Computer studies of trajectory focusing effects on the total reflection coefficient

Ion beam focusing effects in the azimuthal angle-dependence of the reflection coefficient near the semichannel direction have been studied by computer simulation.     

Supramolecular ion channels from a transmembrane bischolic acid derivative showing two discrete conductances

Bischolic acid derivative 1 linked by m-xylylene dicarbamate at the 3,3'-position was synthesized and the single ion channel properties were examined. Compound 1 showed two clearly distinct conductances, 9.5 (type A) and 25.3 pS (type B), under 500 mM KCl symmetric salt conditions, whereas various conductances, ranging from 5-20 pS, were observed in the tetramethylether analogue reported previously. Results indicate that the replacement of four methylether groups with hydroxyls at the 7, 7', 12, and 12' positions in the bischolic acid framework influences the stability of aggregated (supramolecular) ion channel structures. Ion permeability ratios (potassium/chloride and potassium/sodium) for each type of channel were also determined.     

A New Preparative Method for Allylic Indium(III) Reagents by Reductive Transmetalation of pi-Allylpalladium(II) with Indium(I) Salts

A reductive transmetalation of the pi-allylpalladium(II) complexes, generated in situ from a catalytic amount of a palladium(0) complex and a variety of allylic substrates, with indium(I) salts proceeded smoothly in various solvents, providing a new route for allylindium(III) reagents.     

Tripodal imidazole containing ligands for copper catalyzed ATRP

Tripodal imidazole containing ligands, bis((2‐pyridyl)methyl)(1‐methylimidazole‐2‐yl)methyl)amine (BPIA) and bis(1‐methylimidazole‐2‐yl)methyl)((2‐pyridyl)methyl)amine (BIPA), were synthesized and used for copper catalyzed atom transfer radical polymerization (ATRP) of n‐butyl acrylate (nBA). The molecular weights of poly(n‐butyl acrylate) (PnBA) catalyzed by CuBr/BPIA and CuBr/BIPA complexes increased linearly with nBA conversions and they were close to theoretical values with low polydispersities. ATRP equilibrium rate constant (K_ATRP) measurements showed that bothCuBr/BPIA and CuBr/BIPA complexes had high K_ATRP values, similar to that of CuBr/tri(2‐pyridylmethyl)amine (TPMA), which is one of the ATRP most active ligands. Activators regenerated by electron transfer (ARGET) ATRP of nBA with CuBr₂/BPIA and CuBr₂/BIPA complexes were also conducted and polymerization reached high nBA conversions, resulting in PnBA with low polydispersities. This suggests that the copper complexes with BPIA and BIPA were sufficiently stable and active to conduct ATRP when catalyst concentration was low. ARGET ATRP to form high molecular weight PnBA with CuBr₂/BPIA and CuBr₂/BIPA complexes was also successful. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2015–2024, 2008     

面向单晶SiC原子级表面制造的等离子体辅助抛光技术

目前Si基半导体由于其自身材料特性的限制,已经越来越难以满足高速发展的现代电力电子技术对半导体器件的性能要求.SiC作为新一代半导体材料具有显著的性能优势,但由于其属于典型的难加工材料,实现SiC晶圆的高质量与高效率加工成为了推动其产业化应用进程的关键.本综述在回顾近年来SiC超精密加工技术研究进展的基础上,重点介绍了一种基于等离子体氧化改性的SiC高效超精密抛光技术,分析了该技术的材料去除机理、典型装置、改性过程及抛光效果.分析结果表明,该技术具有较高的去除效率,能够获得原子级平坦表面,并且不会产生亚表面损伤.同时针对表面改性辅助抛光技术加工SiC表面过程中出现的台阶现象,探讨了该台阶结构的产生机理及调控策略.最后对等离子体辅助抛光技术的发展与挑战进行了展望.     

A characteristic ribbon-like supramolecular structure and intermolecular D–A interactions in the crystals of triptycenequinones, triptycene-TCNQs and their clathrates as studied by X-ray investigations

A common ribbon-like structure was found in the crystals of triptycenequinones (TPQs), triptycene-TCNQs (TP-TCNQs) and their clathrates. The characteristic structure can be regarded as a supramolecular unit the formation of which is aided by weak intermolecular D–A interactions. This view is supported by the host–guest D–A interactions appeared in the crystals of the clathrates of 5,8-dimethyl-TPQ and 5,8-dimethoxy-TP-TCNQ. Intermolecular C–HO hydrogen bonds seem to be present in TPQ derivatives.