No abstract

Atomic‐level manipulation of catalysts is important for both fundamental studies and practical applications. Here, the central metal atom in an atomically precise Ag25 nanocluster (NC) is replaced with a single Pd, Pt, and Au atom, respectively, and employed as a model system to study the structure–property–activity relationship at the atomic level. While the geometric structures are well‐preserved after doping, the electronic structures of Ag25 NCs are significantly altered. The combination of Ag25 and TiO2 enhances the charge separation at the interface, exhibiting a 10 times higher hydrogen production rate in photocatalytic hydrogen evolution reaction compared to bare TiO2. Further results show that heteroatoms doping has a negative impact on performance, particularly in the cases of Pd and Au doping. Ultraviolet photoelectron spectroscopy measurements and density functional theory calculations suggest that the lower activities are due to an energy mismatch between the levels of doped NCs and TiO2. These findings not only reveal the impact of heteroatoms doping on the electronic properties and photocatalytic activities of NCs, but can also guide the design of heterometallic NCs for photocatalytic applications.

Chikusetsusaponin V (CsV), a saponin from Panax japonicus, has been reported to inhibit inflammatory responses in lipopolysaccharide (LPS)-induced macrophage cells. However, whether CsV could alleviate LPS-induced liver injury in vivo and the potential mechanisms involved remain unclear. In the present study, we investigated the anti-inflammatory effects of CsV on LPS-induced acute liver injury in mice and further explored the potential mechanisms involved. Our results showed that CsV significantly attenuated elevation of alanine transaminase (ALT) and aspartate aminotransferase (AST) levels and improved liver histopathological changes in LPS-induced mice. In addition, CsV decreased serum tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) levels and inhibited mRNA expressions of inducible nitric oxide synthase (iNOS), TNF-α and IL-1β in LPS challenged mice. Furthermore, CsV inhibited nuclear factor kappa B (NF-κB) activation by downregulating phosphorylated NF-κB, IκB-α, ERK, c-Jun N-terminal kinase (JNK) and p38 levels in the liver tissue, which ultimately decreased nucleus NF-κB protein level. In conclusion, our data suggested that CsV could be a promising drug for preventing LPS challenged liver injury since it attenuated LPS-induced inflammatory responses, partly via inhibiting NF-κB and MAPK signaling pathways.

This work focuses on a specific aspect of polymer fracture: the onset of cavitation during deformation. Failure in polymers involves plastic deformation by shear yielding and crazing. The competition between these two mechanisms is thought to govern the ductile versus brittle response of the material. The present molecular dynamics (MD) analysis shows that at a small scale, cavitation results from a transition between a homogeneous to a highly heterogeneous deformation field during loading. We characterize here these two regimes thanks to a scalar non-affine displacement probe, which displays a sharp transition at the onset of cavitation. Close scrutiny of cavitation allows for defining a stress-based cavitation criterion, the validity of which is checked for two temperatures in the glassy state. A mapping between the MD results and the corresponding estimates at the continuum scale indicates that the onset of cavitation at high deformation rates corresponds to a noticeably larger stress level as compared with that at low and intermediate loading rates. Since cavitation precedes failure in glassy polymers, this effect could be responsible for the marked increase in toughness reported experimentally under impact conditions.