Abstract.A GIS-based method for the assessment of landslide susceptibility in a selected area of Qingchuan County in China is proposed by using the back-propagation Artificial Neural Network model (ANN). Landslide inventory was derived from field investigation and aerial photo interpretation. 473 landslides occurred before the Wenchuan earthquake (which were thought as rainfall-induced landslides (RIL) in this study), and 885 earthquake-induced landslides (EIL) were recorded into the landslide inventory map. To understand the different impacts of rainfall and earthquake on landslide occurrence, we first compared the variations between landslide spatial distribution and conditioning factors. Then, we compared the weight variation of each conditioning factor derived by adjusting ANN structure and factors combination respectively. Last, the weight of each factor derived from the best prediction model was applied to the entire study area to produce landslide susceptibility maps.Results show that slope gradient has the highest weight for landslide susceptibility mapping for both RIL and EIL. The RIL model built with four different factors (slope gradient, elevation, slope height and distance to the stream) shows the best success rate of 93 %; the EIL model built with five different factors (slope gradient, elevation, slope height, distance to the stream and distance to the fault) has the best success rate of 98 %. Furthermore, the EIL data was used to verify the RIL model and the success rate is 92 %; the RIL data was used to verify the EIL model and the success rate is 53 %.

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Lewis Acid Catalysis in the Oxidative Cycloaddition of Thiophenes.-Thiophenes (I) undergo cycloaddition with various dienophiles, when they are oxidized in situ by MCPBA in the presence of BF 3 ·Et 2 O as Lewis acid. The reactions can be performed in a one-pot reaction or a two-step synthesis. In the two-step sequence S-monoxides are formed primarily by oxidation of thiophenes with MCPBA and then react with dienophiles under neutral conditions in a second step. This prevents the decomposition of acid-labile dienophiles. In all cases endo-products with the bridge S=O group directed to the approaching dienophile are obtained. In either way, the use of BF 3 ·Et 2 O enhances the yields of cycloadducts and the variety of dienophiles that can react with thiophenes than in the case of noncatalyzed reactions. Without added dienophiles either dimers like (XII)-(XV) or S-monoxides like (X) are isolated.-(LI, Y.; THIEMANN, T.; SAWADA, T.; MATAKA, S.; TASHIRO, M.; J. Org. Chem. 62 (1997) 23, 7926-7936; Inst. Adv. Mater. Stud., Kyushu Univ., Kasuga, Fukuoka 816, Japan; EN)

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Electrolysed-reduced water (ERW) contained Platinum nanocolloids (PtNCs) of 1-10 nm, suggesting that PtNCs in ERW functioned as active hydrogen donors and scavenge intracellular reactive oxygen species (ROS). Electron paramagnetic resonance (EPR) analysis revealed that synthesized PtNCs of about 2 nm scavenged superoxide anion radicals and DPPH radicals. Synthesized PtNCs scavenged intracellular ROS and suppressed the growth of human leukemia K562 cells.