Synthesis, structure, chemical stability, and electrical properties of Nb-, Zr-, and Nb-codoped BaCeO3 perovskites.

We report the effect of donor-doped perovskite-type BaCeO(3) on the chemical stability in CO(2) and boiling H(2)O and electrical transport properties in various gas atmospheres that include ambient air, N(2), H(2), and wet and dry H(2). Formation of perovskite-like BaCe(1-x)Nb(x)O(3±δ) and BaCe(0.9-x)Zr(x)Nb(0.

Error analysis of molecular dynamics and fractal time approximants from a combinatorial perspective.

Trotter's theorem forms the theoretical basis of most modern molecular dynamics. In essence this theorem states that a time displacement operator (a Lie operator) constructed by exponentiating a sum of noncommuting operators can be approximated by a product of single operators provided the time interval is "very small." In theory "very small" implies infinitesimally small (at which point the approximate product becomes exact), while in practical analysis a finite time interval is divided into several small subintervals or steps.

Liquid DEP actuation and precision dispensing of variable volume droplets.

Droplet based microfluidic systems, in recent years, have demonstrated numerous advantages and exciting potential for Lab-On-a Chip applications. In order to fully realize the potential benefits of this technology, one requires precision dispensing and manipulation of droplets of known volume and sample concentration, in a rapid and controlled manner. In this article, we demonstrate the rapid and controlled microactuation of aqueous samples and subsequent dispensing of variable volume droplets in nanolitre to picolitre regime by using a coplanar tapered electrode structure that leverages the phenomena of liquid dielectrophoresis (L-DEP).

Comparison of molecular dynamics and moment based methods as tools in the computation of time dependent correlation functions.

Methods, such as the continued fractions that are based on the exact moments (Taylor coefficients) provide powerful analytic techniques for calculating approximate dynamic correlation functions of physical properties. Owing to the practical difficulties associated with obtaining higher order exact moments these methods have been largely eclipsed by molecular dynamics. In this paper we develop the formalism for extracting trajectory moments from a molecular dynamics trajectory and compare the performance of the two methods.

Correct virial formulation in the isotropic periodic sum method.

The original formulation of the virial in the isotropic periodic sum (IPS) method assumes that the sphere defining the local region has a constant radius (the cutoff) independent of the system size. This assumption neglects a virial term originating from the separation between the local sphere and its periodic images. When comparing the IPS virial with that calculated from the cutoff plus long range correction method, the difference observed can be erroneously attributed to the representation of the infinite region.

Molecular modeling of proton transport in the short-side-chain perfluorosulfonic acid ionomer.

An explanation for the superior proton conductivity of low equivalent weight (EW) short-side-chain (SSC) perfluorosulfonic acid membranes is pursued through the determination of hydrated morphology and hydronium ion diffusion coefficients using classical molecular dynamics (MD) simulations. A unique force field set for the SSC ionomer was derived from torsion profiles determined from ab initio electronic structure calculations of an oligomeric fragment consisting of two side chains. MD simulations were performed on a system consisting of a single macromolecule of the polymer (EW of 580) with the general formula F3C-[CF(OCF2CF2SO3H)-(CF2)7]40-CF3 at hydration levels corresponding to 3, 6, and 13 water molecules per sulfonic acid group.

Effects of dielectric saturation and ionic screening on the proton self-diffusion coefficients in perfluorosulfonic acid membranes.

Proton transport in perfluorosulfonic acid (PFSA) membranes is investigated through a statistical mechanical model that includes the effects of the interaction of the tethered sulfonate groups with both the water and solvated protons. We first derive a potential that describes the electrostatic field due to the dissociated sulfonic acid groups by extending the work of Gronbech-Jensen et al. [ Mol.

Electrorotation of axolotl embryos.

The frequency dependent dielectric properties of individual axolotl embryos (Ambystoma mexicanum) were investigated experimentally utilizing the technique of electrorotation. Individual axolotl embryos, immersed in low conductivity media, were subjected to a known frequency and fixed amplitude rotating AC electric field and the ensuing rotational motion of the embryo was monitored using a conventional optical microscope. None of the embryos in the pregastrulation or neurulation stages of development exhibited any rotational motion over the field frequency range (10 Hz-5 MHz).

Theoretical Model of Electrode Polarization and AC Electroosmotic Fluid Flow in Planar Electrode Arrays.

Strong frequency-dependent fluid flow has been observed near the surface of microelectrode arrays. Modeling this phenomenon has proven to be difficult, with existing theories unable to account for the qualitative trend observed in the frequency spectra of this flow. Using recent electrode polarization results, a more comprehensive model of the double layer on the electrode surface is used to obtain good theoretical agreement with experimental data.