Multiscale Theory of Dislocation Climb.

Dislocation climb is a ubiquitous mechanism playing a major role in the plastic deformation of crystals at high temperature. We propose a multiscale approach to model quantitatively this mechanism at mesoscopic length and time scales. First, we analyze climb at a nanoscopic scale and derive an analytical expression of the climb rate of a jogged dislocation.

Topology-generating interfacial pattern formation during liquid metal dealloying.

Liquid metal dealloying has emerged as a novel technique to produce topologically complex nanoporous and nanocomposite structures with ultra-high interfacial area and other unique properties relevant for diverse material applications. This process is empirically known to require the selective dissolution of one element of a multicomponent solid alloy into a liquid metal to obtain desirable structures. However, how structures form is not known.

Morphological instability of grain boundaries in two-phase coherent solids.

We show both computationally and analytically that grain boundaries that exhibit shear-coupled motion become morphologically unstable in solid alloys that phase separate into coherent domains of distinct chemical compositions. We carry out simulations of continuum models demonstrating that this instability is mediated by long-range elastic interaction between compositional domains and grain boundaries. In addition, we perform a linear stability analysis that predicts the range of unstable wavelengths in good quantitative agreement with simulations.

An observable for vacancy characterization and diffusion in crystals.

To locate the position and characterize the dynamics of a vacancy in a crystal, we propose to represent it as the ground state density of a pseudo-quantum probe particle associated to the Hamiltonian which has, for the potential energy, the field generated by the atoms in the sample. In this description, the coefficient of the kinetic energy term is a tunable parameter controlling the density localization in the regions of the relevant minima of the potential energy field. Based on this description, we derive a set of collective variables that we use in rare event simulations to identify some of the vacancy diffusion paths in a 2D crystal.

Fetal tachycardia: a role for amiodarone as first- or second-line therapy?

Background: Fetal tachycardias result in serious prenatal and postnatal morbidity and mortality. Intrauterine treatment can improve prognosis dramatically and the therapeutic protocol is well defined. Currently, amiodarone is used as third-line therapy and is reserved for refractory cases.