A new mouse model of ankle instability induced by multiple mechanical sprains with controlled inversion angle and speed.

Ankle sprain occurs by a sudden and extreme inversion and plantarflexion at the ankle joint to cause ligamentous injuries. A portion of ankle sprain patients experience recurrent ankle sprains and develop chronic ankle instability (CAI). The present CAI animal models are single events with severe ligamentous injury using surgical transection of ligaments or manually overextending the ankle. Purpose: To simulate the mechanical and recurrent sprain injuries in CAI patients, we established a new ankle instability model with multiple ankle injuries using a self-designed machine to sprain the ankle with a controlled inversion angle and speed. Methods: Male C57BL/6J mice were used and respectively subjected to a sham operation, calcaneofibular ligament (CFL) transection, and mechanical ankle sprains. Three mechanical sprains were performed on the 13th and 185th day after the initial mechanical ankle sprain. Results: The first mechanical sprain and CFL transection induced ankle injury as indicated by an average of a 62% decrease in ankle pressure pain threshold and a 114% increase in the ankle thickness compared with the contralateral untreated ankle. The second and third mechanical sprains induced recurrent ankle injuries. The foot slips during beam tests were increased after mechanical ankle sprains but not after CFL transection, indicating the induction of motor balance deficits. Multiple mechanical ankle sprains induced significant gait changes in longer duration of stance (an average of 194% increase), swing (134%), and step cycle (147%) compared with CFL transection or sham operation, and slower walking speed (78% reduction) and shorter step distance (91%) after the third sprain. Conclusion: These results elucidate that multiple mechanical sprains, which induce recurrent ankle injuries, balance deficits, and gait changes, are a good model for investigating the mechanisms of CAI induced by recurrent sprain injuries.

Influence of Y Doping on WO3 Membranes Applied in Electrolyte-Insulator-Semiconductor Structures.

In this paper, tungsten oxide (WO3) is deposited on a silicon substrate applied in electrolyte-insulator-semiconductor structures for pH sensing devices. To boost the sensing performance, yttrium (Y) is doped into WO3 membranes, and annealing is incorporated in the fabrication process. To investigate the effects of Y doping and annealing, multiple material characterizations including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atom force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are performed. Material analysis results indicate that annealing and Y doping can increase crystallinity, suppress defects, and enhance grainization, thereby strengthening membrane sensing capabilities in terms of sensitivity, linearity, and reliability. Because of their stable response, high reliability, and compact size, Y-doped WO3 membranes are promising for future biomedical applications.

Bipolar Electric-Field Switching of Perpendicular Magnetic Tunnel Junctions through Voltage-Controlled Exchange Coupling.

Perpendicular magnetic tunnel junctions (p-MTJs) switched utilizing bipolar electric fields have extensive applications in energy-efficient memory and logic devices. Voltage-controlled magnetic anisotropy linearly lowers the energy barrier of the ferromagnetic layer via the electric field effect and efficiently switches p-MTJs only with a unipolar behavior. Here, we demonstrate a bipolar electric field effect switching of 100 nm p-MTJs with a synthetic antiferromagnetic free layer through voltage-controlled exchange coupling (VCEC). The switching current density, ∼1.1 × 105 A/cm2, is 1 order of magnitude lower than that of the best-reported spin-transfer torque devices. Theoretical results suggest that the electric field induces a ferromagnetic-antiferromagnetic exchange coupling transition of the synthetic antiferromagnetic free layer and generates a fieldlike interlayer exchange coupling torque, which causes the bidirectional magnetization switching of p-MTJs. These results could eliminate the major obstacle in the development of spin memory devices beyond their embedded applications.

Understanding the Switching Mechanisms of the Antiferromagnet/Ferromagnet Heterojunction.

Electric-field-driven spintronic devices are considered promising candidates for beyond CMOS logic and memory applications thanks to their potential for ultralow energy switching and nonvolatility. In this work, we have developed a comprehensive modeling framework to understand the fundamental physics of the switching mechanisms of the antiferromagnet/ferromagnet heterojunction by taking BiFeO3/CoFe heterojunctions as an example. The models are calibrated with experimental results and demonstrate that the switching of the ferromagnet in the antiferromagnet/ferromagnet heterojunction is caused by the rotation of the Neel vector in the antiferromagnet and is not driven by the unidirectional exchange bias at the interface as was previously speculated. Additionally, we demonstrate that the fundamental limit of the switching time of the ferromagnet is in the subnanosecond regime. The geometric dependence and the thermal stability of the antiferromagnet/ferromagnet heterojunction are also explored. Our simulation results provide the critical metrics for designing magnetoelectric devices.

Cold Exposure After Exercise Impedes the Neuroprotective Effects of Exercise on Thermoregulation and UCP4 Expression in an MPTP-Induced Parkinsonian Mouse Model.

Moderate exercise and mild hypothermia have protective effects against brain injury and neurodegeneration. Running in a cold environment alters exercise-induced hyperthermia and outcomes; however, evaluations of post-exercise cold exposure related to exercise benefits for the brain are relatively rare. We investigated the effects of 4°C cold exposure after exercise on exercise-induced thermal responses and neuroprotection in an MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced Parkinsonian mouse model. Male C57BL/6J mice were pretreated with MPTP for five consecutive days and follow-up treadmill exercise for 4 weeks. After 1-h running at a 22°C temperature, the mice were exposed to a 4°C environment for 2 h. An MPTP injection induced a transient drop in body and brain temperatures, while mild brain hypothermia was found to last for 4 weeks after MPTP treatment. Preventing brain hypothermia by exercise or 4°C exposure was associated with an improvement in MPTP-induced striatal uncoupling protein 4 (UCP4) downregulation and nigrostriatal dopaminergic neurodegeneration. However, 4°C exposure after exercise abrogated the exercise-induced beneficial effects and thermal responses in MPTP-treated mice, including a low amplitude of exercise-induced brain hyperthermia and body temperature while at rest after exercise. Our findings elucidate that post-exercise thermoregulation and UCP4 expression are important in the neuroprotective effects of exercise against MPTP toxicity.

Rab11 activation by Ik2 kinase is required for dendrite pruning in Drosophila sensory neurons.

Neuronal pruning is a commonly observed phenomenon for the developing nervous systems to ensure precise wiring of neural circuits. The function of Ik2 kinase and its downstream mediator, Spindle-F (Spn-F), are essential for dendrite pruning of Drosophila sensory neurons during development. However, little is known about how Ik2/Spn-F signaling is transduced in neurons and ultimately results in dendrite pruning. Our genetic analyses and rescue experiments demonstrated that the small GTPase Rab11, especially the active GTP-bound form, is required for dendrite pruning. We also found that Rab11 shows genetic interactions with spn-F and ik2 on pruning. Live imaging of single neurons and antibody staining reveal normal Ik2 kinase activation in Rab11 mutant neurons, suggesting that Rab11 could have a functional connection downstream of and/or parallel to the Ik2 kinase signaling. Moreover, we provide biochemical evidence that both the Ik2 kinase activity and the formation of Ik2/Spn-F/Rab11 complexes are central to promote Rab11 activation in cells. Together, our studies reveal that a critical role of Ik2/Spn-F signaling in neuronal pruning is to promote Rab11 activation, which is crucial for dendrite pruning in neurons.

The adsorption kinetics of a fluorinated surfactant--heptadecafluoro-1-nonanol.

The adsorption kinetics of heptadecafluoro-1-nonanol (C8F17CH2OH) onto a clean air-water interface were studied. Video-enhanced pendant (emerging) bubble tensiometry was employed to measure the equation of state and the dynamic/equilibrium surface tensions. Relaxation profiles of the surface tension for heptadecafluoro-1-nonanol molecules absorbing onto a freshly created air-water interface were obtained and simulated from theory. The adsorption of the fluoroalcohol C8F17CH2OH was found to be cooperative from the comparison of the equilibrium surface tension data at γ(C)>65 mN/m to the prediction of the Frumkin model. The comparison was made for the entire relaxation period of the tension data and the model predictions. The controlling mechanism of the adsorption process was found to be mixed diffusive-kinetic control. Values of the adsorption/desorption rate constants of C8F17CH2OH were estimated from these dynamic surface tension profiles with a diffusivity of 5.93×10(-6) cm(2)/s, which was evaluated from the Wilke-Chang equation for C8F17CH2OH.