Micropillar compression of anisotropic Al2O3-based eutectic composite

Please click Additional Files below to see the full abstract

Evaluation of explosive strength ability of the upper body for athletic throwers

Physical fitness evaluation of throwing athletes has been performed based on measurement items for the purpose of power evaluation of the lower limbs and whole body; however, the method for assessing the muscle strength and exertion of the upper body has not been acknowledged extensively. The purpose of this study was to examine the effectiveness of the evaluation of the explosive muscle performance of the upper body of an athlete using several measurement parameters, including push up jump (PJ), countermovement push up (CMPU) flight time, medicine ball throw (MBT), countermovement medicine ball throw, and one repetition maximum of the bench press (BP-1RM). The relationship between these measurement items and athletic performance as determined using the IAAF score was examined. Eleven male athletes training on a daily basis were enrolled. A significant positive correlation between MBT and athletic performance was observed, indicating the usefulness of physical fitness evaluation in athletes. Conversely, PJ and CMPU were not associated with athletic performance, suggesting that these parameters may be negatively affected by the subject’s weight. Further, BP-1RM did not show a significant correlation with athletic performance, owing to the fact that the exertion characteristics of one repetition maximum do not reflect the shrinkage rate of the muscle required for throwing. It is recommended that athletes select an event wherein their weight positively affects the competitive ability and does not affect measurement parameters. Further, explosive muscle performance without counter movements maybe incorporated into the physical fitness assessment of athletes

Multiple amplitude modes in strongly coupled phonon-mediated superconductors

We study collective amplitude modes of the superconducting order parameter in strongly coupled electron-phonon systems described by the Holstein model using the nonequilibrium dynamical mean-field theory with the self-consistent Migdal approximation as an impurity solver. The frequency of the Higgs amplitude mode is found to coincide with the superconducting gap even in the strongly coupled (beyond BCS) regime. Besides the Higgs mode, we find another collective mode involving the dynamics of both the phonons and the superconducting order parameter. The frequency of this mode, higher than twice the renormalized phonon frequency in the superconducting phase, is shown to reflect a strong electron-mediated phonon-phonon interaction. Both of collective modes are predicted to contribute to time-resolved photoemission spectra after a strong laser pump as vertex corrections to produce resonance peaks, which allows one to distinguish them from quasiparticle excitations

Interaction quench in the Holstein model: Thermalization crossover from electron- to phonon-dominated relaxation

We study the relaxation of the Holstein model after a sudden switch-on of the interaction by means of the nonequilibrium dynamical mean field theory, with the self-consistent Migdal approximation as an impurity solver. We show that there exists a qualitative change in the thermalization dynamics as the interaction is varied in the weak-coupling regime. On the weaker interaction side of this crossover, the phonon oscillations are damped more rapidly than the electron thermalization time scale, as determined from the relaxation of the electron momentum distribution function. On the stronger interaction side, the relaxation of the electrons becomes faster than the phonon damping. In this regime, despite long-lived phonon oscillations, a thermalized momentum distribution is realized temporarily. The origin of the “thermalization crossover” found here is traced back to different behaviors of the electron and phonon self-energies as a function of the electron-phonon coupling. In addition, the importance of the phonon dynamics is demonstrated by comparing the self-consistent Migdal results with those obtained with a simpler Hartree-Fock impurity solver that neglects the phonon self-energy. The latter scheme does not properly describe the evolution and thermalization of isolated electron-phonon systems

Damping of the collective amplitude mode in superconductors with strong electron-phonon coupling

We study the effect of strong electron-phonon interactions on the damping of the Higgs amplitude mode in superconductors by means of nonequilibrium dynamical mean-field simulations of the Holstein model. In contrast to the BCS dynamics, we find that the damping of the Higgs mode strongly depends on the temperature, becoming faster as the system approaches the transition temperature. The damping at low temperatures is well described by a power law, while near the transition temperature the damping shows exponential-like behavior. We explain this crossover in terms of a temperature- dependent quasiparticle lifetime caused by the strong electron-phonon coupling, which smears the superconducting gap edge and makes the relaxation of the Higgs mode into quasiparticles more efficient at elevated temperatures. We also reveal that the phonon dynamics can soften the Higgs mode, which results in a slower damping