Compositions of aliphatic des-A-triterpenes in the Hani peat deposit,Northeast China and its biological significance

Aliphatic des-A-triterpenes, the degradation products of pentacyclic triterpenes have been tentatively assigned in samples taken from a 963-cm-thick peat sequence from the Hani region of Northeast China using gas chromatography-mass spectrometry (GC-MS) in order to understand and identify these des-A-triterpenes response to climate and ecology. The study indicates that aliphatic des-A-triterpenes are abundant in the Hani peat bog. The high relative abundance of the total des-A-triterpenes mainly occurs at the Holocene periods and is corresponding to the low sedimentation rate. The mechanism of des-A-triterpenes accumulation is not consistent with the previous studies. It is proposed that the biological community is also one influence factor. The obvious stage variations of the total des-A-triterpenes in the whole sequence reveal the different biological (microbes and plants) processes and responses, possibly revealing the four large replacements of biological community and functional composition in the swamp environment over the 16000 cal a BP. The low total des-A-triterpenes values occur at about 10200, 8700, 7700, 6600, 4480–3940 and 3040 cal a BP, reflecting the multiple millennial micro-environment oscillations under the macro-environment of the swamp during the Holocene. The ratios of diene and monoene des-A-triterpenes (DT/MT), des-A-lupane and diene and monoene des-A-triterpenes (DL/(DT+MT)), ratios of individual compounds exhibit vertical opposite to the total des-A-triterpenes. Namely, these ratios are high during the last deglaciation and late Holocene whereas they are low at other periods, indicating different compounds have different responses to micro-environment and microbial activities. This study discusses the diversity of biological community and biological functional composition response to micro-environment, which not only provides the complement in Northeast China, but also bears important fundamental information for the implication to ecological environment in the future.     

用双电层理论研究不同电价阳离子对α半水石膏水化的影响

通过水化升温曲线、ζ电位、液相组成等的测定，研究了不同电价阳离子对α半水石膏水化硬化过程的影响。结果表明：在α半水石膏的水化硬化过程中，形成了双电层结构和负ζ电位，不同电价的阳离子对α半水石膏的表面双电层结构和ζ电位产生不同影响．导致α半水石膏颗粒的分散度和溶解速度不同，从而影响了α半水石膏的水化硬化。这种作用机理有别于传统的胶体体系。