Subcritical switching dynamics and humidity effects in nanoscale studies of domain growth in ferroelectric thin films

Ferroelectric domain switching in c-axis-oriented epitaxial Pb(Zr$_{0.2}$Ti$_{0.8}$)O$_3$ thin films was studied using biased scanning probe microscopy tips. While linear and logarithmic dependence of domain size on tip bias and writing time, respectively, are well known, we report an additional linear dependence on relative humidity in the 28-65% range. We map out the switched domain size as a function of both the tip bias and the applied pulse time and describe a growth-limited regime for very short pulses and a nucleation-limited regime for very low tip bias. Using "interrupted-switching" measurements, we probe the nucleation regime with subcritical pulses and identify a surprisingly long relaxation time on the order of 100 ms, which we relate to ionic redistribution both on the surface and within the thin film itself.Comment: 11 pages, 4 figure

Understanding polarization vs. charge dynamics effects in ferroelectric-carbon nanotube devices

To optimize the performance of multifunctional carbon nanotube-ferroelectric devices, it is necessary to understand both the polarization and charge dynamics effects on their transconductance. Directly comparing ferroelectric Pb(Zr0.2Ti0.8)O3 and dielectric SrTiO3 field effect transistors, we show that the two effects strongly compete, with transient charge dynamics initially masking up to 40% of the ferroelectric field effect. For applications, it is therefore crucial to maximize the quality of the ferroelectric film and the interface with the carbon nanotube to take full advantage of the switchable polarization.Comment: 5 pages, 4 figure

Efficacy of once- and thrice-daily dosing of aminoglycosides in in-vitro models of infection

The bactericidal efficacy of amikacin, isepamicin and netilmicin was studied against Pseudomonas aeruginosa and Serratia marcescens over a treatment period of 30 h using two one-compartment in-vitro models with differently designed culture compartments. High bacterial inocula were exposed to fluctuating drug concentrations, simulating human serum concentrations (t½ = 2 h) during clinical treatment. The same daily dose was administered as 1 h infusions given every 8 h or every 24 h, resulting in peak concentrations of 8 and 24 mg/l for netilmicin, and 24 and 72 mg/l for amikacin and isepamicin, respectively. Once-daily dosing was more bactericidal during initial treatment in the in-vitro models (P 99·9% reduction of cfu) after 24 h treatment against S. marcescens compared with P. aeruginosa (P < 0·01). All nine regimens providing peaks of at least four times the MIC were bactericidal against S. marcescens after 24 h exposure. In contrast, a bactericidal effect against P. aeruginosa occurred only during two of six experiments with peaks of four to nine times the MIC. Similar results were obtained in both in-vitro models of infection. These data suggest insufficient intrinsic activity of the aminoglycosides studied for single drug treatment of P. aeruginosa in the absence of host-defence mechanism

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Book Review: Women and Entrepreneurship: Female Durability, Persistence and Intuition at Work

Review of Women and Entrepreneurship: Female Durability, Persistence and Intuition at Work by Mirjana Radović-Marković and Beatrice E. Avolio Alecchi; Gower Publishing, Ltd., 2013