Abstract

Abstract

Abstract

Abstract

In this lecture I first discuss the fundamentals of self-organizedformation of nanoscale dot and ripple patterns due to ion-inducedperturbation of a surface layer which exhibits a certain ion-inducedviscosity. Viscous flow is the smoothing mechanism and ion-inducederosion and subsurface mass transport in the collision cascade is theroughening mechanism.Examples of ripple pattern formation on Si, SiO_2 and a-C surfaces anddifferent incident ions are presented. The experimental observations arethen compared to predictions made by simple theoretical models. Theparameters needed in the theoretical models are obtained from binarycollision Monte Carlo Simulations (SDTRIM) or molecular dynamicssimulation. In this context the crater function concept is exemplified.The important role of metal impurities on pattern formation ishighlighted with several examples. It is shown that silicide or carbideformation is now the driving force for pattern formation. Co-depositionof metal impurities from multiply sources allow the design of dotpatterns with predefined symmetry.Finally I discuss the dynamic behavior of ion induced patterns, inparticular the propagation of ripples across the surface. Recentexperiments on ripple propagation will be compared with theoreticalpredictions with some surprising results.

Abstract

We analyze the dynamics of overlapping antiparallel treadmillingmicrotubules in the presence of crosslinking processive motor proteinsthat counterbalance an external force. We show that coupling the force-dependent velocity of motors and the kinetics of motor exchange with abath in the presence of treadmilling leads generically to oscillatorybehavior. In addition, we show that coupling the polymerization kineticsto the external force through the kinetics of the crosslinking motors canstabilize the oscillatory instability into finite-amplitude nonlinearoscillations and may lead to other scenarios, including bistability. Reference : (2012) EPL 98 68005