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Diffusion MRI may enable non-invasive mapping of axonal microstructure. Most approaches infer axon diameters from effects of time-dependent diffusion on the diffusion-weighted MR signal by modelling axons as straight cylinders. Axons do…

Medical Physics · Physics 2019-03-13 Jan Brabec , Samo Lasic , Markus Nilsson

During the first years of life, the human brain undergoes dynamic spatially-heterogeneous changes, involving differentiation of neuronal types, dendritic arborization, axonal ingrowth, outgrowth and retraction, synaptogenesis, and…

Abstract We study the temperature dependence of the absorption of microwaves by random-anisotropy magnets. It is governed by strong metastability due to the broad distribution of energy barriers separating different spin configurations. At…

Materials Science · Physics 2025-02-14 D. A. Garanin , E. M. Chudnovsky

The geometry of mesoscopic inhomogeneities plays an important role in determining the macroscopic propagation behaviors of elastic waves in a heterogeneous medium. Nonequiaxed inhomogeneities can lead to anisotropic wave velocity and…

Geophysics · Physics 2020-05-05 Huijing He

In biological tissue, MR transverse relaxation stems from mechanisms spanning multiple scales, from molecular dipole-dipole interactions to mesoscopic field variations driven by tissue microstructure. While mesoscopic relaxation reflects…

A new theory is developed for the magnetoelectric (ME) coupling in a symmetric 2-2 ME laminate having a representative piezoelectric crystal (PMN-PT) particularly with anisotropic piezoelectric properties. Considering the average field…

We review, systematize and discuss models of diffusion in neuronal tissue, by putting them into an overarching physical context of coarse-graining over an increasing diffusion length scale. From this perspective, we view research on…

Biological Physics · Physics 2018-04-20 Dmitry S. Novikov , Els Fieremans , Sune N. Jespersen , Valerij G. Kiselev

Diffusion-attenuated MR signal for heterogeneous media has been represented as a sum of signals from anisotropic Gaussian sub-domains. Any effect of macroscopic (global or ensemble) anisotropy in the signal can be removed by averaging the…

Applied Physics · Physics 2020-01-03 Magnus Herberthson , Cem Yolcu , Hans Knutsson , Carl-Fredrik Westin , Evren Özarslan

Periodic structures can be engineered to exhibit unique properties observed at symmetry points, such as zero group velocity, Dirac cones and saddle points; identifying these, and the nature of the associated modes, from a direct reading of…

Early diagnosis and noninvasive monitoring of neurological disorders require sensitivity to elusive cellular-level alterations that occur much earlier than volumetric changes observable with the millimeter-resolution of medical imaging…

Transition metal ferromagnetic films with perpendicular magnetic anisotropy (PMA) have ferromagnetic resonance (FMR) linewidths that are one order of magnitude larger than soft magnetic materials, such as pure iron (Fe) and permalloy (NiFe)…

Materials Science · Physics 2009-12-14 J-M. Beaujour , D. Ravelosona , I. Tudosa , E. Fullerton , A. D. Kent

When magnetohydrodynamic turbulence evolves in the presence of a large-scale mean magnetic field, an anisotropy develops relative to that preferred direction. The well-known tendency is to develop stronger gradients perpendicular to the…

Plasma Physics · Physics 2020-07-15 Rohit Chhiber , William H. Matthaeus , Sean Oughton , Tulasi N. Parashar

Microscopic model of the interaction of spins with a microwave field in a random-anisotropy magnet has been developed. Numerical results show that microwave absorption occurs in a broad range of frequencies due to the distribution of…

Materials Science · Physics 2021-06-09 D. A. Garanin , E. M. Chudnovsky

Diffusion Magnetic Resonance Imaging (dMRI) is an imaging technique with exquisite sensitivity to the microstructural properties of heterogeneous media. The conventionally adopted acquisition schemes involving single pulsed field gradients…

Biological Physics · Physics 2023-01-04 Deneb Boito , Cem Yolcu , Evren Özarslan

We propose a new model to describe diffusion processes within active deformable media. Our general theoretical framework is based on physical and mathematical considerations, and it suggests to use diffusion tensors directly coupled to…

Tissues and Organs · Quantitative Biology 2021-03-03 Christian Cherubini , Simonetta Filippi , Alessio Gizzi , Ricardo Ruiz-Baier

We investigate the occurrence of anomalous diffusive transport associated with acoustic wave fields propagating through highly-scattering periodic media. Previous studies had correlated the occurrence of anomalous diffusion to either the…

Disordered Systems and Neural Networks · Physics 2019-03-27 Salvatore Buonocore , Mihir Sen , Fabio Semperlotti

Diffusion models trained on different, non-overlapping subsets of a dataset often produce strikingly similar outputs when given the same noise seed. We trace this consistency to a simple linear effect: the shared Gaussian statistics across…

Machine Learning · Computer Science 2026-02-04 Binxu Wang , Jacob Zavatone-Veth , Cengiz Pehlevan

Anisotropic diffusion is one of the potential interpretations for the morphology of the Geminga pulsar halo. It interprets the observed slow-diffusion phenomenon through a geometric effect, assuming the mean magnetic field direction around…

High Energy Astrophysical Phenomena · Physics 2023-08-02 Kun Fang , Hong-Bo Hu , Xiao-Jun Bi , En-Sheng Chen

Diffusion of particles has wide repercussions ranging from particle-based soft matter systems to solid state systems with particular electronic properties. Recently, in the field of magnetism, diffusion of magnetic skyrmions, topologically…

We develop an analytical approach for studying the FMR frequency shift due to dipolar interactions and surface effects in two-dimensional arrays of nanomagnets with (effective) uniaxial anisotropy along the magnetic field. For this we build…

Mesoscale and Nanoscale Physics · Physics 2018-06-11 J. -L. Déjardin , A. F. Franco , F. Vernay , H. Kachkachi