Urban agglomerations have become a new geographical unit in China, breaking the administrative fortresses between cities, which means that the population and economic activities between cities will become more intensive in the future. Constructing and optimizing the ecological security pattern of urban agglomerations is important for promoting harmonious social-economic development and ecological protection. Using the Harbin-Changchun urban agglomeration as a case study, we have identified ecological sources based on the evaluation of ecosystem functions. Based on the resistance surface modified by nighttime light (NTL) data, the potential ecological corridors were identified using the least-cost path method, and key ecological corridors were extracted using the gravity model. By combining 15 ecological sources, 119 corridors, 3 buffer zones, and 77 ecological nodes, the ecological security pattern (ESP) was constructed. The main land-use types composed of ecological sources and corridors are forest land, cultivated land, grassland, and water areas. Some ecological sources are occupied by construction, while unused land has the potential for ecological development. The ecological corridors in the central region are distributed circularly and extend to southeast side in the form of tree branches with the Songhua River as the central axis. Finally, this study proposes an optimizing pattern with “four belts, four zones, one axis, nine corridors, ten clusters and multi-centers” to provide decision makers with spatial strategies with respect to the conflicts between urban development and ecological protection during rapid urbanization.

In view of the poor water solubility and low oral bioavailability of mangiferin (MG), in this study, the supercritical antisolvent (SAS) technology was used to prepare mangiferin microparticles (MG MPs) with N,N-dimethylformamide (DMF) as solvent and carbon dioxide as antisolvent, so as to improve its water solubility, antioxidant capacity and oral bioavailability. Four factors affecting the solubility of the MG MPs were investigated by orthogonal design (OAD), including precipitation pressure, precipitation temperature, MG concentration and feeding speed, and the optimal preparation conditions were determined by range and variance analysis (ANOVA). Under the optimal conditions, the spherical MG MPs with an average diameter of 532.8 nm was obtained, and the yield of the powder was about 95.3%. Scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-Ray Diffractometry (XRD), differential scanning calorimetry (DSC), and thermal gravimetric (TG) were used to analyze the characteristics of the MG MPs. The results obtained showed that the chemical structure of the MG did not change before and after supercritical crystallization, but its particle size and crystallinity decreased significantly. The MG MPs had a higher solubility, and was about 4.26, 2.1 and 2.5 times than that of free MG in water, artificial gastric juice (AGJ) and artificial intestinal juice (AIJ), respectively. The dissolution rate of the MG MPs were also obviously higher than that of free MG. Furthermore, the bioavailability of the MG MPs in vivo was about 2.07 times higher than that of the free MG, and its antioxidant capacity was also much higher than that of free MG, which was close to vitamin C.