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The fatigue performance of the high-strength magnesium alloy AZ 80 is studied in air as well as in aqueous 0.5 and 3.5% NaCl solutions. The effect of mechanical surface treatments, specifically mechanical polishing, shot peening, and roller burnishing on the S-N curves, is investigated using an electropolished surface as a reference. While mechanical polishing as well as shot peening improves fatigue performance in air, no improvement is observed in NaCl solutions. However, roller burnishing, which combines a smooth surface finish with residual compressive stresses in sufficient depths, leads to outstanding fatigue performance even in 3.5% NaCl solution. [ABSTRACT FROM AUTHOR]

DNA mismatch repair systems play an essential role in the maintenance of genetic information in living organisms and are also implicated in genetic recombination and genome stability. Using degenerate primers, we have cloned the first plant homologue of the E. coli MutL gene, which we have called AtMLH1 for Arabidopsis thaliana MutL-homologue 1. AtMLH1 is present as a single-copy gene in the Arabidopsis genome and is located on the top arm of chromosome 4. Sequence analysis revealed that the product of this gene shows extensive sequence homology with other eukaryotic MLH1 proteins. As mlh1-deficient lines would be useful for studying the biological function of this gene, several populations that had been mutagenized using T-DNA and transposon insertions were screened to identify such mutants. One line that carries a T-DNA insertion in the promoter region of the AtMLH1 gene was isolated. Surprisingly, although the insertion occurred only ≈80 bp upstream of the putative transcription start site, Northern analyses revealed very low but similar amounts of AtMLH1 transcript in both the wild type and the T-DNA insertion lines. RT-PCR analyses suggest, however, that transcription is initiated further upstream in the insertion line and that the T-DNA may supply this novel initiation site. Finally, no increase in microsatellite instability – a phenotype often associated with mutations in mismatch repair genes – was observed in plants homozygous for this insertion. [ABSTRACT FROM AUTHOR]

A liquid column with height H, trapped in a capillary tube of radius R, possesses a mechanical eigenfrequency. The axis of the capillary tube is oriented parallel to the gravitational force, so that the lower meniscus is fixed at the lower end of the tube, if the density $ \rho $ of the liquid is higher than that of the surrounding fluid. Basic assumptions of the linear theory are a pinned contact line, the spherical cap approximation and $ H \gg R $ . The shape of the susceptibility function, the dimensionless ratio of the mean liquid displacement to the driving pressure gradient plotted versus frequency, depends on the parameter $ X_0 = \omega_0/\omega_c $ only, where $ \omega_0 $ denotes the eigenfrequency of the undamped system and $ \omega_c = \eta /(\rho R^2) $ stands for the characteristic frequency with the viscosity $ \eta $ . For $ X_0 > \sqrt{24} $ the system is underdamped and resonance occurs, while for $ X_0 < \sqrt{24} $ the system is overdamped and resonance cannot be observed. If one interpretes capillary tubes as a model of a porous medium, the present mechanism contributes to the damping of sound waves in porous media saturated by two immiscible fluids, one of them being trapped. [ABSTRACT FROM AUTHOR]