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Nano Letters Dec 2022Nanometric topological spin textures, such as skyrmions (Sks) and antiskyrmions (antiSks), have attracted much attention recently. However, most studies have focused on...
Nanometric topological spin textures, such as skyrmions (Sks) and antiskyrmions (antiSks), have attracted much attention recently. However, most studies have focused on two-dimensional spin textures in films with inherent or synthetic antisymmetric spin-exchange interaction, termed Dzyaloshinskii-Moriya interaction, although three-dimensional (3D) topological spin textures, such as antiSks composed of alternating Bloch- and Néel-type spin spirals, chiral bobbers carrying emergent magnetic monopoles, and deformed Sk strings, are ubiquitous. To elucidate these textures, we have developed a 3D nanometric magnetic imaging technique, tomographic Lorentz transmission electron microscopy (TEM). The approach enables the visualization of the 3D shape of magnetic objects and their 3D vector field mapping. Here we report 3D vector field maps of deformed Sk-strings and antiSk using the technique. This research approach will lead to discoveries and understanding of fertile 3D magnetic structures in a broad class of magnets, providing insight into 3D topological magnetism.
Topics: Imaging, Three-Dimensional; Magnets; Microscopy, Electron, Transmission
PubMed: 36383503
DOI: 10.1021/acs.nanolett.2c03142 -
Cytometry. Part a : the Journal of the... Jun 2016Quantitative characterization of magnetic particles is useful for analysis and separation of labeled cells and magnetic particles. A particle velocimeter is used to...
Quantitative characterization of magnetic particles is useful for analysis and separation of labeled cells and magnetic particles. A particle velocimeter is used to directly measure the magnetophoretic mobility, size, and other parameters of magnetic particle suspensions. The instrument provides quantitative video analysis of particles and their motion. The trajectories of magnetic particles in an isodynamic magnetic field are recorded using a high-definition camera/microscope system for image collection. Image analysis software then converts the image data to the parameters of interest. The distribution of magnetophoretic mobility is determined by combining fast image analysis with velocimetry measurements. Particle size distributions have been characterized to provide a better understanding of sample quality. The results have been used in the development and operation of analyzer protocols for counting particle concentrations accurately and measuring magnetic susceptibility and size for simultaneous display for routine application to particle suspensions and magnetically labeled biological cells. © 2016 International Society for Advancement of Cytometry.
Topics: Image Processing, Computer-Assisted; Immunomagnetic Separation; Magnets; Molecular Imaging; Particle Size; Rheology; Software; Video Recording
PubMed: 27123879
DOI: 10.1002/cyto.a.22866 -
Joint Diseases and Related Surgery 2021The aim of this study was to evaluate the clinical and radiographic outcomes and complications of dual magnetically controlled growing rods (MCGRs) in the treatment of...
OBJECTIVES
The aim of this study was to evaluate the clinical and radiographic outcomes and complications of dual magnetically controlled growing rods (MCGRs) in the treatment of early-onset scoliosis (EOS) and to investigate the results of patients with definitive spinal fusion following MCGR.
PATIENTS AND METHODS
A total of 15 patients (7 males, 8 females; mean age: 8.7±1.7 years; range, 6 to 10 years) with EOS who underwent dual MCGR and were prospectively followed between February 2013 and March 2019 were included in this retrospective study. The Cobb angle, thoracic kyphosis, and the length of the spine between T1-T12 and T1-S1 were measured on preoperative, postoperative, and follow-up radiographs. The 24-Item Early-Onset Scoliosis Questionnaire (EOSQ-24) was used to assess the functional outcomes before and after the operation. All complications during the treatment were recorded.
RESULTS
The mean follow-up was 27.8±10.4 (range, 12 to 60) months. The mean curve correction immediately after the index surgery and latest follow-up was 47.6% and 42.4%, respectively (p>0.05). At the last follow-up, there were no significant changes in mean Cobb and kyphosis angles. The mean T1-T12 length increase was 26.2±7.1 (range, 16 to 40) mm, while the mean T1-S1 length increase was 43.3±15.0 (range, 24 to 70) mm. Complications developed in four (26.6%) of 15 patients. Definitive spinal fusion surgery was performed in seven patients. Total mean Cobb angle difference between the final follow-up and fusion surgery was 9.3° (p=0.016) and kyphosis angle difference was -2.1° (p=0.349). After fusion surgery, total lengthening in T1-T12 and T1-S1 distance was 10.5 mm (p=0.036) and 15.0 mm (p=0.022), respectively. A significant increase in all subdomain scores of the EOSQ-24 (p<0.05), except for financial impact, was recorded in all patients.
CONCLUSION
Dual MCGR technique is an effective, reliable, and robust treatment alternative for primary EOS. However, surgeons should be aware of the relatively high rate of complications. In addition, residual deformity can be corrected successfully with definitive surgery.
Topics: Child; Female; Humans; Internal Fixators; Magnets; Male; Postoperative Period; Radiography; Retrospective Studies; Scoliosis; Spinal Fusion; Treatment Outcome; Turkey
PubMed: 34145827
DOI: 10.52312/jdrs.2021.49 -
Academic Emergency Medicine : Official... Mar 2001To describe a novel endotracheal intubation technique, magnetically guided intubation (MGI), and its rate of success in inexperienced medical students and interns using...
OBJECTIVE
To describe a novel endotracheal intubation technique, magnetically guided intubation (MGI), and its rate of success in inexperienced medical students and interns using an airway mannequin model.
METHODS
This was a prospective, descriptive study of 25 medical students and interns participating in an introductory course on emergency medicine without prior experience in human orotracheal intubation. Magnetically guided intubation consists of a strong external magnet placed over the cricothyroid membrane to guide the introduction of a standard endotracheal tube containing a stylet with a magnetized tip. An airway mannequin was placed in a rigid cervical spinal collar to increase the difficulty of the intubation, and each student performed two sequential intubation attempts using MGI. The proportions of successful intubations and the time to complete intubation were determined. Descriptive statistics were used to describe point estimates and 95% confidence intervals for means and proportions of continuous and categorical data, respectively.
RESULTS
Of 25 participants, 19 were students and six were interns. Their mean age was 27 years, and 76% were male. The overall proportion of successful intubations using MGI was 80% (95% CI = 69% to 91%). Of 24 intubations, 48% were attempted without visualization of the vocal cords; 67% were successful (95% CI = 46% to 87%). The mean time required to complete intubation was 17.0 seconds (95% CI = 14.5 to 19.5 seconds).
CONCLUSIONS
A novel method of orotracheal intubation using magnetic guidance is described as achieving a high rate of successful intubations when performed by inexperienced intubators.
Topics: Adult; Equipment Design; Female; Humans; Intubation, Intratracheal; Magnetics; Male; Prospective Studies; Treatment Outcome
PubMed: 11229954
DOI: 10.1111/j.1553-2712.2001.tb01308.x -
Physica Medica : PM : An International... Apr 2021To investigate the displacement forces and image artifacts associated with passive medical implants for recently-developed low-field (<100 mT) MRI systems, and to...
Characterization of displacement forces and image artifacts in the presence of passive medical implants in low-field (<100 mT) permanent magnet-based MRI systems, and comparisons with clinical MRI systems.
PURPOSE
To investigate the displacement forces and image artifacts associated with passive medical implants for recently-developed low-field (<100 mT) MRI systems, and to compare these with values from higher field strengths used for clinical diagnosis.
METHODS
Setups were constructed to measure displacement forces in a permanent magnet-based Halbach array used for in vivo MRI at 50 mT, and results compared with measurements at 7 T. Image artifacts were assessed using turbo (fast) spin echo imaging sequences for four different passive medical implants: a septal occluder, iliac stent, pedicle screw and (ferromagnetic) endoscopic clip. Comparisons were made with artifacts produced at 1.5, 3 and 7 T. Finally, specific absorption rate (SAR) simulations were performed to determine under what operating conditions the limits might be approached at low-field.
RESULTS
Displacement forces at 50 mT on all but the ferromagnetic implant were between 1 and 10 mN. Image artifacts at 50 mT were much less than at clinical field strengths for all passive devices, and with the exception of the ferromagnetic clip. SAR simulations show that very long echo train (>128) turbo spin echo sequences can be run with short inter-pulse times (5-10 ms) within SAR limits.
CONCLUSIONS
This work presents the first evaluation of the effects of passive implants at field strengths less than 100 mT in terms of displacement forces, image artifacts and SAR. The results support previous claims that such systems can be used safely and usefully in challenging enviroments such as the intensive care unit.
Topics: Artifacts; Magnetic Resonance Imaging; Magnets; Prostheses and Implants
PubMed: 33894581
DOI: 10.1016/j.ejmp.2021.04.003 -
Cells Jul 2021Magnetophoresis-based microfluidic devices offer simple and reliable manipulation of micro-scale objects and provide a large panel of applications, from selective...
Magnetophoresis-based microfluidic devices offer simple and reliable manipulation of micro-scale objects and provide a large panel of applications, from selective trapping to high-throughput sorting. However, the fabrication and integration of micro-scale magnets in microsystems involve complex and expensive processes. Here we report on an inexpensive and easy-to-handle fabrication process of micrometer-scale permanent magnets, based on the self-organization of NdFeB particles in a polymer matrix (polydimethylsiloxane, PDMS). A study of the inner structure by X-ray tomography revealed a chain-like organization of the particles leading to an array of hard magnetic microstructures with a mean diameter of 4 µm. The magnetic performance of the self-assembled micro-magnets was first estimated by COMSOL simulations. The micro-magnets were then integrated into a microfluidic device where they act as micro-traps. The magnetic forces exerted by the micro-magnets on superparamagnetic beads were measured by colloidal probe atomic force microscopy (AFM) and in operando in the microfluidic system. Forces as high as several nanonewtons were reached. Adding an external millimeter-sized magnet allowed target magnetization and the interaction range to be increased. Then, the integrated micro-magnets were used to study the magnetophoretic trapping efficiency of magnetic beads, providing efficiencies of 100% at 0.5 mL/h and 75% at 1 mL/h. Finally, the micro-magnets were implemented for cell sorting by performing white blood cell depletion.
Topics: Cell Separation; Humans; Immunomagnetic Separation; Lab-On-A-Chip Devices; Leukocytes; Magnetics; Microtechnology; Polymers; Tomography, X-Ray
PubMed: 34359904
DOI: 10.3390/cells10071734 -
Journal of Prosthodontic Research Jul 2022To assess the bonding between conventional and additively manufactured silicone elastomers and cylindrical retention titanium magnets for anchorage of facial prostheses.
PURPOSE
To assess the bonding between conventional and additively manufactured silicone elastomers and cylindrical retention titanium magnets for anchorage of facial prostheses.
METHODS
The customized titanium retention magnets were embedded in conventional and additively produced silicone blocks without primer application (n = 20) and with two commercially available primers G611 (n = 20) and A304 (n = 20) applied onto the magnet surface. The pull out test was performed in the universal testing machine using 45° and 90° angulation and the pull out strength was measured for each group. Additionally the SEM images of the pulled out magnets' surface were obtained and the amount of residual silicone onto the magnet surface was quantified.
RESULTS
Significantly higher pull out strength values (p < 0.05) were revealed for 90° specimens (0.11 - 0.17 ± 0.01 N/mm) compared to the 45° group (0.03 ± 0.02 N/mm). The pull out test with primer revealed no significant differences between the G 611 and A 304 primers in the additive group. However, significantly (p < 0,05) higher values were observed for conventional specimens in the A304 group (1.10 ± 0.21 N/mm) compared to the G611 group (0.59 ± 0.27 N/mm).
CONCLUSION
The application of both used primers may be an acceptable technical option for the anchorage of retention titanium magnets in silicone facial prostheses, produced additively in a fully digital workflow.
Topics: Magnets; Materials Testing; Maxillofacial Prosthesis; Printing, Three-Dimensional; Silicone Elastomers; Titanium
PubMed: 34545007
DOI: 10.2186/jpr.JPR_D_21_00019 -
Scientific Reports Aug 2018Rats are suitable animal models in which to study the effects of gastric bypass surgery. However, construction of gastrojejunal anastomosis in the rat is technically...
Rats are suitable animal models in which to study the effects of gastric bypass surgery. However, construction of gastrojejunal anastomosis in the rat is technically demanding and is associated with high rate of postoperative complications. The aim of this study was to explore the feasibility and efficacy of the magnetic compression technique (MCT) in side-to-side gastrojejunal anastomosis in rats. Thirty male rats underwent gastrojejunal anastomosis using one of three techniques: hand-sewn, magnetic compression using cuboid magnets, and magnetic compression using magnetic rings. The mean anastomosis time using the magnetic compression technique was significantly less than that of the hand-sewn technique (3.6 ± 0.96 and 6.50 ± 1.58 vs. 14.40 ± 2.37 minutes,). The survival rate was highest in animals treated with magnetic compression using cuboid magnets (100%), followed by animals treated with magnetic compression using magnetic rings (90%) and then hand sewing (70%). The mean burst pressure did not differ significantly between the magnetic compression and hand-sewn anastomoses. Anastomoses constructed by magnetic compression were smoother and flatter than hand-sewn anastomoses. The results showed that MCT is a simple and feasible method for gastrojejunal anastomosis in the rat.
Topics: Anastomosis, Surgical; Animals; Gastric Bypass; Jejunum; Magnetics; Magnets; Male; Rats; Rats, Sprague-Dawley; Stomach
PubMed: 30072707
DOI: 10.1038/s41598-018-30075-8 -
Journal of the American Chemical Society Dec 2022The study of how spin interacts with lattice vibrations and relaxes to equilibrium provides unique insights into its chemical environment and the relation between...
The study of how spin interacts with lattice vibrations and relaxes to equilibrium provides unique insights into its chemical environment and the relation between electronic structure and molecular composition. Despite its importance for several disciplines, ranging from magnetic resonance to quantum technologies, a convincing interpretation of spin dynamics in crystals of magnetic molecules is still lacking due to the challenging experimental determination of the correct spin relaxation mechanism. We apply spin dynamics to a series of 12 coordination complexes of Co and Dy ions selected among ∼240 compounds that largely cover the literature on single-molecule magnets and well represent different regimes of spin relaxation. Simulations reveal that the Orbach spin relaxation rate of known compounds mostly depends on the ions' zero-field splitting and little on the details of molecular vibrations. Raman relaxation is instead found to be also significantly affected by the features of low-energy phonons. These results provide a complete understanding of the factors limiting spin lifetime in single-molecule magnets and revisit years of experimental investigations by making it possible to transparently distinguish Orbach and Raman relaxation mechanisms.
Topics: Magnets; Technology; Coordination Complexes; Electronics; Vibration
PubMed: 36490388
DOI: 10.1021/jacs.2c08876 -
Nature Apr 2015Fluorescent and plasmonic labels and sensors have revolutionized molecular biology, helping visualize cellular and biomolecular processes. Increasingly, such probes are...
Fluorescent and plasmonic labels and sensors have revolutionized molecular biology, helping visualize cellular and biomolecular processes. Increasingly, such probes are now being designed to respond to wavelengths in the near-infrared region, where reduced tissue autofluorescence and photon attenuation enable subsurface in vivo sensing. But even in the near-infrared region, optical resolution and sensitivity decrease rapidly with increasing depth. Here we present a sensor design that obviates the need for optical addressability by operating in the nuclear magnetic resonance (NMR) radio-frequency spectrum, where signal attenuation and distortion by tissue and biological media are negligible, where background interferences vanish, and where sensors can be spatially located using standard magnetic resonance imaging (MRI) equipment. The radio-frequency-addressable sensor assemblies presented here comprise pairs of magnetic disks spaced by swellable hydrogel material; they reversibly reconfigure in rapid response to chosen stimuli, to give geometry-dependent, dynamic NMR spectral signatures. The sensors can be made from biocompatible materials, are themselves detectable down to low concentrations, and offer potential responsive NMR spectral shifts that are close to a million times greater than those of traditional magnetic resonance spectroscopies. Inherent adaptability should allow such shape-changing systems to measure numerous different environmental and physiological indicators, thus providing broadly generalizable, MRI-compatible, radio-frequency analogues to optically based probes for use in basic chemical, biological, medical and engineering research.
Topics: Animals; Biocompatible Materials; Biofouling; Cells; Colorimetry; Dogs; Hydrogels; Hydrogen-Ion Concentration; Ions; Madin Darby Canine Kidney Cells; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Magnetics; Magnets; Molecular Probes; Nanostructures; Radio Waves; Spatio-Temporal Analysis
PubMed: 25778701
DOI: 10.1038/nature14294