Osteochondral regeneration remains a key challenge because of the limited self-healing ability of the bone and its complex structure and composition. Biomaterials based on endochondral ossification (ECO) are considered an attractive candidate to promote bone repair because they can effectively address the difficulties in establishing vascularization and poor bone regeneration via intramembranous ossification (IMO). However, its clinical application is limited by the complex cellular behavior of ECO and the long time required for induction of the cell cycle. Herein, functionalized microscaffold–hydrogel composites are developed to accelerate the developmental bone growth process via recapitulating ECO. The design comprises arginine–glycine–aspartic acid (RGD)-peptide-modified microscaffolds loaded with kartogenin (KGN) and wrapped with a layer of RGD- and QK-peptide-comodified alginate hydrogel. These microscaffolds enhance the proliferation and aggregation behavior of the human bone marrow mesenchymal stem cells (hBMSCs); the controlled release of kartogenin induces the differentiation of hBMSCs into chondrocytes; and the hydrogel grafted with RGD and QK peptide facilitates chondrocyte hypertrophy, which creates a vascularized niche for osteogenesis and finally accelerates osteochondral repair in vivo. The findings provide an efficient bioengineering approach by sequentially modulating cellular ECO behavior for osteochondral defect repair.
AC electric air arcs in medium voltage (MV) distribution networks, including railway catenary, photovoltaic power generation systems, and traditional distribution networks, can cause insulation damage accidents. Although various studies have been performed on the macroscopic characteristics of the MV AC arc in the air, the research on the physical properties of the arc, such as temperature field and particle composition, is relatively lacking. This work deals with diagnosing the temperature and particle composition of the arc under laboratory conditions based on the arc generation and the moiré deflection diagnosis systems. Based on the experimental results, there are three typical stages in developing the MV AC arc: the initial, transition, and stable combustion. The temperature during the stable combustion of the arc is between 1500–2100 K, while the fluctuation period is half a power frequency cycle. The particle components of the arc are mainly composed of O2, N2, and O. Different from the DC arc, the AC arc exhibits a zero-crossing extinguishing phenomenon, while the gap temperature is still high after extinguishing the arc, and the insulation has not been fully restored. This research provides a method for diagnosing MV AC arcs in the air under laboratory conditions and initial values for the arc modeling.
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