Магнитные состояния в модели поверхностного димера

For the electrons of surface dimer formed by adsorbed particle and substrate atom effects of the intra- and interatomic Coulomb interactions are taken into account. Two cases are considered: adsorption of magnetic particle on nonmagnetic substrate and adsorption of nonmagnetic particle on magnetic substrate. Analytical expressions for the surface dimer magnetization are obtained for the regimes of weak and strong dimer – substrate coupling

2021 Revisions to ASTM E1417/E1417M and E1444/E1444M

This article provides an overview of the 2021 revisions to the industry standards for aerospace liquid penetrant and magnetic particle inspections, ASTM E1417/1417M and ASTM E1444/E1444M.

Magnetic particle imaging: tracer development and the biomedical applications of a radiation-free, sensitive, and quantitative imaging modality

Magnetic particle imaging (MPI) is an emerging tracer-based modality that enables real-time three-dimensional imaging of the non-linear magnetisation produced by superparamagnetic iron oxide nanoparticles (SPIONs), in the presence of an...

Sensitive and Specific Detection of Breast Cancer Lymph Node Metastasis Through Dual-Modality Magnetic Particle Imaging and Fluorescence Molecular Imaging: a Preclinical Evaluation

Purpose: A sensitive and specific imaging method to detect metastatic cancer cells in lymph nodes (LNs) to detect the early-stage breast cancer is urgently needed. The purpose of this study was to investigate a novel breast cancer-targeting and tumour microenvironment ATP-responsive superparamagnetic iron oxide (SPIOs) imaging probe that was developed to detect lymph node metastasis (LNMs) through fluorescence molecular imaging (FMI) and magnetic particle imaging (MPI). The imaging nanoprobe comprised of SPIOs conjugated with breast cancer-targeting peptides (CREKA) and an ATP-responsive DNA aptamer (dsDNA-Cy5.5), abbreviated as SPIOs@A-T. Methods: SPIOs@A-T was synthesised and characterized for its imaging properties, targeting ability and toxicity in vitro. Mice with metastatic lymph node (MLN) of breast cancer were established to evaluate the FMI and MPI imaging strategy in vivo. Healthy mice with normal lymph node (NLN) were used as control group. Histological examination and biosafety evaluation were performed for further assessment. Results: After injection with SPIO@A-T, the obvious high fluorescent intensity and MPI signal were observed in MLN group than those in NLN group. MPI could also complement the limitation of imaging depth from FMI, thus could detect MLN more sensitively. The combination of the imaging strengths of FMI and MPI ensured the detection of breast cancer metastases with high sensitivity and specificity, thereby facilitating the precision differentiation of malignant from benign LNs. Besides, the biosafety evaluation results showed SPIO@A-T had good biocompatibility. Conclusion: Due to the superior properties of tumour-targeting, detection specificity, and biosafety, the SPIOs@A-T imaging probe in combination with FMI and MPI can provide a promising novel method for the early and precise detection of LNMs in clinical practice.

Modelling of Dynamic Behaviour in Magnetic Nanoparticles

The efficient development and utilisation of magnetic nanoparticles (MNPs) for applications in enhanced biosensing relies on the use of magnetisation dynamics, which are primarily governed by the time-dependent motion of the magnetisation due to externally applied magnetic fields. An accurate description of the physics involved is complex and not yet fully understood, especially in the frequency range where Néel and Brownian relaxation processes compete. However, even though it is well known that non-zero, non-static local fields significantly influence these magnetisation dynamics, the modelling of magnetic dynamics for MNPs often uses zero-field dynamics or a static Langevin approach. In this paper, we developed an approximation to model and evaluate its performance for MNPs exposed to a magnetic field with varying amplitude and frequency. This model was initially developed to predict superparamagnetic nanoparticle behaviour in differential magnetometry applications but it can also be applied to similar techniques such as magnetic particle imaging and frequency mixing. Our model was based upon the Fokker–Planck equations for the two relaxation mechanisms. The equations were solved through numerical approximation and they were then combined, while taking into account the particle size distribution and the respective anisotropy distribution. Our model was evaluated for Synomag®-D70, Synomag®-D50 and SHP-15, which resulted in an overall good agreement between measurement and simulation.

Magnetic particle-antiparticle creation and annihilation

A fundamental property of particles and antiparticles, such as electrons and positrons, is their ability to annihilate one another. Similar behavior is predicted for magnetic solitons~\cite{Kovalev_90}-- localized spin textures that can be distinguished by their topological index Q.Theoretically, magnetic topological solitons with opposite values of Q, such as skyrmions~\cite{Bogdanov_89} and their antiparticles -- antiskyrmions -- are expected to be able to merge continuously and to annihilate~\cite{Kuchkin_20i}. However, experimental verification of such particle-antiparticle pair production and annihilation processes has been lacking. Here, we report the creation and annihilation of skyrmion-antiskyrmion pairs in an exceptionally thin film of the cubic chiral magnet B20-type FeGe observed using transmission electron microscopy. Our observations are highly reproducible and are fully consistent with micromagnetic simulations. Our findings provide a new platform for fundamental studies of particles and antiparticles based on magnetic solids and open new perspectives for practical applications of thin films of isotropic chiral magnets.