ABSTRACT
The microstructure of the as-cast AlCoCrFeNi high entropy alloy has been investigated by transmission electron microscopy and atom probe tomography. The alloy shows a very pronounced microstructure with clearly distinguishable dendrites and interdendrites. In both regions a separation into an Al-Ni rich matrix and Cr-Fe-rich precipitates can be observed. Moreover, fluctuations of single elements within the Cr-Fe rich phase have been singled out by three dimensional atom probe measurements. The results of investigations are discussed in terms of spinodal decomposition of the alloying elements inside the Cr-Fe-rich precipitates.
ABSTRACT
DNA methylation plays an important role in the gene-silencing network of higher eukaryotes. We have analyzed the 21.5-kb maintenance methyltransferase (M-MTase) gene, met1, of the multicellular green alga Volvox carteri. The met1 transcript was detected only during the period when DNA replication and cell division are taking place. It encodes a 238 kDa protein containing eight C-terminal activity domains typical of M-MTases, plus upstream DNA-binding domains including the ProDom domain PD003757, which experimental analyses in animal systems have indicated is required for targeting the enzyme to DNA-replication foci. Several insertions of unknown function make Volvox Met1 the largest known member of the Met1/Dnmt1 family. Here we also show that several endogenous transposon families are CpG-methylated in Volvox, which we think causes them to be inactive. This view is supported by the observation that an in vitro CpG-methylated gene introduced into Volvox was maintained in the methylated and silent state over >100 generations. Thus, we believe that Met1 recognizes and perpetuates the in vitro methylation signal, and that the silencing machinery is then able to transduce such a methylation-only signal into a stable heterochromatic (and silent) state.
