[Research advances in critical transition and its ecological mechanisms of terrestrial ecosystems.].

With the exacerbating disturbances of climate changes and human activities to terrestrial ecosystems, more and more studies realize that ecosystems are at the risk of shifts without warning in structural and functional states and recovery from perturbations require more time. Developing an early warning model to identify critical transition and understanding its ecological mechanism of typical ecosystems have become hotspot in ecological researches. At present, based on theoretical and experimental researches across multiple spatiotemporal scales, a variety of theoretical frameworks and indicators of early warning signals (EWSs) were proposed to signal terrestrial ecosystem critical transition.

Isolation of Flavonoids From Wild Aquilaria sinensis Leaves by an Improved Preparative High-Speed Counter-Current Chromatography Apparatus.

Four flavonoids including apigenin-7,4'-dimethylether, genkwanin, quercetin, and kaempferol were isolated in a preparative or semi-preparative scale from the leaves of wild Aquilaria sinensis using an improved preparative high-speed counter-current chromatography apparatus. The separations were performed with a two-phase solvent system composed of hexane-ethyl acetate, methanol-water at suitable volume ratios. The obtained fractions were analyzed by HPLC, and the identification of each target compound was carried out by ESI-MS and NMR.

[Study on Triterpenoids from Helicteres angustifolia by High-Speed Countercurrent Chromatography].

Objective: To develop a method for separation and purification of triterpenoids from Helicteres angustifolia by highspeed countercurrent chromatography( HSCCC).

Methods: The ethyl acetate extract of Helicteres angustifolia were separated by two-step HSCCC. The structures of the target compounds were identified by ESI-MS and1H-NMR and characterized by FTIR.

The genetic basis of white tigers.

The white tiger, an elusive Bengal tiger (Panthera tigris tigris) variant with white fur and dark stripes, has fascinated humans for centuries ever since its discovery in the jungles of India. Many white tigers in captivity are inbred in order to maintain this autosomal recessive trait and consequently suffer some health problems, leading to the controversial speculation that the white tiger mutation is perhaps a genetic defect. However, the genetic basis of this phenotype remains unknown.

[Separation of eleutheroside E from crude extract of Radix Acanthopanacis Senticosus by analytical and preparative high-speed countercurrent chromatography].

Analytical high-speed countercurrent chromatography (HSCCC) was used for the systematic optimization of the two-phase solvent system to separate eleutheroside E from crude extract of Radix Acanthopanacis Senticosus. Eleutheroside E was obtained by preparative HSCCC with two-phase solvent system composed of chloroform-methanol-isopropanol-water (5:6:1:4 in volume ratio). The mobile phase is the lower phase and operated at a flow-rate of 2.