Pinning of grain boundary migration by a coherent particle

We studied single-particle pinning of grain boundary (GB) migration during grain growth. A phase-field model was formulated to simulate the pinning by a coherent particle and validated quantitatively by comparison with analytical prediction. A study of GB migration velocity using this model revealed that second-phase coherent particles have a previously unknown restraining effect over the whole of the GB-particle interaction range, which is qualitatively different from the interaction between GB and incoherent particles.     

Kinetic pinning versus capillary pinning of voids at the moving interface during reactive diffusion

Two mechanisms of the Kirkendall voids pinning at the moving interface are discussed. Besides common Zener pinning, voids can be additionally, kinetically pinned to the interface by the additional vacancy concentration gradient, existing due to unideal vacancy sinks/sources at the interface and at the both sides of it. Kinetic pinning may explain the influence of copper substrate defect prehistory on the pinning behaviour. Capillary pinning is difficult to apply for the cases of voids enveloping by the growing phase.     

Phase-field simulations of the interaction between a grain boundary and an evolving second-phase particle

We performed phase-field simulations to analyse the interaction of a migrating grain boundary with an evolving second-phase particle. It is found that depending on the difference between the interfacial energies of the particle–matrix interface for the two grain orientations involved and the driving force for grain boundary movement, particles with a particle size well above the critical limit can dissolve due to passage of the boundary.     

Role reversal changes during the ontogeny of play fighting in male rats: Attack vs. defense

From weaning until sexual maturity, the rates at which young male rats hold each other supine during play fighting appear to become progressively asymmetrical. These changes have been previously thought to reflect an initial lack of dominance and a later development of dominance-subordinance relationships. In this paper it is shown that pairs of male rats exhibit asymmetries in playful attack and playful defense throughout development. The changes, resulting in greater asymmetry of pinning rates, are shown to result from age-dependent changes in defensive tactics; the relationship, therefore, remains constant while the form of the behavior changes. Furthermore, it is not the animals showing the highest rates of playful attack who become dominant in older ages.     

Juvenilized play fighting in subordinate male rats

As pairs of male juvenile sibling rats that are housed together become sexually mature, they develop a dominance-subordinance relationship. These dominance relationships appear to be reflected in the play fighting of the pairmates both as juveniles and as young adults, in that the seemingly subordinate partner initiates more playful attacks at both ages. However, as adults, even though it is the subordinate that initiates more playful attacks, it is the subordinate that is pinned on his back by the partner most often. Dominant pairmates were found to switch to defensive patterns typically found in adult males. In contrast, the subordinates, when contacted on the nape, were more likely to retain the juvenile pattern of turning over to supine. Therefore, the subordinate pairmate of an adult pair of male siblings both initiates more playful attacks and defends itself in a more juvenile manner than its dominant partner, and this leads to it being pinned more frequently. This pattern of behavior by subordinate rats is suggested to function as a friendship maintenance mechanism permitting co-existence in multimale colonies.