Hillslope Evolution by Bedrock Landslides     

AL Densmore  RS Anderson  BG McAdoo  MA Ellis 《Science (New York, N.Y.)》1997,275(5298):369-372

Bedrock landsliding is a dominant geomorphic process in a number of high-relief landscapes, yet is neglected in landscape evolution models. A physical model of sliding in beans is presented, in which incremental lowering of one wall simulates baselevel fall and generates slides. Frequent small slides produce irregular hillslopes, on which steep toes and head scarps persist until being cleared by infrequent large slides. These steep segments are observed on hillslopes in high-relief landscapes and have been interpreted as evidence for increases in tectonic or climatic process rates. In certain cases, they may instead reflect normal hillslope evolution by landsliding.  相似文献   

Gold nanoelectrodes of varied size: transition to molecule-like charging   总被引：1，自引：0，他引：1  

S Chen  RS Ingram  MJ Hostetler  JJ Pietron  RW Murray  TG Schaaff  JT Khoury  MM Alvarez  RL Whetten 《Science (New York, N.Y.)》1998,280(5372):2098-2101

A transition from metal-like double-layer capacitive charging to redox-like charging was observed in electrochemical ensemble Coulomb staircase experiments on solutions of gold nanoparticles of varied core size. The monodisperse gold nanoparticles are stabilized by short-chain alkanethiolate monolayers and have 8 to 38 kilodaltons core mass (1.1 to 1.9 nanometers in diameter). Larger cores display Coulomb staircase responses consistent with double-layer charging of metal-electrolyte interfaces, whereas smaller core nanoparticles exhibit redox chemical character, including a large central gap. The change in behavior is consistent with new near-infrared spectroscopic data showing an emerging gap between the highest occupied and lowest unoccupied orbitals of 0.4 to 0.9 electron volt.  相似文献