Localized Solid-State Amorphization at Grain Boundaries in a Nanocrystalline Al Solid Solution Subjected to Surface Mechanical Attrition

Using high-resolution electron microscopy, localized solid-state amorphization (SSA) was observed in a nanocrystalline (NC) Al solid solution (weight per cent 4.2 Cu, 0.3 Mn, the rest being Al) subjected to a surface mechanical attrition treatment. It was found that the deformation-induced SSA may occur at the grain boundary (GB) where either the high density dislocations or dislocation complexes are present. It is suggested that lattice instability due to elastic distortion within the dislocation core region plays a significant role in the initiation of the localized SSA at defective sites. Meanwhile, the GB of severely deformed NC grains exhibits a continuously varying atomic structure in such a way that while most of the GB is ordered but reveals corrugated configurations, localized amorphization may occur along the same GB.

Assessing genetic identity of sporophytic offspring of the brown alga Undaria pinnatifida derived from mono-crossing of gametophyte clones by use of amplified fragment length polymorphism and microsatellite markers

The haploid stage of gametophytes of the subtidal brown alga Undaria pinnatifida can be vegetatively propagated under favorable conditions. This unique characteristic makes it possible to establish independent gametophyte cell lines that are zoospore-derived. Sporophytic offspring can be generated through hybridizing the male and female gametophytes, which are derived from different cell lines. Accumulated experiences in this and other species in Laminariales demonstrated the applicability of this novel way to breed desired strains for open-sea cultivation. Sporophytic offspring originated from mono-crossing of male and female gametophyte clones were shown to have similar morphological characteristics under identical ambient conditions. However, there has been no report to relate this similarity on molecular levels. In this report, amplified fragment length polymorphism (AFLP) and microsatellite markers were used to analyze the genetic identity of sporophytic offspring of U. pinnatifida originated from two mono-crossing lines (M1 and M2), two self-breeding lines (S1 and S2) and one wild population (W). Totally 318 AFLP loci were revealed by use of 11 primer sets, of which 4.7%, 0.3%, 17.9%, 16.4% and 36.5% were polymorphic in M1, M2, S1, S2 and W, respectively. The pairwise genetic identity among the individuals of the same line was assessed. It was shown that offspring from mono-crossing lines had a higher degree of identity (95.6-100%) than self-breeding lines (87.7-98.4%) and the wild population (81.5-92.1%). Analysis by use of six microsatellite loci also revealed a higher genetic identity among individuals of the mono-crossing line, further confirming the results of AFLP analysis. Results from this investigation support, on molecular levels, the novel way to produce and maintain strains in U. pinnatifida by use of different gametophyte cell lines.