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《Communications in Nonlinear Science & Numerical Simulation》2014,19(3):738-749
The dynamics of a third order phase locked loop (PLL) with a resonant low pass filter (LPF) has been studied numerically in the parameter space of the system. The range of stable synchronous operating zone of the PLL, expressed in terms of system and signal parameters, is estimated. The obtained results are in agreement with the analytically predicted results in the literature. The PLL dynamics in the unstable region is found to have a sequence of period doubling bifurcation and chaos. In the master–slave mode of operation of two 3rd order PLLs, the slave PLL can track the periodic as well as chaotic dynamics of the master PLL for a narrow range of effective frequency offset when other design parameters are within the stable zone as predicted for an isolated PLL. The synchronization of the master and slave PLLs in this condition is proved to be a generalized one using the auxiliary slave system approach. Experimental observations on prototype hardware circuits for an isolated PLL and for a master–slave PLL arrangement are also given. 相似文献
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A multi-function device based on two terahertz optical asymmetric demultiplexers (TOAD) is proposed,which can be used simultaneously as demultiplexing,data regeneration,clock recovery and wavelength conversion unit. The device can work at an ultra-high speed optical time-division multiplexing (OTDM) system with relatively low speed components. 相似文献
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A promising application of the multivariate curve resolution based on alternating least squares (MCR-ALS) method is reported for the analysis of the temperature-dependent conformational changes in poly(l-lysine) (PLL). The MCR-ALS approach has enabled detection of three structural components developed during the melting experiment. Most important is an infrared signature of the intermediate component described as a mixture of native α-helical conformation and its extended forms. 相似文献
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采用液相多肽合成法制备得到窄分子量分布、结构可控的生物相容性聚乙二醇嵌段共聚树枝状聚赖氨酸阳离子功能大分子(PEG-b-Dendritic PLL). 运用1H NMR核磁共振、凝胶电泳以及荧光淬灭滴定手段对所得阳离子两嵌段大分子的化学结构及其与质粒DNA (pDNA)结合作用与复合行为进行了研究. 结果表明聚乙二醇嵌段树枝状聚赖氨酸与pDNA分子可以在缓冲溶液中形成稳定的胶束, pDNA与阳离子树枝赖氨酸嵌段通过静电相互作用形成胶束核, 其水溶性聚乙二醇嵌段形成水溶性胶束壳, 提高了阳离子大分子/pDNA复合胶束的稳定性. 同时发现随着阳离子嵌段树枝状赖氨酸代数的增加, 阳离子两嵌段大分子与pDNA的结合作用增强, 有利于其作为基因转染生物功能载体的应用. 相似文献
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Siddharth V. Patwardhan Christina Raab Nicola Hüsing Stephen J. Clarson 《Silicon Chemistry》2005,2(5-6):279-285
Following recent investigations on the role of synthetic and biological macromolecules in silicification and biosilicification, we report here the bioinspired synthesis of silica structures under ambient conditions and neutral pH mediated by two synthetic macromolecules. In this research ethylene glycol modified silane (EGMS) was used as the silica precursor. The macromolecules used were either poly(allylamine hydrochloride) (PAH) or poly-l-lysine (PLL), both being cationically charged at neutral pH in an aqueous medium. Mild conditions that constitute the bioinspired or biomimetic synthesis were used to compare the behaviour of the EGMS to other silica precursors. The products were characterised by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Fourier Transform Infrared Spectroscopy (FTIR). The formation of well-defined spherical silica particles (for both PAH and PLL) and hexagons (for PLL only), was shown by electron microscopy. In addition, it was also found that these macromolecules were incorporated into the silica products, thus fulfilling the dual role of catalysts and structure directing agents in a similar fashion to that described in the literature for the formation of (bio)silica, as facilitated by (bio)macromolecules.This paper is dedicated to Mike Owen on occasion of his winning the DeBruyn medal, the first silicon chemist to do so. 相似文献
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Ch. Loppacher M. Bammerlin M. Guggisberg F. Battiston R. Bennewitz S. Rast A. Baratoff E. Meyer H. -J. Güntherodt 《Applied Surface Science》1999,140(3-4):287-292
This work presents constant amplitude Dynamic Force Microscopy (DFM) measurements under ultra-high vacuum conditions performed with home-built digital electronics based on the principle of phase locked loop (PLL) techniques. In DFM so-called topography is often measured in constant frequency shift (Δf) mode. This study describes the influence of phase shifts on constant Δf imaging. Therefore, phase variation experiments were acquired, leading to information about the cantilever resonance behaviour close to the surface. As sample, an evaporated thin film of NaCl on a Cu(111) substrate was chosen in order to obtain a heterogeneous system with clean Cu and NaCl areas. The atomic structure of both materials was resolved, which is the first time true atomic resolution was obtained on a metal. Large apparent topography variations are observed on this heterogeneous sample when changing the phase between the excitation and oscillation of the cantilever end. Such artefacts can be explained by comparison with phase variation experiments. 相似文献
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This paper reports the pH-induced structural changes in the surface immobilized poly(L-lysine)(PLL)film.Two-dimensional(2D) correlation analysis was applied to the Fourier transform infrared(FTIR)spectra of the surface-immobilized PLL film to examine the spectral changes induced by the alternations of the protonation state of the amino group in the side chain.Significant spectral changes in the FTIR spectra of the PLL film were observed between pH 7 and 8.The decrease in the protonation state of the amino group in the side chain induced spectral changes in the amino group as well as conformational changes in the alky]group in the side chain.From pH 1-8,the spectral changes in the amino and alkyl groups in the side chain occurred before those of the amide group in the main chain of the surface immobilized PLL film. 相似文献
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