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High temperature intergranular crack tip oxidation under a single 600 s long sustained tensile load at 700 °C was studied for the Ni-base superalloy Allvac 718Plus. High-resolution analytical techniques showed oxidation to take place at and immediately ahead of the tip of an open crack, forming a closed but layered oxide structure about the prior (now oxidized) grain boundary. Near the prior grain boundary the oxide is Ni-rich with a Co-enriched layer furthest away from the metal and a Feenriched region below this. A Cr-rich oxide is present below the outer Ni-rich oxides throughout the crack, also in the direction of crack growth. This is believed to have a hindering effect on oxidation ahead of the crack. Ni 3 (Nb,Al) γ' precipitates close to the grain boundaries were found to oxidize and form regions of near-stoichiometric NiO within the oxide layers. Remaining constituents of γ' (e.g. Al and Nb) were found to be enriched in the surrounding oxidized matrix and also to produce thin oxide layers near the interface between unoxidized metal and the Cr-rich oxide. The formation of the crack tip oxides is discussed with regard to thermodynamics, kinetics and the influence of applied mechanical load.

a b s t r a c tThe effect of temperature on the NaCl-induced atmospheric corrosion of the Mg-Al alloy AM50 has been investigated in the laboratory. The corroded samples were analyzed gravimetrically and by SEM, EDX, XRD, and FTIR. The atmospheric corrosion of 99.97% Mg was also studied for reference. While the NaCl-induced atmospheric corrosion of AM50 is strongly reduced with decreasing temperature, 99.97% Mg does not exhibit such a trend. The temperature dependence of the atmospheric corrosion of alloy AM50 is attributed to the aluminum content in the alloy. Several crystalline magnesium hydroxy carbonates formed at 4 and 22°C but were absent at À4°C.

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produced by annealing of sputtered thin films. The in situ XPS study focuses on both the core level peaks and Auger peaks. The peak positions, shapes, satellites as well as Auger parameters are compared for different silicides. The factors that influence the Ni core level peak shifts are discussed. The Ni 2p 3/2 peak shape and satellites are correlated with the valence band structure. The effect of argon ion etching on surface composition and chemical states is also investigated.

Eukaryotic initiation factor 2A is a single polypeptide that acts to negatively regulate IRES-mediated translation during normal cellular conditions. We have found that eIF2A (encoded by YGR054w) abundance is reduced at both the mRNA and protein level during 6% ethanol stress (or 37°C heat shock) under conditions that mimic the diauxic shift in the yeast Saccharomyces cerevisiae. Furthermore, eIF2A protein is posttranslationally modified during ethanol stress. Unlike ethanol and heat shock stress, H2O2 and sorbitol treatment induce the loss of eIF2A mRNA, but not protein and without protein modification. To investigate the mechanism of eIF2A function we employed immunoprecipitation-mass spectrometry and identified an interaction between eIF2A and eEF1A. The interaction between eIF2A and eEF1A increases during ethanol stress, which correlates with an increase in IRES-mediated translation from the URE2 IRES element. These data suggest that eIF2A acts as a switch to regulate IRES-mediated translation, and eEF1A may be an important mediator of translational activation during ethanol stress.

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