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

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 $10$ 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

Spin torque nano-oscillators based on antiferromagnetic skyrmions

Skyrmion-based spin torque nano-oscillators are potential next-generation microwave signal generators. However, ferromagnetic skyrmion-based spin torque nano-oscillators cannot reach high oscillation frequencies. In this work, we propose to use the circular motion of an antiferromagnetic skyrmion to create the oscillation signal in order to overcome this obstacle. Micromagnetic simulations demonstrate that the antiferromagnetic skyrmion-based spin torque nano-oscillators can produce high frequencies (tens of GHz). Furthermore, the speed of the circular motion for an antiferromagnetic skyrmion in a nanodisk is analytically derived, which agrees well with the results of numerical simulations. Our findings are useful for the understanding of the inertial dynamics of an antiferromagnetic skyrmion and the development of future skyrmion-based spin torque nano-oscillators.Comment: 17 pages, 3 figure

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

Extracción de homogeneizado de fenoles totales del rizoma de Nelumbo nucifera y evaluación de actividades antioxidantes

This study applied the homogenate extraction method to extract total phenols (TP) from Nelumbo nucifera rhizome, and evaluated the antioxidant activities of TP. After the single-factor experiments and optimization using response surface methodology, the optimized homogenate extraction parameters for obtaining TP from Nelumbo nucifera rhizome were as follows: ethanol concentration, 37%; liquid-material ratio, 15 mL/g; extraction time, 27 s. With these conditions, the TP yield was 0.36 ± 0.04%. When the concentration was 30 mg/mL, the 2,2-diphenyl-1-(2,4,6-trinitrophenyl)-hydrazyl and hydroxyl radical scavenging rates of TP were 80.15 ± 5.12% and 67.88 ± 6.34%, respectively. Compared with the traditional extraction, the homogenate extraction has the higher TP yield and shorter extraction time. In addition, the TP obtained by homogenate extraction have the higher antioxidant activities than traditional extraction. To sum up, the homogenate extraction is an efficient and rapid method for extracting TP from Nelumbo nucifera rhizome.Este estudio aplicó el método de extracción homogeneizada para extraer fenoles totales (TP) del rizoma de Nelumbo nucifera y evaluó las actividades antioxidantes de los TP. Después de realizar experimentos de un solo factor y optimizar utilizando metodología de superficie de respuesta, los parámetros optimizados para la extracción homogeneizada de TP del rizoma de Nelumbo nucifera fueron los siguientes: concentración de etanol, 37%; relación líquido-material, 15 mL/g; tiempo de extracción, 27 s. Con estas condiciones, el rendimiento de TP fue del 0.36 ± 0.04%. Cuando la concentración fue de 30 mg/mL, las tasas de eliminación de radicales 2,2-difenil-1-(2,4,6-trinitrofenil)-hidrazilo y radicales hidroxilos fueron del 80.15 ± 5.12% y 67.88 ± 6.34%, respectivamente. En comparación con la extracción tradicional, la extracción homogeneizada mostró un mayor rendimiento de TP y un tiempo de extracción más corto. Además, los TP obtenidos mediante extracción por homogeneizado presentaron actividades antioxidantes superiores a las obtenidas por extracción tradicional. En resumen, la extracción homogeneizada es un método eficiente y rápido para extraer TP del rizoma de Nelumbo nucifera

A study of the dual-target corporate environmental behavior (DTCEB) of heavily polluting enterprises under different environment regulations: Green innovation vs. pollutant emissions

Green innovation and pollutant emissions are currently among the hottest topics in corporate environmental behavior (CEB) research. However, a few previous studies have examined these two concepts together at the choice level of CEB. This paper discusses the internal selection logic of CEB by using multinomial logit (MNL) models that consider the choices of enterprises in green innovation and illegal emissions, both across China and separately in different regions. The objective of this paper is to consider the four choices available to heavily polluting enterprises’ dual-target corporate environmental behavior (DTCEB), including alienated, conservative, contradictory, and intimate environmental behaviors. The results of this study show that, under various external pressures, 61.2% of heavily polluting enterprises choose conservative environmental behavior. There is also generally a lack of synchronization between the goals of short-term economic and long-term social benefits. At the current stage, environmental regulation measures should focus on guiding enterprises to change from alienated, conservative, and contradictory behaviors, to intimate. Instead of only focusing on monitoring pollution emissions, the government should focus on green innovation guidance to effectively promote the transformation and upgrading of heavily polluting enterprises. A moderate adjustment of the intensity of command regulation may lead to better regulatory effects. Specifically, the enforcement of laws across China should be slowed; efforts should be made to increase the focus of public participation in the eastern region; the importance of incentive-based tax rate preferences should be increased in the central region, and the intensity of legislation should be strengthened in the western region. Compared with the emphasis on environmental performance in other literature, this article uses comparative thinking to explore the choice logic of the DTCEBs, which attaches different degrees of importance to long-term social benefits and short-term economic benefits

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

Strong Gravitational Lensing in the Einstein-Proca Theory

Adopting the strong field limit approach, we investigate the strong gravitational lensing of a spherically symmetric spacetime in the Einstein-Proca theory. With the strong field limit coefficient, three observable quantities are obtained, which are the innermost relativistic image, the deflection angle and the ratio of the flux. Comparing the observable value and the theoretical value of the strong gravitational lensing, we can verify the effectiveness of the strong gravitational lensing model.Comment: 11 pages. arXiv admin note: substantial text overlap with arXiv:1506.0841