the theory that the Nayband Formation was constructed under a crustal extension regime. Magnetic susceptibility anisotropy in a microdioritic dyke indicates compression from the NNE-SSW, likely due to tectonic activity. AMS results from diorites in Zaghar suggest intrusions were emplaced in extensional spaces between the Tafresh and Chaghar thrust faults. The Spid intrusion’s magnetite is the primary carrier of magnetic susceptibility, but hydrothermal alteration has partly converted it into hematite, resulting in lower susceptibility and higher porosity in altered diorites. This process leads to a bimodal distribution of magnetic lineation trends. The Spid and Zaghar massifs underwent a northward tilt of about 30 degrees around an east-west axis following the Early Miocene. Post-Eocene rotations in the area are typically within ±20 degrees. This study demonstrates how magnetic properties can provide new insights into the evolution of tectono-magmatic processes and structural controls within a magmatic arc.

Climatology of quiet time geomagnetic field variations at two locations in Antarctica

During geomagnetic quiet conditions, Indian Antarctic stations are considered to be located outside the auroral oval: Maitri (CGM coordinates: 63.3°S, 54.2°E) is equatorward and Bharati (CGM coordinates: 74.8°S, 98.4°E) is poleward of the auroral oval. Simultaneous observations of magnetic field variations at these two locations for 10-years (2013–2022) provide an opportunity to study quiet-time magnetic field patterns, if any. Geomagnetic quiet days with ΣKp ≤ 3 are selected, during which the lower values of solar wind and interplanetary parameters are also confirmed. Maitri station exhibits clear southern hemispheric solar quiet (Sq) type of magnetic field variation on geomagnetic quiet days in all seasons, indicating the influence of ionospheric dynamo due to thermospheric winds. Interestingly, Bharati station also displays regular and systematic magnetic field variations in all three components. The D-component at Bharati exhibits very strong variation at early morning hours (7–8 MLT), which is ∼2–4 times stronger than that of H-component, driving strong equatorward/northward currents during all seasons. Both stations show annual type of seasonal variation with peak amplitude during summer and least during winter. The schematic illustration of global and polar Sqs proposed here explains the results obtained through 10-years’ statistical study.

Elevated representational similarity of voluntary action and inhibition in Tourette syndrome.

Many people with Tourette syndrome are able to volitionally suppress tics, under certain circumstances. To understand better the neural mechanisms that underlie this ability, we used functional magnetic resonance neuroimaging to track regional brain activity during performance of an intentional inhibition task. On some trials, Tourette syndrome and comparison participants internally chose to make or withhold a motor action (a button press), while on other trials, they followed 'Go' and 'NoGo' instructions to make or withhold the same action. Using representational similarity analysis, a functional magnetic resonance neuroimaging multivariate pattern analysis technique, we assessed how Tourette syndrome and comparison participants differed in neural activity when choosing to make or to withhold an action, relative to externally cued responses on Go and NoGo trials. Analyses were pre-registered, and the data and code are publicly available. We considered similarity of action representations within regions implicated as critical to motor action release or inhibition and to symptom expression in Tourette syndrome, namely the pre-supplementary motor area, inferior frontal gyrus, insula, caudate nucleus and primary motor cortex. Strikingly, in the Tourette syndrome compared to the comparison group, neural activity within the pre-supplementary motor area displayed greater representational similarity across all action types. Within the pre-supplementary motor area, there was lower response-specific differentiation of activity relating to action and inhibition plans and to internally chosen and externally cued actions, implicating the region as a functional nexus in the symptomatology of Tourette syndrome. Correspondingly, patients with Tourette syndrome may experience volitional tic suppression as an effortful and tiring process because, at the top of the putative motor decision hierarchy, activity within the population of neurons facilitating action is overly similar to activity within the population of neurons promoting inhibition. However, not all pre-supplementary motor area group differences survived correction for multiple comparisons. Group differences in representational similarity were also present in the primary motor cortex. Here, representations of internally chosen and externally cued inhibition were more differentiated in the Tourette syndrome group than in the comparison group, potentially a consequence of a weaker voluntary capacity earlier in the motor hierarchy to suppress actions proactively. Tic severity and premonitory sensations correlated with primary motor cortex and caudate nucleus representational similarity, but these effects did not survive correction for multiple comparisons. In summary, more rigid pre-supplementary motor area neural coding across action categories may constitute a central feature of Tourette syndrome, which can account for patients' experience of 'unvoluntary' tics and effortful tic suppression.

Total variation regularized phase retrieval algorithm for diffraction imaging analysis of magnetic domain patterns

Total variation regularized phase retrieval algorithm for diffraction imaging analysis of magnetic domain patterns

Synthesis, Structural, Spectral Studies and Activity Studies of 6-Methyl-4-(3-Nitro-Phenyl)-2-Oxo-1,2,3,4 Tetrahydropyrimidine-5-Carboxylic Acid Ethyl Ester Catalyzed Using BF3-OEt2

Amide compounds exhibit tautomerism which is an important property in organic synthesis. Evidence for the occurrence of tautomeric forms for amido-imidols is interpreted via mass spectrometry techniques. The tautomeric equilibrium of pyrimidone moiety was rationalized and the existence of amido-imidol tautomerism in 6-methyl-4-(3-nitro-phenyl)-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid ethyl ester (6M3NP) was verified. The proton nuclear magnetic resonance splitting pattern shows the intramolecular hydrogen bonding between the keto-enol forms which evidences through a fluctuation in the integration value of C4 proton. Synthesis proceeds through novel BF3-OEt2 catalysed one-pot, simple, efficient, minimal catalyst usage, compatible, outstanding yield, and rapid protocol for the Tetrahydropyrimidinones via Biginelli reaction is described. The titled compound 6M3NP was characterized by infrared and nuclear magnetic resonance. The compound was screened for antimicrobial activity against 3 microbes which showed a high zone of inhibition when compared to standard streptomycin. The antioxidant activity using 2,2-diphenyl-1-picryl-hydrazyl-hydrate assay gave a promising IC50 value of 14.11 µM. The more the radical scavenging activity the greater the chance of functioning as an anticancer agent. 6M3NP was tested against breast cancer cells after scrutiny with 60 cell lines. Clonogenicity and soft agar colony formation were significantly reduced in MCF7, MDA-MB-231, and T47D breast cancer cells after treatment with 6M3NP. The in-silico dock score obtained for the title compound was 62.845 which is 40% more than the standard drug Nifedipine. In-vitro cell line analysis results showed that the title compound possesses maximum activity than commercial drug Nifedipine against cardiovascular disease as a calcium channel blocker.

Tunable Magnetic Domain Patterns in Thickness-Gradient Nickel Films on Flexible PDMS Substrates.

Flexible magnetoelectronic devices (based on magnetic films) have great application prospects in the fields of information storages, bionic robotics, and electronic skins. The intrinsic stress and external loading are very important to modulate the structures and properties of flexible magnetic films due to the magnetoelastic coupling effect. Here, we report on tunable magnetic domain patterns in thickness-gradient nickel (Ni) films deposited on flexible polydimethylsiloxane substrates. It is found that stripe magnetic domains spontaneously form in the Ni films and their sizes increase with the film thickness. The internal stress evolves from tensile to compressive states with decreasing film thickness, leading to the formation of cracks in thicker regions and wrinkles in thinner regions. Meanwhile, the orientations of stripe magnetic domains change from the gradient direction to the orthogonal direction. The structural features, evolution behaviors, and physical mechanisms of the cracks, wrinkles, and magnetic domains are analyzed based on the stress theory and magnetoelastic coupling. Periodic gradient Ni films with large-scale regulations of stripe magnetic domains are also realized by masking of copper grids. This study helps to better understand the magnetoelastic coupling effect in gradient flexible magnetic films and provides a technique to modulate anisotropic magnetic properties by designing specific film systems.

Toward using the Villari effect for non-destructive evaluation of steel structures

This work follows on from studies carried out by Jiles and Atherton on magnetic hysteresis and on the magnetomechanical effect. The Jiles–Atherton equation, which models the rate of change of magnetization with respect to stress, was solved numerically in the forward and reverse directions for stress up to 90 MPa, suggesting that stressing carbon steel will cause a lasting change in the magnetization of the sample. This was confirmed experimentally by measuring the B-field in proximity to samples of C45 steel while undergoing tensile stress, with the pattern of magnetization suggesting that the magnetic domains reorient themselves in the geomagnetic field when stressing loosens their pinning. A further experiment on two samples confirms this, with the B-field around the samples showing strong changes according to their orientation in the geomagnetic field at the time of the stressing. This work has relevance to the non-destructive testing of steel structures such as pipelines, and the relevance of the experiments to this work is considered, as well as future prospects.

Activity time series of old stars from late F to early K

Context. Stellar variability impacts radial velocities (hereafter RVs) at various timescales and therefore the detectability of exoplanets and the mass determination based on this technique. Detecting and characterising Earth-like planets in the habitable zone of solar-type stars represents an important challenge in the coming years, however. It is therefore necessary to implement systematic studies of this issue, for example to delineate the current limitations of RV techniques. Aims. A first aim of this paper is to investigate whether the targeted 10% mass uncertainty from RV follow-up of transits detected by PLATO can be reached. A second aim of this paper is to analyse and quantify Earth-like planet detectability for various spectral types. Methods. For this purpose, we implemented blind tests based on a large data set (more than 20 000) of realistic synthetic time series reproducing different phenomena leading to stellar variability such as magnetic activity patterns similar to the solar configuration as well as flows (oscillations, granulation, and supergranulation), covering F6-K4 stars and a wide range of activity levels. Results. We find that the 10% mass uncertainty for a 1 MEarth in the habitable zone of a G2 star cannot be reached, even with an improved version of the usual correction of stellar activity (here based on a non-linear relation with log R′HK and cycle phase instead of a linear correlation) and even for long-duration (10 yr) well-sampled observations. This level can be reached, however, for masses above 3 MEarth or for K4 stars alone. We quantify the maximum dispersion of the RV residuals needed to reach this 10% level, assuming the activity correction method and models do not affect the planetary signal. Several other methods, also based on a correction using log R′HK in various ways (including several denoising techniques and Gaussian processes) or photometry, were tested and do not allow a significantly improvement of this limited performance. Similarly, such low-mass planets in the habitable zone cannot be detected with a similar correction: blind tests lead to very low detection rates for 1 MEarth and to a very high level of false positives. We also studied the residuals after correction of the stellar signal, and found significant power in the periodogram at short and long timescales, corresponding to masses higher than 1 MEarth in this period range. Conclusions. We conclude that very significant and new improvements with respect to methods based on activity indicators to correct for stellar activity must be devised at all timescales to reach the objective of 10% uncertainty on the mass or to detect such planets in RV. Methods based on the correlation with activity indicators are unlikely to be sufficient.

Eddy Current Testing Based Non-Destructive Inspection for Metal 3D Additive Manufacturing Objects With HTS-SQUID

In this work, we applied eddy-current-testing-based HTS-SQUID non-destructive inspection (ECT-based HTS-SQUID NDI) system for inspection of metal 3D additive manufacturing (AM) objects, which were made of AlSi10Mg powder with powder bed fusion (PBF) method. The inspection system combines an ECT probe with an HTS-SQUID gradiometer as high sensitive readout magnetic sensor in low frequency range to overcome disadvantage of conventional ECT. We prepared 5 samples with different densities by changing parameters in the PBF process. Densities of the samples #1-#5 were estimated to be 2.65, 2.64, 2.62, 2.58, and 2.51 g/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , respectively. The samples were measured by the inspection system with an excitation current of 20 mA at 1.6 kHz, and lift-off of about 1 mm. In inspection results, anomalous magnetic patterns appeared on the sample #3, #4 and #5. The inspection results were verified with X-ray CT scanning. Comparison between the ECT inspection and the X-ray CT results reveals that the positions of the anomalous magnetic patterns show strong correlation with the positions of high porosity existing in the samples.

Analytical model for double-sided linear permanent magnet inner armature synchronous machine with slot-less stator at on-load in different patterns of magnetization

Analytical model for double-sided linear permanent magnet inner armature synchronous machine with slot-less stator at on-load in different patterns of magnetization

Exact and Computationally Robust Solutions for Cylindrical Magnets Systems with Programmable Magnetization.

Magnetic systems based on permanent magnets are receiving growing attention, in particular for micro/millirobotics and biomedical applications. Their design landscape is expanded by the possibility to program magnetization, yet enabling analytical results, crucial for containing computational costs, are lacking. The dipole approximation is systematically used (and often strained), because exact and computationally robust solutions are to be unveiled even for common geometries such as cylindrical magnets, which are ubiquitously used in fundamental research and applications. In this study, exact solutions are disclosed for magnetic field and gradient of a cylindrical magnet with generic uniform magnetization, which can be robustly computed everywhere within and outside the magnet, and directly extend to magnets systems of arbitrary complexity. Based on them, exact and computationally robust solutions are unveiled for force and torque between coaxial magnets. The obtained analytical solutions overstep the dipole approximation, thus filling a long-standing gap, and offer strong computational gains versus numerical simulations (up to 106 , for the considered test-cases). Moreover, they bridge to a variety of applications, as illustrated through a compact magnets array that could be used to advance state-of-the-art biomedical tools, by creating, based on programmable magnetization patterns, circumferential and helical force traps for magnetoresponsive diagnostic/therapeuticagents.