Gelatin is a nature-derived protein having good cytocompatibility, and widely used in tissue engineering particularly in a form of a hydrogel. To obtain the hydrogel with good enough mechanical properties, however, measures are still need to be taken. In this work, the gelatin molecule was modified with methacrylic acid (MA) to obtain crosslinkable gelatin (GM), which formed a chemically crosslinked hydrogel by photoinitiating polymerization. The gelation time could be easily tuned and showed an inverse relationship with the GM concentration. After photo-irradiation for 20 min there was no detectable double carbon bond in the hydrogen spectrum of high resolution magic angle spinning nuclear magnetic resonance spectroscopy ((1)H HR-MAS NMR). With the increase of the GM concentration, storage modulus and loss modulus of the hydrogels increased, but their swelling ratio and mesh size decreased. Weight loss of the hydrogels was also affected by the polymer concentration. Transform growth factor-beta1 (TGF-beta1) was incorporated into the GM hydrogel to improve its bioactivity. In vitro chondrocyte culture showed that the GM hydrogel had indeed good performance to support chondrocyte growth and maintain chondrocytic phenotype. Incorporation of TGF-beta1 could further improve the biological activity in terms of cell proliferation and extracellular matrix secretion.

This article uses a case study in Southeast China to demonstrate how the substantial changes in rural livelihoods have been driven by a combination of ''pull'' forces from external economic development, and ''push'' forces from local areas, leading to a shift in rural household economic activities: household outmigration and de-population of the countryside, changes in energy consumption, and most importantly, changes in land uses and eventually, ecological restoration. Such dramatic changes are becoming common across the Chinese countryside. It is pointed out that economic development has generally caused a deterioration of the environment at least at the early period of economic growth, but the positive impacts, especially in some ecosystem in rural areas, have become more apparent.

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