http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
( Xiaoning Li ),( Si-xiang Ling ),( Chun-wei Sun ),( Bao-long Zhu ),( Ming-uuan Sun ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2
This work addresses the freeze-thaw cycles of subgrade in seasonal permafrost region western Sichuan plateau. The mechanism of freeze-thaw cycle effect of seasonal frozen subgrade under freeze-thaw cycle is explained. The analysis results show that the variation tendency of the simulated results are in good agreement with that of the field measured results. The freezing depth of the slope foot is smaller than that of the natural ground and is larger than that of the roadbed, which is affected by the freeze-thaw cycle effect, the freezing depth of the roadbed is more easily and the freezing depth is further increased. During the freezing period, a freezing front quickly forms at the natural ground surface with the water below migrates to it. The variation of the saturation at the maximum freezing depth is affected not only by the ambient temperature of the surface boundary during the melting period, but also by the continuous downward flow of cold energy, which makes the ambient temperature down to the freezing temperature, resulting in a short period of freezing, and in consequence, the saturation decreases briefly. Under the same circumstances, the closer the freezing front is to the underground water level, the smaller the frost heave and thawing settlement rate are. The water-thermal coupling effect has a further affect on the frost heaving rate.
Biochemical Properties and Physiological Roles of NADP-Dependent Malic Enzyme in Escherichia coli
Baojuan Wang,Peng Wang,Enxia Zheng,Xiangxian Chen,Hanjun Zhao,Ping Song,Ruirui Su,Xiaoning Li,Guoping Zhu 한국미생물학회 2011 The journal of microbiology Vol.49 No.5
Malic enzymes catalyze the reversible oxidative decarboxylation of L-malate using NAD(P)^+ as a cofactor. NADP-dependent malic enzyme (MaeB) from Escherichia coli MG1655 was expressed and purified as a fusion protein. The molecular weight of MaeB was about 83 kDa, as determined by SDS-PAGE. The recombinant MaeB showed a maximum activity at pH 7.8 and 46°C. MaeB activity was dependent on the presence of Mn^(2+) but was strongly inhibited by Zn^(2+). In order to understand the physiological roles, recombinant E. coli strains (icdNADP/ΔmaeB and icdNAD/ΔmaeB) containing NADP-dependent isocitrate dehydrogenase (IDH), or engineered NAD-dependent IDH with the deletion of the maeB gene, were constructed using homologous recombination. During growth on acetate, icd^(NAD)/ΔmaeB grew poorly, having a growth rate only 60% that of the wild-type strain (icd^(NADP)). Furthermore, icd^(NAD)P/ΔmaeB exhibited a 2-fold greater adaptability to acetate than icdNAD/ΔmaeB, which may be explained by more NADPH production for biosynthesis in icd^(NAD)P/ΔmaeB due to its NADP-dependent IDH. These results indicated that MaeB was important for NADPH production for bacterial growth on acetate. We also observed that MaeB activity was significantly enhanced (7.83-fold) in icd^(NAD), which was about 3-fold higher than that in icd^(NADP), when switching from glucose to acetate. The marked increase of MaeB activity was probably induced by the shortage of NADPH in icd^(NAD). Evidently, MaeB contributed to the NADPH generation needed for bacterial growth on two carbon compounds.