Depolarizing field in temperature-graded ferroelectrics from an atomistic viewpoint
An atomistic approach for computing the depolarizing, or internal, electric field in materials with inhomogeneous polarization is developed. Application of the approach for studying the depolarizing fields in technologically important (Ba0.7Sr0.3)TiO3 ferroelectric alloy with temperature gradients has revealed the intrinsic features of these fields as well as their role in the establishment of polarization gradients. It is found that the depolarizing fields are inhomogeneous and can be tailored to yield both zero and non-vanishing potential drops. Such findings could pave the way to unusual thermoelectric materials, photovoltaics and locally conducting materials, all of which are at the frontier of current research.
Delipidation of liver homogenates, using an organic solvent system which does not denature proteins, increases measurable ferritin by 25-33%, compared to ferritin concentrations by standard heat supernatant assays. When applied to polyacrylamide gradient gels, lipid-associated ferritin does not enter the gel but after delipidation, this ferritin co-migrates with cytosolic ferritin and with purified liver ferritin. The biological significance of the association of ferritin with lipid has yet to be examined.