In this study, we reviewed the factors affecting the hydrogen embrittlement susceptibility of solution-treated austenitic steels and Ni–Cr (–Fe) alloys with face-centered cubic (FCC) structures. These alloy systems exhibit many microstructural similarities; however, when hydrogen is introduced, they display numerous differences. These differences can be explained in terms of FCC phase stability, dislocation slip planarity, deformation twinnability, and grain boundary strength. Although these factors have been clarified in various studies, they are not comprehensively understood across a wide range of chemical compositions. Recent studies have measured numerous hydrogen embrittlement data in FCC alloys and characterized the elemental effects on relevant metallurgical data, such as phase stability, grain boundary strength, stacking fault energy, and atomistic interactions. Therefore, we summarized and correlated the data to establish a comprehensive alloy design strategy for hydrogen-resistant steels and Ni alloys. Furthermore, the effect of grain refinement and related insights are also discussed toward developing high-strength hydrogen-resistant FCC alloys.

A plastic crystal (PC) has a crystalline phase characterized by disordered molecular (or ionic) orientations while maintaining a regular lattice of their positions. It is in a molten state from the perspective of orientation, while in a crystalline state from the perspective of position. Recent studies have reported heterogeneous dynamics within the PC phase, regardless of whether it is a molecular PC (MPC) or an ionic PC (IPC). By measuring the spin-lattice relaxation time (T₁) and the spin-spin relaxation time (T₂) using low-frequency NMR, it is possible to separately observe the reorientation motion of molecules (or ions) from T₁ and their translational motion from T₂. We present the results of relaxation time measurements using an MPC and an IPC samples. The heterogeneous dynamics is attributed to the existence of static heterogeneous regions in the PC phase: the core region and the surrounding region enveloping it. We demonstrate that molecules (or ions) within each region exhibit distinct translational motion behaviors, with the surrounding region particularly leading to a pre-melting phenomenon. This heterogenization may be described “a phase separation in solid phase”.

Loss-of-function mutations in the evolutionarily conserved protein DJ-1/PARK7 cause autosomal recessive early-onset Parkinson’s disease. Despite being identified more than 20 years ago, the authentic molecular function of DJ-1 remains controversial as diverse biochemical activities attributed to DJ-1 often lack a unified mechanistic explanation. In this review, we outline the hydrolase activities of DJ-1 (i.e., deglycase, protease, and esterase activities) before focusing on its glyoxalase activity, which catalyzes the glutathione-independent detoxification of reactive α-oxoaldehydes such as methylglyoxal. We summarize the historical identification of glyoxalase III activity, the discovery of bacterial and fungal DJ-1 homologs as methylglyoxalases, and the extension of this concept to human DJ-1. Structural and biochemical studies have clarified the molecular mechanism by which DJ-1 hydrolyzes glyoxal and methylglyoxal. In this mechanism, the conserved active-site cysteine residue (Cys106), together with neighboring residues, such as Glu18 and the Gly74-Gly75 oxyanion hole, cooperatively contribute to methylglyoxal degradation. These insights provide a coherent molecular framework that reconciles enzymatic activity with the structural features and evolutionary conservation of the DJ-1 family. Together, they provide a foundation for understanding the biological basis of DJ-1–mediated α-oxoaldehyde detoxification. Lastly, the limitations and unresolved questions of the DJ-1 glyoxalase hypothesis are discussed.