Nanoindentation Test of Ion-Irradiated Materials: Issues, Modeling and Challenges.

Exposure of metals to neutron irradiation results in an increase in the yield strength and a significant loss of ductility. Irradiation hardening is also closely related to the fracture toughness temperature shift or the ductile-to-brittle transition temperature (DBTT) shift in alloys with a body-centered cubic (bcc) crystal structure. Ion irradiation is an indispensable tool in the study of the radiation effects of materials for nuclear energy systems. Due to the shallow damage depth in ion-irradiated materials, the nanoindentation test is the most commonly used method for characterizing the changes in mechanical properties after ion irradiation. Issues that affect the analysis of irradiation hardening may arise due to changes in the surface morphology and mechanical properties, as well as the inherent complexities in nanoscale indentation. These issues, including changes in surface roughness, carbon contamination, the pile-up effect, and the indentation size effect, with corresponding measures, were reviewed. Modeling using the crystal plasticity finite element method of the nanoindentation of ion-irradiated materials was also reviewed. The challenges in extending the nanoindentation test to high temperatures and to multiscale simulation were addressed.

The complete chloroplast genome of Actinidia macrosperma.

Actinidia macrosperma (A. macrosperma) is a medicinal plant in China, which has been well known for its activities against leprosy and cancers. In this study, we assembled and characterized the complete chloroplast (cp) genome sequence of A. macrosperma in an effort to provide genomic resources for promoting its conservation. The cp genome is 156,231 bp in length, containing a pair of 23,720 bp inverted repeat (IR) regions, which is separated by a large single copy region (LSC) of 88,214 bp and a small single copy region (SSC) of 20,577 bp. A total of 132 genes were annotated in this cp genome, including 85 protein-coding genes, 39 tRNA genes, and 8 rRNA genes. Phylogenetic analysis highly supported that A. macrosperma was evolutionarily close to another Actinidia species Actinidia deliciosa.