The catalytic activity of PtnCum (n = 1-3, m = 0-2) clusters for methanol dehydrogenation to CO.

A large number of experiments show that PtCu catalyst has a good catalytic effect on methanol decomposition. Therefore, density functional theory (DFT) was used to further study the dehydrogenation of methanol catalyzed by PtnCum (n = 1-3, m = 0-2). The energy diagrams of O-adsorption path and H-adsorption path were drawn. By calculation, the Pt is the active site of the whole reaction process, and the barrier energy of the rate-determining step is 11.09 kcal mol-1 by Pt2Cu, which is lower than that of Pt3 and PtCu2. However, the complete dehydrogenation product of methanol, CO, is easier to dissociate from PtCu2 clusters than from Pt3 and Pt2Cu clusters. Therefore, Cu doping can improve the catalytic activity and anti-CO toxicity of Pt to a certain extent.

Improved two-cuff technique for orthotopic liver transplantation in rat.

BACKGROUND: The first orthotopic liver transplantation in rat (ROLT) was reported by Lee in 1973. Kamada innovatively applied cuff technique to ROLT in 1979. However, the operative procedures were highly demanding and the operative mortality was relatively high. The purpose of this study was to improve the model of ROLT, simplify operative procedures, and enhance the successful rate of operation. METHODS: Orthotopic liver transplantation was performed in 160 Wistar rats by improved two-cuff technique. The portal vein between donor and recipient was anastomosed with the cuff technique. The same method was used to anastomose the infrahepatic vena cava. The suprahepatic vena cava and the hepatic artery were anastomosed by microvascular suturing and the bile duct was anastomosed end to end by a Teflon catheter. RESULTS: The average time for donor operation, graft preparation and anhepatic phase was 31 minutes, 14 minutes and 13 minutes, respectively. The anastomosis time for the suprahepatic vena cava, portal vein, infrahepatic vena cava, hepatic artery and bile duct was 7 minutes, 2 minutes, 2 minutes, 8 minutes and 1 minute, respectively. The main causes for operative mortality were pneumothorax, anesthesia, air embolism and massive bleeding, and the successful rate of operation was 92.5%. The causes for death after operation were stoma bleeding, infection, biliary obstruction and graft failure. CONCLUSION: The improved two-cuff technique can reduce operative mortality, enhance survival rate, and serve as an ideal method for the establishment of animal model of ROLT.

[Dynamic changes of groundwater level and vegetation in water table fluctuant belt in lower reaches of Heihe River: coupling simulation].

Based on the 2006 investigation data in lower reaches of Heihe River, and by using logarithmic normal distribution model, the models about the vegetation cover of Populus euphratica and Tamarix ramossima and the groundwater level in study area were built, and the potential plant of the study area was simulated. The results showed that in the lower reaches of Heihe River, the optimal groundwater level and mean groundwater level for P. euphratica were 2.6 m and 3.6 m, and those for T. ramossima were 2.0 m and 3.0 m, respectively. The high cover P. euphratica distribution area was mainly concentrated in the near-banks of Donghe River and Xihe River, while higher cover T. ramossima was distributed in most parts of the study area. From the aspect of current groundwater level, T. ramossima should be the adaptive species in the study area. The similarities between the potential and actual spatial distribution of P. euphratica and T. ramossima were 43. 4% and 55. 6% , respectively, and the main reason for the lower similarity was that there existed a gypsum salt pan in soil, which blocked the vertical movement of soil water.