Adlayer Structures of DL-Homocysteine and L-Homocysteine Thiolactone on Au(111) Surface: an in situ STM Study

The adsorption Of DL-homocysteine (Hcy) and L-homocysteine thiolactone (HTL) on Au(1 1 1) electrode was investigated in 0.1 M HClO4 by cyclic voltammetry and in situ scanning tunneling microscopy (STM). Hcy and HTL molecules formed highly ordered adlayers on Au(1 1 1) surface. High-resolution STM images revealed the orientation and packing arrangement in the ordered adlayers. Hcy molecules formed (2root3 x 3root3)R30degrees adlayer structure and H-bonds between carboxyl groups were assumed to be responsible for the origin of tail-to-tail or head-to-head molecular arrangement, while HTL molecules formed (4 x 6) adlayer structure, and two different orientations and appearances in the ordered adlayer were found. Structural models were proposed for the two adlayers.

First-passage time of Duffing oscillator under combined harmonic and white-noise excitations

The first-passage time of Duffing oscillator under combined harmonic and white-noise excitations is studied. The equation of motion of the system is first reduced to a set of averaged Ito stochastic differential equations by using the stochastic averaging method. Then, a backward Kolmogorov equation governing the conditional reliability function and a set of generalized Pontryagin equations governing the conditional moments of first-passage time are established. Finally, the conditional reliability function, and the conditional probability density and moments of first-passage time are obtained by solving the backward Kolmogorov equation and generalized Pontryagin equations with suitable initial and boundary conditions. Numerical results for two resonant cases with several sets of parameter values are obtained and the analytical results are verified by using those from digital simulation.

Adsorption of His-tagged peptide to Ni, Cu and Au (100) surfaces: Molecular dynamics simulation

Molecular dynamics (MD) simulations are performed to study the interaction of His-tagged peptide with three different metal surfaces in explicit water. The equilibrium properties are analyzed by using pair correlation functions (PCF) to give an insight into the behavior of the peptide adsorption to metal surfaces in water solvent. The intermolecular interactions between peptide residues and the metal surfaces are evaluated. By pulling the peptide away from the peptide in the presence of solvent water, peeling forces are obtained and reveal the binding strength of peptide adsorption on nickel, copper and gold. From the analysis of the dynamics properties of the peptide interaction with the metal surfaces, it is shown that the affinity of peptide to Ni surface is the strongest, while on Cu and An the affinity is a little weaker. In MD simulations including metals, the His-tagged region interacts with the substrate to an extent greater than the other regions. The work presented here reveals various interactions between His-tagged peptide and Ni/Cu/Au surfaces. The interesting affinities and dynamical properties of the peptide are also derived. The results give predictions for the structure of His-tagged peptide adsorbing on three different metal surfaces and show the different affinities between them, which assist the understanding of how peptides behave on metal surfaces and of how designers select amino sequences in molecule devices design. (c) 2007 Elsevier Ltd. All rights reserved.

Chaos of liquid surface waves in a vessel under vertical excitation with slowly modulated amplitude

Free surface waves in a cylinder of liquid under vertical excitation with slowly modulated amplitude are investigated in the current paper. It is shown by both theoretical analysis and numerical simulation that chaos may occur even for a single mode with modulation which can be used to explain Gollub and Meyer's experiment. The implied resonant mechanism accounting for this phenomenon is further elucidated.

Dynamic-response of a laminated plate with friction damping

湍流不同尺度间的近程和共振作用规律及应用

从Navier-Stokes方程出发,研究了湍流不同尺度间的相互作用规律,给出相近尺度间近程粘性应力的积分和微分表达式.引入极相近尺度之间共振相互作用的概念,得到共振粘性应力的微分表达式.利用共振粘性应力张量获得不含经验关系和常数、近似封闭的大涡模拟(LES)方程组.利用近程和共振粘性应力张量获得不含经验关系和常数、近似封闭的湍流多尺度方程组.讨论了湍流多尺度方程的性质及用于湍流计算的优点,尺度间相互作用的近程特性说明:多尺度模拟是湍流计算很有价值的方法,并列举了算例.

A Wide Band Strong Acoustic Absorption in a Locally Network Anechoic Coating

Composite materials with interpenetrating network structures usually exhibit unexpected merit due to the cooperative interaction. Locally resonant phononic crystals (LRPC) exhibit excellent sound attenuation performance based on a periodical arrangement of sound wave scatters. Inspired by the interpenetrating network structure and the LRPC concept, we develop a locally network anechoic coating (LNAC) that can achieve a wide band of underwater strong acoustic absorption. The experimental results show that the LNAC possesses an excellent underwater acoustic absorbing capacity in a wide frequency range. Moreover, in order to investigate the impact of the interpenetrating network structure, we fabricate a faultage structure sample and the network is disconnected by hard polyurethane (PU). The experimental comparison between the LNAC and the faultage structure sample shows that the interpenetrating network structure of the LNAC plays an important role in achieving a wide band strong acoustic absorption.

A Dynamic Model For Ice-Induced Vibration Of Structures

A dynamic model for the ice-induced vibration (IIV) of structures is developed in the present study. Ice properties have been taken into account, such as the discrete failure, the dependence of the crushing strength on the ice velocity, and the randomness of ice failure. The most important prediction of the model is to capture the resonant frequency lock-in, which is analog to that in the vortex-induced vibration. Based on the model, the mechanism of resonant IIV is discussed. It is found that the dependence of the ice crushing strength on the ice velocity plays an important role in the resonant frequency lock-in of IIV. In addition, an intermittent stochastic resonant vibration is simulated from the model. These predictions are supported by the laboratory and field observations reported. The present model is more productive than the previous models of IIV.