465 research outputs found
COMPARISON OF ELBOW ANGLES IN GYMNASTS WITH AND WITHOUT CHRONIC ELBOW PAIN IN HORSE VAULT ROUTINE
INTRODUCTION: Chronic elbow strain is an injury involving inflammation or fracture which is caused by repeated bending, stretching or rotating of the elbow over along period of time, or by squeezing from external force. When the athlete performs a vault dismount, the external force passes through his/her hands to the elbows, causing variations in elbow position.
Therefore, the action of the elbow is crucial to vault routine. When the incorrect or irregular movement of elbows repeated again and again, it might cause chronic elbow strain. The purpose of this study was to identify the relationship between elbow angle and elbow strain when performing two major movements in vault
Current-Induced Dynamics and Chaos of Antiferromagnetic Bimerons
A magnetic bimeron is a topologically non-trivial spin texture carrying an
integer topological charge, which can be regarded as the counterpart of
skyrmion in easy-plane magnets. The controllable creation and manipulation of
bimerons are crucial for practical applications based on topological spin
textures. Here, we analytically and numerically study the dynamics of an
antiferromagnetic bimeron driven by a spin current. Numerical simulations
demonstrate that the spin current can create an isolated bimeron in the
antiferromagnetic thin film via the damping-like spin torque. The spin current
can also effectively drive the antiferromagnetic bimeron without a transverse
drift. The steady motion of an antiferromagnetic bimeron is analytically
derived and is in good agreement with the simulation results. Also, we find
that the alternating-current-induced motion of the antiferromagnetic bimeron
can be described by the Duffing equation due to the presence of the nonlinear
boundary-induced force. The associated chaotic behavior of the bimeron is
analyzed in terms of the Lyapunov exponents. Our results demonstrate the
inertial dynamics of an antiferromagnetic bimeron, and may provide useful
guidelines for building future bimeron-based spintronic devices.Comment: 6 pages, 4 figure
Coercivity Mechanisms of Single-Molecule Magnets
Magnetic hysteresis has become a crucial aspect for characterizing
single-molecule magnets, but the comprehension of the coercivity mechanism is
still a challenge. By using analytical derivation and quantum dynamical
simulations, we reveal fundamental rules that govern magnetic relaxation of
single molecule magnets under the influence of external magnetic fields, which
in turn dictates the hysteresis behavior. Specifically, we find that energy
level crossing induced by magnetic fields can drastically increase the
relaxation rate and set a coercivity limit. The activation of
optical-phonon-mediated quantum tunneling accelerates the relaxation and
largely determines the coercivity. Intra-molecular exchange interaction in
multi-ion compounds may enhance the coercivity by suppressing key relaxation
processes. A single-occupant bond in mixed-valence complexes compromises
coercivity, and pre-spin-flip of the bonding electron facilitates the overall
magnetization reversal. Underlying these properties are magnetic relaxation
processes modulated by the interplay of magnetic fields, phonon spectrum and
spin state configuration, which also proposes a fresh perspective for the
nearly centurial coercive paradox.Comment: 18 pages, 3 figure
Current-driven skyrmionium in a frustrated magnetic system
Magnetic skyrmionium can be used as a nanometer-scale non-volatile
information carrier, which shows no skyrmion Hall effect due to its special
structure carrying zero topological charge. Here, we report the static and
dynamic properties of an isolated nanoscale skyrmionium in a frustrated
magnetic monolayer, where the skyrmionium is stabilized by competing
interactions. The frustrated skyrmionium has a size of about nm, which can
be further reduced by tuning perpendicular magnetic anisotropy or magnetic
field. It is found that the nanoscale skyrmionium driven by the damping-like
spin-orbit torque shows directional motion with a favored Bloch-type helicity.
A small driving current or magnetic field can lead to the transformation of an
unstable N\'eel-type skyrmionium to a metastable Bloch-type skyrmionium. A
large driving current may result in the distortion and collapse of the
Bloch-type skyrmionium. Our results are useful for the understanding of
frustrated skyrmionium physics, which also provide guidelines for the design of
spintronic devices based on topological spin textures.Comment: 5 pages, 5 figure
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