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排序方式: 共有103条查询结果,搜索用时 140 毫秒
101.
Novel 10‐{[3‐(6‐hydroxy‐2,2‐dimethyltetrahydrofuro[2,3‐d][1,3]dioxol‐5‐yl)‐4,5‐dihydro‐5‐isoxazolyl]methyl}‐9(10H)‐acridinone derivatives (13–16) were synthesized by 1,3‐dipolar cycloaddition using the carbohydrate derivative as dipole and different 10‐allyl‐9(10H)‐acridinone derivatives (9–12) as dipolarophiles. The new cycloadducts as well as the dipolarophiles precursors were characterized spectroscopically. 相似文献
102.
TEM,XRD and AFM study of poly(<Emphasis Type="Italic">o</Emphasis>-ethoxyaniline) films: new evidence for the formation of conducting islands 总被引:1,自引:0,他引:1
Fabio L. Leite William F. Alves Mirta Mir Yvonne P. Mascarenhas Paulo S. P. Herrmann Luiz H. C. Mattoso Osvaldo N. OliveiraJr. 《Applied Physics A: Materials Science & Processing》2008,93(2):537-542
The existence of conducting islands in polyaniline films has long been proposed in the literature, which would be consistent with conducting mechanisms based on hopping. Obtaining direct evidence of conducting islands, however, is not straightforward. In this paper, conducting islands were visualized in poly(o-ethoxyaniline) (POEA) films prepared at low pH, using Transmission Electron Microscopy (TEM) and atomic force spectroscopy (AFS). The size of the islands varied between 67 and 470 Å for a pH=3.0, with a larger average being obtained with AFS, probably due to the finite size effect of the atomic force microscopy tip. In AFS, the conducting islands were denoted by regions with repulsive forces due to the double-layer forces. On the basis of X-ray diffraction (XRD) patterns for POEA in the powder form, we infer that the conducting islands are crystalline, and therefore a POEA film is believed to consist of conducting islands dispersed in an insulating, amorphous matrix. From conductivity measurements we inferred the charge transport to be governed by a typical quasi-one dimensional variable range hopping (VRH) mechanism. 相似文献
103.
Burada PS Schmid G Reguera D Vainstein MH Rubi JM Hänggi P 《Physical review letters》2008,101(13):130602
We present a novel scheme for the appearance of stochastic resonance when the dynamics of a Brownian particle takes place in a confined medium. The presence of uneven boundaries, giving rise to an entropic contribution to the potential, may upon application of a periodic driving force result in an increase of the spectral amplification at an optimum value of the ambient noise level. The entropic stochastic resonance, characteristic of small-scale systems, may constitute a useful mechanism for the manipulation and control of single molecules and nanodevices. 相似文献