We have measured the mutation rates of G(17) and A(17) repeat sequences in cultured mammalian cells with and without mismatch repair and have compared these rates to those of a (CA)(17) repeat sequence. Plasmids containing microsatellites that disrupt the reading frame of a downstream neomycin-resistance gene were introduced into the cells by transfection and revertants were selected using the neomycin analog G418. Comparison of mutation rates within cell lines showed that the mutation rates of A(17) and (CA)(17) sequences were similar in the mismatch repair proficient cells, but the mutation rate of G(17) was significantly higher than that of either A(17) or (CA)(17). In the mismatch repair deficient cells, the G(17) and (CA)(17) mutation rates were similar and were significantly higher than the A(17) rate. PCR analysis of the mutants showed that 1 bp insertions predominated in both mononucleotide repeats in the mismatch repair proficient cells; in mismatch repair deficient cells, 2 bp deletions were the most common mutation in the A(17) sequence, but 1 bp insertions and 2 bp deletions were equally represented in the G(17) sequence. These results indicate that a G(17) repeat is less stable than an A(17) repeat in both mismatch repair proficient and mismatch repair deficient mammalian cells. This observation implies that the replication fidelity is lower in G(17) repeats.

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The influence of uniaxial compressive stress on small-signal relative permittivity and direct piezoelectric coefficient of polycrystalline Li-modified (K0.5Na0.5)NbO3 (0, 2, and 4 mol. % Li) was characterized as a function of temperature from 25 to 450 °C. These data reveal corresponding anomalies in both the dielectric and piezoelectric properties near the well-known structural phase transitions in (KxNa1 − x)NbO3. In particular, increasing stress was found to shift the orthorhombic–tetragonal (TO−T) and tetragonal–cubic (TC) phase boundaries to higher temperatures, thereby stabilizing the lower symmetry phases. Experimental results also show that stress up to a critical value flattens the piezoelectric response below TO−T, above which a monotonic decrease is observed. In contrast, permittivity is increased below TO−T with increasing stress. These results are used to construct a stress–temperature phase diagram of Li-modified (K0.5Na0.5)NbO3.

The small‐signal direct piezoelectric coefficient and dielectric permittivity are characterized as a function of temperature from 25 to 450 °C and uniaxial compressive stress up to 80 MPa in porous Pb(Zr,Ti)O3 (PZT; 10, 20, 30, 40, and 50 vol% porosity). Results show retention of piezoelectric response throughout the temperature range with increasing porosity up to 30 vol%, above which a subsequent decrease is observed. Similarly, increasing porosity did not result in a significant change of the depolarization temperature, although a slight increase in the Curie point is observed with increasing porosity. Macroscopic experimental results are discussed together with microcomputed tomography, which shows the 3D pore structure. These results are important for sensing applications that operate at elevated temperatures and apply compressive stress to the electroactive element.

The effect of uniaxial compressive stress on the crystal structure of a 6 mol. % Li-doped (K,Na)NbO3 (LKNN6a) ceramic was investigated using in situ synchrotron X-ray diffraction, revealing the stress-induced relative change in monoclinic Pm and tetragonal P4mm phases. As such, stress-induced phase transformations, in addition to the lattice deformation and domain switching, are the contributing factors for the observed macroscopic mechanical behavior of LKNN6a. The in situ stress-dependent diffraction data also demonstrates a method to mechanically modulate the polymorphic phase transition temperature (TPPT) to a higher temperature, as observed by the temperature-dependent permittivity measurements under a constant bias stress. The external uniaxial compressive stress increases the stability of the lower symmetry monoclinic phase, shifting TPPT to a higher temperature by 60 °C for the maximum uniaxial compressive stress of 300 MPa in the studied composition. Importantly, the stress-induced stabilization of the room-temperature ferroelectric phase can be useful to optimize the phase transition region, as well as increase the temperature stability of lead-free KNN.