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Molecules (Basel, Switzerland) Feb 2021The effective spin Hamiltonian method has drawn considerable attention for its power to explain and predict magnetic properties in various intriguing materials. In this... (Review)
Review
The effective spin Hamiltonian method has drawn considerable attention for its power to explain and predict magnetic properties in various intriguing materials. In this review, we summarize different types of interactions between spins (hereafter, spin interactions, for short) that may be used in effective spin Hamiltonians as well as the various methods of computing the interaction parameters. A detailed discussion about the merits and possible pitfalls of each technique of computing interaction parameters is provided.
Topics: Magnetic Phenomena; Magnets; Models, Theoretical
PubMed: 33557181
DOI: 10.3390/molecules26040803 -
ELife Sep 2017Eye movements provide insights about a wide range of brain functions, from sensorimotor integration to cognition; hence, the measurement of eye movements is an important...
Eye movements provide insights about a wide range of brain functions, from sensorimotor integration to cognition; hence, the measurement of eye movements is an important tool in neuroscience research. We describe a method, based on magnetic sensing, for measuring eye movements in head-fixed and freely moving mice. A small magnet was surgically implanted on the eye, and changes in the magnet angle as the eye rotated were detected by a magnetic field sensor. Systematic testing demonstrated high resolution measurements of eye position of <0.1°. Magnetic eye tracking offers several advantages over the well-established eye coil and video-oculography methods. Most notably, it provides the first method for reliable, high-resolution measurement of eye movements in freely moving mice, revealing increased eye movements and altered binocular coordination compared to head-fixed mice. Overall, magnetic eye tracking provides a lightweight, inexpensive, easily implemented, and high-resolution method suitable for a wide range of applications.
Topics: Animals; Eye Movements; Magnetics; Mice; Mice, Inbred C57BL; Reflex, Vestibulo-Ocular; Video Recording
PubMed: 28872455
DOI: 10.7554/eLife.29222 -
Scientific Reports Jul 2022Magnetic compression technique (MCT) is a popular new anastomosis method. In this paper, we aimed to explore the feasibility of use of MCT for performing cystotomy in...
Magnetic compression technique (MCT) is a popular new anastomosis method. In this paper, we aimed to explore the feasibility of use of MCT for performing cystotomy in rabbits. The parent magnets and daughter magnets for rabbit cystostomy were designed and manufactured according to the anatomical characteristics of rabbit lower urinary tract. Twelve female New Zealand rabbits were used as animal models. After anesthesia, a daughter magnet was inserted into the bladder through the urethra, and the parent magnet was placed on the body surface projection of the bladder over the abdominal wall. The two magnets automatically attract each other. Postoperatively, the state of magnets was monitored daily, and the time when the magnets fell off was recorded. Cystostomy with MCT was successfully performed in all twelve rabbits. The mean operation time was 4.46 ± 0.75 min. The magnets fell off from the abdominal wall after a mean duration of 10.08 ± 1.62 days, resulting in the formation of bladder fistula. Macroscopic and microscopic examination showed that the fistula was well formed and unobstructed. The junction between bladder and abdominal wall was tight and smooth. We provide preliminary experimental evidence of the safety and feasibility of cystostomy based on MCT.
Topics: Animals; Cystostomy; Female; Magnetic Phenomena; Magnetics; Magnets; Pressure; Rabbits
PubMed: 35842556
DOI: 10.1038/s41598-022-16595-4 -
World Journal of Gastroenterology Oct 2012Reports of magnet ingestion are increasing rapidly globally. However, multiple magnet ingestion, the subsequent potential complications and the importance of the early... (Review)
Review
Reports of magnet ingestion are increasing rapidly globally. However, multiple magnet ingestion, the subsequent potential complications and the importance of the early identification and proper management remain both under-recognized and underestimated. Published literature on such cases could possibly represent only the tip of an iceberg with press reports, web blogs and government documents highlighting further occurrence of many more such incidents. The increasing number of complications worldwide being reported secondary to magnet ingestion point not only to an acute lack of awareness about this condition among the medical profession but also among parents and carers who will be in most cases the first to pick up on magnet ingestion. There still seems to be no consensus on the management of magnet ingestion with several algorithms being proposed for management. Prevention of this condition remains a much better option than cure. Proper education and improved awareness among parents and carers and frontline medical staff is key in addressing this rapidly emerging problem. The goal of managing such cases of suspected magnet ingestion should be aimed at reducing delays between ingestion time, diagnosis time and intervention time.
Topics: Child; Foreign Bodies; Humans; Intestinal Perforation; Intestines; Magnets
PubMed: 23082048
DOI: 10.3748/wjg.v18.i38.5324 -
Proceedings of the National Academy of... Nov 2022Magnetic materials are essential for energy generation and information devices, and they play an important role in advanced technologies and green energy economies....
Magnetic materials are essential for energy generation and information devices, and they play an important role in advanced technologies and green energy economies. Currently, the most widely used magnets contain rare earth (RE) elements. An outstanding challenge of notable scientific interest is the discovery and synthesis of novel magnetic materials without RE elements that meet the performance and cost goals for advanced electromagnetic devices. Here, we report our discovery and synthesis of an RE-free magnetic compound, FeCoB, through an efficient feedback framework by integrating machine learning (ML), an adaptive genetic algorithm, first-principles calculations, and experimental synthesis. Magnetic measurements show that FeCoB exhibits a high magnetic anisotropy ( = 1.2 MJ/m) and saturation magnetic polarization ( = 1.39 T), which is suitable for RE-free permanent-magnet applications. Our ML-guided approach presents a promising paradigm for efficient materials design and discovery and can also be applied to the search for other functional materials.
Topics: Feedback; Magnets; Magnetics; Metals, Rare Earth; Magnetic Phenomena; Machine Learning
PubMed: 36375053
DOI: 10.1073/pnas.2204485119 -
Cells Mar 2022The importance of magnetic micro- and nanoparticles for applications in biomedical technology is widely recognised. Many of these applications, including tissue... (Review)
Review
The importance of magnetic micro- and nanoparticles for applications in biomedical technology is widely recognised. Many of these applications, including tissue engineering, cell sorting, biosensors, drug delivery, and lab-on-chip devices, require remote manipulation of magnetic objects. High-gradient magnetic fields generated by micromagnets in the range of 10-10 T/m are sufficient for magnetic forces to overcome other forces caused by viscosity, gravity, and thermal fluctuations. In this paper, various magnetic systems capable of generating magnetic fields with required spatial gradients are analysed. Starting from simple systems of individual magnets and methods of field computation, more advanced magnetic microarrays obtained by lithography patterning of permanent magnets are introduced. More flexible field configurations can be formed with the use of soft magnetic materials magnetised by an external field, which allows control over both temporal and spatial field distributions. As an example, soft magnetic microwires are considered. A very attractive method of field generation is utilising tuneable domain configurations. In this review, we discuss the force requirements and constraints for different areas of application, emphasising the current challenges and how to overcome them.
Topics: Cell Separation; Magnetic Fields; Magnetics; Magnets; Nanoparticles
PubMed: 35326401
DOI: 10.3390/cells11060950 -
Journal of Chromatography. A Dec 2022Magnetic ionic liquids (MILs) are materials of special interest in analytical chemistry and, particularly, in analytical microextraction. These solvents possess several... (Review)
Review
Magnetic ionic liquids (MILs) are materials of special interest in analytical chemistry and, particularly, in analytical microextraction. These solvents possess several of the properties derived from their inherent nature of ionic liquids, combined with their magnetism, that permits their manipulation with an external magnetic field. This feature allows for performing typical steps of the microextraction procedure in a simpler manner with the aid of a strong magnet. Although there are several important reviews summarizing the most innovative advances in this field, there is a gap of information, as they do not provide useful details and tips related to the experimental set up of these procedures. This tutorial review fills this gap by providing a guide for the proper handling of MILs, their manipulation with magnets, and their proper hyphenation with the most used analytical techniques. Attention is paid to dispersive liquid-liquid microextraction, stir-bar dispersive liquid microextraction, aqueous biphasic systems, and single-drop microextraction, for being the analytical microextraction techniques mostly employed with MILs. This review also introduces a classification of the MILs employed in analytical microextraction in three classes (denoted as A, B, and C) as a function of the MIL nature (metal-containing anion, metal-containing cation, and radical-containing ion), and discuss about the prospect and future trends regarding new MIL families in microextraction together with new directions expected in these procedures.
Topics: Humans; Ionic Liquids; Liquid Phase Microextraction; Magnetics; Solvents; Magnetic Phenomena
PubMed: 36323106
DOI: 10.1016/j.chroma.2022.463577 -
Magma (New York, N.Y.) Apr 2023The Iseult MRI is an actively shielded whole-body magnet providing a homogeneous and stable magnetic field of 11.7 T. After nearly 20 years of research and development,... (Review)
Review
OBJECTIVES
The Iseult MRI is an actively shielded whole-body magnet providing a homogeneous and stable magnetic field of 11.7 T. After nearly 20 years of research and development, the magnet successfully reached its target field strength for the first time in 2019. This article reviews its commissioning status, the gradient-magnet interaction test results and first imaging experience.
MATERIALS AND METHODS
Vibration, acoustics, power deposition in the He bath, and field monitoring measurements were carried out. Magnet safety system was tested against outer magnetic perturbations, and calibrated to define a safe operation of the gradient coil. First measurements using parallel transmission were also performed on an ex-vivo brain to mitigate the RF field inhomogeneity effect.
RESULTS
Acoustics measurements show promising results with sound pressure levels slightly above the enforced limits only at certain frequency intervals. Vibrations of the gradient coil revealed a linear trend with the B field only in the worst case. Field monitoring revealed some resonances at some frequencies that are still under investigation.
DISCUSSION
Gradient-magnet interaction tests at up to 11.7 T are concluded. The scanner is now kept permanently at field and the final calibrations are on-going to pave the road towards the first acquisitions on volunteers.
Topics: Humans; Magnets; Magnetic Resonance Imaging; Magnetic Fields; Magnetics; Whole Body Imaging
PubMed: 36715884
DOI: 10.1007/s10334-023-01063-5 -
Biosensors & Bioelectronics Feb 2023The process of developing an end-to-end model of a magneto-immunoassay is described, simulating the agglutination effect due to the specific binding of bacteria to...
The process of developing an end-to-end model of a magneto-immunoassay is described, simulating the agglutination effect due to the specific binding of bacteria to paramagnetic particles. After establishing the properties of the dose-specific agglutination through direct imaging, a microfluidic assay was used to demonstrate changes in the magnetophoretic transport dynamics of agglutinated clusters via transient inductive magentometer measurements. End-to-end mathematical modelling is used to establish the physical processes underlying the assay. First, a modified form of Becker-Döring nucleation kinetic equations is used to establish a relationship between analyte dose and average cluster size. Next, Stokes flow equations are used to establish a relationship between cluster size and speed of motion within the fluid chamber. This predicts a cluster-size dynamic profile of concentration of PMPs versus time when the magnetic field is switched between the two actuated magnets. Finally, inductive modelling is carried out to predict the response of the magnetometer circuit in response to the dynamics of magnetic clusters. The predictions of this model are shown to agree well with the results of experiments, and to predict the shape of the dose-response curve.
Topics: Biosensing Techniques; Models, Theoretical; Magnetics; Magnets; Motion
PubMed: 36502714
DOI: 10.1016/j.bios.2022.114745 -
Proceedings of the Japan Academy.... 2012Various molecular magnetic compounds whose magnetic properties can be controlled by external stimuli have been developed, including electrochemically, photochemically,... (Review)
Review
Various molecular magnetic compounds whose magnetic properties can be controlled by external stimuli have been developed, including electrochemically, photochemically, and chemically tunable bulk magnets as well as a phototunable antiferromagnetic phase of single chain magnet. In addition, we present tunable paramagnetic mononuclear complexes ranging from spin crossover complexes and valence tautomeric complexes to Co complexes in which orbital angular momentum can be switched. Furthermore, we recently developed several switchable clusters and one-dimensional coordination polymers. The switching of magnetic properties can be achieved by modulating metals, ligands, and molecules/ions in the second sphere of the complexes.
Topics: Light; Magnets; Molecular Conformation; Polymerization; Quantum Theory; Stereoisomerism
PubMed: 22728438
DOI: 10.2183/pjab.88.213