The controlling deformation mechanisms and grain boundary sliding behavior during low-, medium-, and high-temperature superplasticity (LTSP, MTSP, and HTSP) in fine-grained 5083 Al-Mg base alloys are systematically examined as a function of strain. Grain boundary sliding was observed to proceed at temperatures as low as 200 ЊC. With increasing LTSP straining from the initial ( Ͻ 0.5) to later stages ( Ͼ 1.0), the strain rate sensitivity m, plastic anisotropy factor R, high-angle grain boundary fraction, grain size exponent p, and grain boundary sliding contribution all increased. During the initial LTSP stage, there was little grain size dependence and the primary deformation mechanisms were solute drag creep plus minor power-law creep. At later stages, grain size dependence increased and grain boundary sliding gradually controlled the deformation. During MTSP and HTSP, solute drag creep and grain boundary sliding were the dominant deformation mechanisms.

Low-temperature superplasticity (LTSP) at 250 ЊC and 1 ϫ 10 Ϫ3 s Ϫ1 was observed in a 5083 Al-Mg base alloy after thermomechanical treatments (TMTs). With a higher TMT rolling strain, the fraction of high-angle grain boundaries increased, which was favorable for the further operation of grainboundary sliding (GBS) and LTSP. The near-brass {110}͗112͘, S {123}͗634͘, and Cu {112}͗111͘ texture components in the as-thermomechanically treated specimens gradually evolved into a random orientation distribution during LTSP straining from 30 to 100 pct. Static annealing at 250 ЊC itself could not alter the existing texture. The grain-misorientation distribution curves also showed that, after 100 pct LTSP elongation, the misorientation angles approached the random distribution. In the latter case, the low-, medium-, and high-angle boundaries each would partition around 10, 20, and 70 pct, respectively. When the LTSP elongation was greater than 150 pct, the macrodeformation anisotropy (R) ratio would reach a plateau value of ϳ0.8. During the initial stage, a group of over 60 grains proceeded cooperative grain-boundary sliding (CGBS); most individual grain boundaries started to slide at the later stage. It seems that it is the high-angle boundaries, not the special coincidence-site lattice (CSL) boundaries, which could govern the LTSP performance.

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Mana-Hox, an analog of beta-carbolines with anticancer activity, induces aberrant mitosis and delays mitotic exit. However, the cellular target is not known. In this study, we visualized the intracellular localization of Mana-Hox. Mana-Hox rapidly penetrated into cells (within 1 min) and concentrated on disorganized metaphase chromosomes after 13 hr of exposure. We demonstrated that Mana-Hox is a noncovalent DNA binder that can interact with DNA through intercalation and/or through minor groove binding. Furthermore, Mana-Hox also inhibits topoisomerase II relaxation activity in vitro, suggesting that Mana-Hox could perturb mitotic chromosome decatenation. Overall, Mana-Hox binding to DNA plays a critical role in the induction of aberrant mitosis and contributes to its anticancer activity.

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