No abstract

A series of pyrimido[4,5-b]quinoline-2,4-dione derivatives was synthesized and evaluated for their cytotoxic activities in vitro against five human cancer cell lines. Selected compounds were tested for their MDM2 E3 ligase inhibitory activities and p53-MDM2 binding inhibitory activities. Among tested compounds, four sulfur-containing compounds (4-7) displayed enhanced cytotoxic activities and better MDM2 E3 ligase inhibitoty activities in comparison with that of HLI98c. Three compounds (4-6) showed better p53-MDM2 binding inhibitory potency with IC50 values ranging from 1.3 μM to 9.0 μM.

In order to evaluate the influence of freeze–thaw action on the durability of concrete structures, this paper presentedan experimental study to investigate the effects of freezing–thawing cycles and concrete strength on the bond behavior between steel bars and concrete confined with stirrups. Through freeze–thaw cycles and center pullouttests, the failure mode of pullout specimen, concrete strength, mass loss, dynamic elastic modulus, and bond–slip curves were analyzed. At last, the bond–slip constitutive model was proposed for specimens with stirrup confinement under freeze–thaw action. Main test results indicate that the failure mode and shape of bond–slip curves are affected by stirrups. The bond strength hasa certain increase after 100 freeze–thaw cycles owing to the constraining force from stirrups, whereasthe splitting tensile strengthsignificantly declines. After 100 freeze–thaw cycles, the splitting tensile strength of C20 and C40 decreased by40.8% and 46.5%, respectively. The formula was provided to calculate the bond strength of constrained concrete after freeze–thaw cycles, and the damage coefficient and other related parametersin the formula were suggested. The predicted bond–slip curves are close to the experimental results, which could provide reference for the related research of bond performance after freeze–thaw action.