In this paper, we systematically proposed the strategy of tailoring strain delocalization to evade long-standing strength-ductility trade-off dilemma. The scientific contribution is to define and, ...for the first time, to expand the category of strain localization into the whole deformation process, including elastic lattice distortion, plasticity-relevant statistical behaviors (dislocation, twinning, shear/slip bands, necking, etc.), and crack-dependent damage accumulation. The viewpoint we proposed is that the achieving of strength-ductility synergy depends on the delocalizing of aforementioned localized strains. Using hierarchical materials as an example, the design of heterogeneous structure significantly influences the strain delocalization behaviors in terms of internal stress/strain (elastic stage), local strain evolution (plastic stage), and cracking (fracture stage). Relationships among the heterogeneous microstructure, microscopic stress/strain evolution, macroscopic mechanical properties are established. In particular, we assess their influences on strain delocalization from the perspective of slip transfer, plastic stability, damage micromechanics, and crack propagation. A methodological framework is then suggested to understand the materials behaviors in the future using the rapidly developed physics-based multi-dimensional computational models and advanced in situ strain characterization techniques. Innovations towards excellent strength-ductility synergy and expanding applications are increasingly advocated, through promoting strain delocalization and indentifying the current challenges and future opportunities.
PM2.5 refers to ambient air particulate matter with aerodynamic diameters ≤ 2.5 µm, which has been a global environmental problem threatening public health in recent years. Melatonin serving as one ...of the predominant hormones secreted by the pineal gland displays multiple pharmacological properties in various diseases. However, little is known about the possible effects of melatonin in the development of lung injury induced by PM2.5. This study was designed to explore the potential roles of melatonin as well as its possible mechanisms in PM2.5-induced lung injury. In the present study, mice were intratracheally instilled with PM2.5 dissolved in sterile water to induce lung injury with or without intragastric administration of melatonin. The results showed that melatonin treatment significantly alleviated lung pathological injury and edema, apart from inhibiting inflammatory cell infiltration. Meantime, melatonin also decreased the makers of ferroptosis and lipid peroxidation products in lung tissues challenged with PM2.5. Additionally, melatonin promoted the nuclear translocation and expression of Nrf2 and the protein degradation of Keap1. However, the pulmonary protection and anti-ferroptosis effect of melatonin were counteracted in Nrf2-deficiency mice. In vitro experiments further demonstrated that Nrf2 knockdown could offset anti-ferroptosis effect of melatonin in MLE-12 lung epithelial cells. Taken together, our study disclosed that melatonin could relieve PM2.5-induced lung injury via inhibiting ferroptosis of lung epithelial cells by activating Nrf2. Hence, melatonin may be a promising candidate against lung injury associated with air particulate matter.
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•PM2.5 was associated with lung epithelial cell ferroptosis.•Melatonin treatment could inhibit PM2.5-induced lung injury in a Nrf2-dependent manner.•Nrf2 activation by melatonin contributes to the inhibition of lung epithelial cell ferroptosis.
A brittle/ductile multilayered composite was designed and fabricated by reaction annealing of pure Ti and Al foils, and comprised alternating α-Ti(Al) layer, α+α2 dual-phase layer, and α2-Ti3Al ...layer. Brittle α2-Ti3Al phase is expected to impart high yield strength to the composite, while the ductile α-Ti(Al) phase provides the desired tensile ductility. The role of α+α2 dual-phase layer is to weaken the deformation incompatibility between α-Ti(Al) and α2-Ti3Al layers. As expected, tensile tests show a good strength-ductility combination. The real-time tracking of local strain evolution process during the tensile deformation provides a new perspective in understanding the relationship between the microstructure and mechanical properties, by which we found the strength-ductility synergy originates from the constrained crack propagation behavior and strain non-localization imparted by multilayered structure. During the tensile deformation, the local Ti3Al cracking firstly occurred, and the size of plastic zone at the crack tip was theoretically predicted and experimentally validated. Additionally, a model was proposed to describe the stress/strain transfer path before and after cracking.
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•The deformation behavior of brittle/ductile multilayered composites was studied in situ.•The interface constraint fundamentally changed the deformation behavior of brittle/ductile multilayered composites.•A model was proposed to describe the local stress/stain transfer process during the tensile deformation.•Our work provided a new perspective from local strain evolution to understand the microstructure/properties relationship.
Laminated Ti-Al composite sheets with different layer thickness ratios have been fabricated through hot pressing followed by multi-pass hot rolling at 500°C.The laminated sheets show strong bonding ...with intermetallic interface layers of nanoscale thickness between the layers of Ti and Al. The mechanical properties of the composites with different volume fractions of Al from 10% to 67% show a good combination of strength and ductility. A constraint strain in the hot-rolled laminated structure between the hard and soft phases introduces an elastic-plastic deformation stage, which becomes more pronounced as the volume fraction of Al decreases. Moreover, the thin intermetallic interface layer may also contribute to the strength of the composites, and this effect increases with increasing volume fraction of the interface layer.
Layered Ti-Al metal composite (LMC) was designed and fabricated by hot-rolling and annealing of pure Ti and Al sheets. The as-prepared composite exhibits high tensile ductility, being superior to any ...individual Ti or Al sheets. The stress/strain evolution and fracture behavior of the LMC were analyzed by in-situ observations during the tensile deformation. Three deformation stages of LMC were clearly observed by neutron diffraction: elastic stage, elastic-plastic stage and plastic stage. It is found that stress partitioning at the elastic-plastic deformation stage improves the strain balance of LMC, but leads to an internal stress accumulated at the interface. Additionally, a strain-transfer from Ti to adjacent Al layers relieves the strain localization of Ti layers in LMC, which improves the ductility of Ti. Both stress partitioning and strain localization of Ti layers facilitate the nucleation of cracks at a low macro strain. However, the crack propagation is constrained by layered structure. In terms of the Al layers, the constrained micro-cracks relieve the stress concentration in Al layer and improve the ductility of Al layers, so that cracking indirectly affects the plastic deformation behavior of LMC, then improving its entire ductility. This work provides a new structural strategy towards simultaneously improving strength and ductility to develop high performance LMC by structural design.
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Polypyrrole (PPy) composites incorporating yttrium iron garnet (YIG) particles were prepared by an
in situ
oxidative polymerization method. The effects of YIG particle loading level on the ...radio-frequency (RF) electromagnetic properties of the YIG/PPy composites were systematically investigated. A negative permittivity behaviour combined with metal-like conduction was observed in the PPy composites, which was due to the low-frequency plasmonic state of free electrons in the formed conducting PPy networks. The Drude model was used to give a good description of the dielectric response. After increasing the YIG loading, the plasma frequency, at which the real part of permittivity changed from negative to positive, shifted to a lower frequency, and the magnitude (absolute value) of negative permittivity also became smaller. In addition, the permeability of the composites showed a relaxation-type frequency dispersion, which was attributed to the combined effect of the magnetic resonance of YIG particles and diamagnetic response of PPy conducting networks. This work can pave the way for exploiting the regulation mechanism of negative permittivity, benefiting the practical applications of polymer metamaterials.
Tunable negative permittivity and relaxation-type dispersion for permeability were evidenced in yttrium iron garnet/polypyrrole metacomposites.
An ultra-low-strain deformation microstructure was revealed for the first time non-destructively in the bulk interior of an annealed laminated Ti-Al composite—in the “fully recrystallized” Al ...layer—by a synchrotron-based micro-diffraction technique, namely differential aperture X-ray microscopy (DAXM), through real space mapping with a very high angular resolution (0.01°). This ultra-low-strain deformation microstructure was found to result from the thermal stress, induced during cooling after annealing, due to the different coefficients of thermal expansion for the Ti and Al layers. The annealed sample was further tensile deformed to a strain of 1.66% and followed by in situ DAXM and analyzed by various misorientation mapping methods. The results pointed to the important effects of the initial microstructure and the interface constraint, as well as the grain size and crystal orientation, on the plastic deformation. A gradient in dislocation density from the layer interface to the center was found in the Al layer of the annealed sample, and this gradient increased slightly during tensile deformation. The variation of the dislocation density was further discussed based on the activation and interaction of dislocations in grains of different sizes and orientations during plastic deformation. The findings of this study provided valuable insights in understanding the constraint effect of the laminated metal composite and the design of novel composite materials.
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Recent studies have shown that MDR could be induced by the high stemness of cancer cells. In a previous study, we found bufalin could reverse MDR and inhibit cancer cell stemness in colorectal ...cancer, but the relationship between them was unclear. Here we identified overexpressing CD133 increases levels of Akt/nuclear factor‐κB signaling mediators and MDR1, while increasing cell chemoresistance. Furthermore, bufalin reverses colorectal cancer MDR by regulating cancer cell stemness through the CD133/nuclear factor‐κB/MDR1 pathway in vitro and in vivo. Taken together, our results suggest that bufalin could be developed as a novel 2‐pronged drug that targets CD133 and MDR1 to eradicate MDR cells and could ultimately be combined with conventional chemotherapeutic agents to improve treatment outcomes for patients with colorectal cancer.
Overexpressing CD133 increases levels of Akt/NF‐κB signaling mediators and MDR1. Bufalin reverses colorectal cancer multidrug resistance by regulating cancer cell stemness via the CD133/NF‐κB/MDR1 pathway.
Oxidative damage and epithelial-mesenchymal transition (EMT) are main pathological processes leading to the development of PM2.5-induced lung fibrosis. Epigallocatechin gallate (EG), a natural ...polyphenol extracted from green tea, possesses the ability to combat oxidative stress and inflammation. However, the potential roles of EG in PM2.5-induced lung fibrosis have not been reported yet. In the present study, we investigated whether EG could relieve PM2.5-induced lung injury and fibrosis in vivo and in vitro. To mimic PM2.5-induced lung fibrosis, C57/BL6 mice were intranasally instilled with PM2.5 suspension, and MLE-12 lung epithelial cells were stimulated with PM2.5 (100 μg/mL) in vitro. The results showed that intragastric administration of EG (20 mg/kg/d or 80 mg/kg/d for 8 weeks) significantly prevented lung injury, inflammation, and oxidative stress in PM2.5-induced mice, apart from inhibiting collagen deposition. Additionally, EG treatment also suppressed the activation of AKT/mTOR signaling pathway in lung tissues challenged with PM2.5. In vitro experiments further demonstrated that EG treatment could enhance cell viability in a concentration-dependent manner in PM2.5-treated MLE-12 lung epithelial cells. Also, the overexpression of constitutively active AKT could offset the inhibitory effects of EG on EMT and oxidative stress in PM2.5-treated MLE-12 lung epithelial cells. Finally, AKT overexpression also blocked the inhibitory effect of EG on the phosphorylation of mTOR in PM2.5-treated MLE-12 lung epithelial cells. In conclusion, EG could improve PM2.5-induced lung fibrosis by decreasing oxidative damage and EMT through AKT/mTOR pathway, which might be a potential candidate for the treatment of PM2.5-induced lung fibrosis.
Multimodal imaging-guided therapy holds great potential for precise theranostics of cancer metastasis. However, imaging agents enabling the convergence of complementary modalities with therapeutic ...functions to achieve perfect theranostics have been less exploited. This study reports the construction of a multifunctional nanoagent (FIP-99mTc) that comprises Fe3O4 for magnetic resonance imaging, radioactive 99mTc for single-photon-emission computed tomography, and IR-1061 to serve for the second near-infrared fluorescence imaging, photoacoustic imaging, and photothermal therapy treatment of cancer metastasis. The nanoagent possessed superior multimodal imaging capability with high sensitivity and resolution attributing to the complement of all the imaging modalities. Moreover, the nanoagent showed ideal photothermal conversion ability to effectively kill tumor cells at low concentration and power laser irradiation. In the in vivo study, FIP-99mTc confirmed the fast accumulation and clear delineation of metastatic lymph nodes within 1 h after administration. Attributing to the efficient uptake and photothermal conversion, FIP-99mTc could raise the temperature of metastatic lymph nodes to 54 °C within 10 min laser irradiation, so as to facilitate tumor cell ablation. More importantly, FIP-99mTc not only played an active role in suppressing cancer growth in metastatic lymph nodes with high efficiency but also could effectively prevent further lung metastasis after resection of the primary tumor. This study proposes a simple but effective theranostic approach toward lymph node metastasis.
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