Activity-dependent CREB phosphorylation: Convergence of a fast, sensitive calmodulin kinase pathway and a slow, less sensitive mitogen-activated protein kinase pathway

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Abstract
Strain engineering has emerged as a powerful tool to enhance the performance of known functional materials. Here we demonstrate a general and practical method to obtain super-tetragonality and giant polarization using interphase strain. We use this method to create an out-of-plane–to–in-plane lattice parameter ratio of 1.238 in epitaxial composite thin films of tetragonal lead titanate (PbTiO3), compared to 1.065 in bulk. These thin films with super-tetragonal structure possess a giant remanent polarization, 236.3 microcoulombs per square centimeter, which is almost twice the value of known ferroelectrics. The super-tetragonal phase is stable up to 725°C, compared to the bulk transition temperature of 490°C. The interphase-strain approach could enhance the physical properties of other functional materials. An epitaxial route to strain Strain can have a dramatic effect on the properties of materials. Zhang et al. introduced a large strain in the material PbTiO3 by growing it epitaxially in a composite with PbO. On the boundaries between the two materials, their normally different lattice constants were matched, giving rise to the strain. As a consequence, the films exhibited a very large electric polarization even in the absence of an electric field. The method may be applicable to generating other functional materials. Scence, this issue p. 494