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The ferroelastic twin-domain structures and piezoelectric properties were investigated in epitaxial Pb(Zr0.35,Ti0.65)O3 thin films with various c-domain volume fractions by metal organic chemical vapor deposition on (100)cSrRuO3/(100)SrTiO3 substrates. The domain structures could be characterized into three regions: a-domain dominant, c-domain dominant, and their mixed domain regions. The mixed domain structure is quite unusual but formed a bilayer with two regions of different a/c domain proportions: the bottom layer is the a1-a2 domain structure and top layer is the a-c domain structure. The films of the mixed region have attained largest piezoelectric coefficients, d33, presumably due to enhanced a-to-c domain switching. [ABSTRACT FROM AUTHOR]

In order to test a critical lateral dimension in two-dimensional (2D) planar ferroelectrics, epitaxial PbTiO3 thin films are patterned into discrete islands lithographically with different lateral sizes. As the pattern size decreases, the substrate clamping effect is significantly reduced and thus the misfit strain in the films could he relaxed further. Evolution of 90° domain structures as a function of lateral dimensions was characterized extensively by reciprocal space mapping using synchrotron x ray. As the lateral 2D planar size decreases in the PbTiO3 patterns on MgO(001), some of the a domains turned into c domains due to the relaxed tensile strain. In the PbTiO3 patterns on Pt(001 ) /MgO(001), on the other hand, the formation of 90° domains is enhanced by the reduction in compressive misfit strain. Equilibrium domain structures in the PbTiO3 thin film islands are also analyzed by the finite element simulation and found to be consistent with the experimental observation. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated the feasibility of producing fatty-acid-derived hydrocarbons in Escherichia coli. However, product titers and yields remain low. In this work, we demonstrate new methods for improving fatty acid production by modifying central carbon metabolism and storing fatty acids in triacylglycerol. Based on suggestions from a computational model, we deleted seven genes involved in aerobic respiration, mixed-acid fermentation, and glyoxylate bypass (in the order of cyoA, nuoA, ndh, adhE, dld, pta, and iclR) to modify the central carbon metabolic/regulatory networks. These gene deletions led to increased total fatty acids, which were the highest in the mutants containing five or six gene knockouts. Additionally, when two key enzymes in the fatty acid biosynthesis pathway were over-expressed, we observed further increase in strain △cyoA△adhE△nuoA△ndh△pta△dld, leading to 202 mg/g dry cell weight of total fatty acids, ~250% of that in the wild-type strain. Meanwhile, we successfully introduced a triacylglycerol biosynthesis pathway into E. coli through heterologous expression of wax ester synthase/acyl-coenzyme:diacylglycerol acyltransferase (WS/DGAT) enzymes. The added pathway improved both the amount and fuel quality of the fatty acids. These new metabolic engineering strategies are providing promising directions for future investigation. [ABSTRACT FROM AUTHOR]