Estimation of the Dimensions of Crystallites in a Xerogel of Superhigh Molecular Polyethylene

The length of straightened segments of macromolecules (SSM) in unconsolidated xerogels of superhigh molecular polyethylene, which turned out to attain 18 nm, was evaluated from the position of the band of longitudinal acoustic vibrations in a low–frequency Raman spectrum. The mean length of the straightened segments of macromolecules is equal to about 11 nm.     

A theoretical analysis of the coordination modes of CuII with penicillins: activation of the beta-lactam C-N bond.

The interaction of CuII with 6-formylamino-3alpha-carboxypenam and 6-acetylamino-3alpha-carboxypenam was investigated by means of DFT calculations with the UB3LYP functional. Nine different modes of complexation between CuII and 6-formylamino-3alpha-carboxypenam were located. When two water molecules directly bonded to CuII are included in the calculations on 6-acetylamino-3alpha-carboxypenam as penicillin model, only six CuII(H2O)2-6-acetylamino-3alpha-carboxypenam complexes (1S-6S) are found. In solution the four most stable complexes obtained from our calculations, 6S, 1S, 2S, and 3S, exhibit CuII in square-planar coordination with at least one bond to the carboxylate group, in agreement with experimental evidence. Complexes 6S, 1S, and 3S were previously suggested by available experimental evidence. In three of the most stable complexes (6S, 2S, and 3S) the beta-lactam C-N bond is remarkably activated and displays C-N bond lengths similar to those found in some tetrahedral intermediates located for the hydrolysis of 2-azetidinones. This suggests that these kinds of complexes belong to the reaction coordinate for the degradation of beta-lactam antibiotics in the presence of CuII.     

扫描隧道显微术中的微分谱学及其应用

文章介绍了扫描隧道显微术中微分谱学的原理及其在实验中的诸多应用。微分谱（dI／dV谱）和dI／dV成像可用来研究电子局域态密度在能量和空间的分布，即微分谱固定空间一点，反映电子态密度以能量为变量的分布；而dI／dV图像则反映某给定能量的电子局域态密度以空间为变量的分布，二次微分谱（d^2I／dV^2谱）和二次微分成像可以用来反映分子的非弹性隧穿过程，从而研究分子的振动态。     

腔调谐过程中激光器中两垂直偏振光的回馈特性

腔调谐过程中同时对HeNe激光器进行光回馈，设定回馈镜驱动信号的周期远小于腔调谐信号的周期，此时便获得腔调谐过程中谐振腔中两垂直偏振光的回馈信号. 回馈的形式分为仅垂直光回馈、仅平行光回馈以及两光同时回馈三种情况. 当两光同时回馈时，两模式间的模竞争较弱，两光回馈曲线有一定的相位差，该相位差小于180°，两光总体波动幅度变化趋势相反. 当仅单偏振光回馈时，两模式间的模竞争较强，两光回馈曲线始终反相，而且两光波动幅度变化趋势相同，此时可以将两光强度信号相减以实现成倍提高回馈信号幅度，从而提高系统灵敏度. 尤其仅垂直光回馈时，两光各自光强波动幅值都较大，并且在较大的增益曲线范围内保持光强波动幅值无明显变化，该特性可用于提高回馈系统的抗干扰能力，减少因激光功率漂移而引起的错误计数. 关键词： 自混合干涉 光回馈 模竞争 位移测量     

Electrodynamic Analysis of T-Shape Waveguide Junction Cells

An original cells for testing parameters of magnetodielectric materials are proposed. A rigorous electodynamic models for microwave signal transmission through such cell containing a sample being tested have been constructed. It has been found that maximum transmission coefficients are observed at frequencies of eigen and quasi-eigen modes depending on selected regime of the cell. Numerous experiments prove that the test cell in quasi-eigen mode regime is essentially more sensitive than in eigen one.     

Modulational instability of dust acoustic waves in a dusty plasma with nonthermal electrons and ions

Effects of nonadiabaticity of variable dust charge, dust fluid temperature, trapped electrons as well as nonisothermality of ions on the amplitude modulation of dust acoustic waves in an unmagnetized dusty plasma are investigated. A modified nonlinear Schr?dinger equation (NLSE) is obtained by the standard reductive perturbation technique and is solved numerically by the split-step Fourier method. The modulational instability and the envelope solitary wave structure are found to be modified somewhat by the effects of nonthermally distributed ions and trapped electrons.     

不同晶格光子晶体异质结的界面传导模

利用平面波展开方法与超原胞方法研究了两种不同晶格的光子晶体异质结的界面态. 这两种异质结都是在纯电介质背景上放置空气散射子. 一种异质结由正方形格子上放置正方形散射子和三角形格子上放置六角形散射子组成（SSTH异质结）. 另一种由长方格子上放置长方形散射子和三角形格子上放置圆形散射子组成（RRTC异质结）. 对于SSTH异质结，当沿着界面作晶格的横向拉开或者侧向滑移，都可产生界面态. 而对于RRTC异质结，无需从界面做晶格拉开或者侧向滑移就可产生界面传导模，这个结果有别于其他纯电介质光子晶体异质结的性质. 关键词： 光子晶体 异质结 传导模 超原胞     

Asymptotic and spectral properties of operator‐valued functions generated by aircraft wing model

The present paper is devoted to the asymptotic and spectral analysis of an aircraft wing model in a subsonic air flow. The model is governed by a system of two coupled integro‐differential equations and a two parameter family of boundary conditions modelling the action of the self‐straining actuators. The differential parts of the above equations form a coupled linear hyperbolic system; the integral parts are of the convolution type. The system of equations of motion is equivalent to a single operator evolution–convolution equation in the energy space. The Laplace transform of the solution of this equation can be represented in terms of the so‐called generalized resolvent operator, which is an operator‐valued function of the spectral parameter. More precisely, the generalized resolvent is a finite‐meromorphic function on the complex plane having a branch‐cut along the negative real semi‐axis. Its poles are precisely the aeroelastic modes and the residues at these poles are the projectors on the generalized eigenspaces. The dynamics generator of the differential part of the system has been systematically studied in a series of works by the second author. This generator is a non‐selfadjoint operator in the energy space with a purely discrete spectrum. In the aforementioned series of papers, it has been shown that the set of aeroelastic modes is asymptotically close to the spectrum of the dynamics generator, that this spectrum consists of two branches, and a precise spectral asymptotics with respect to the eigenvalue number has been derived. The asymptotical approximations for the mode shapes have also been obtained. It has also been proven that the set of the generalized eigenvectors of the dynamics generator forms a Riesz basis in the energy space. In the present paper, we consider the entire integro‐differential system which governs the model. Namely, we investigate the properties of the integral convolution‐type part of the original system. We show, in particular, that the set of poles of the adjoint generalized resolvent is asymptotically close to the discrete spectrum of the operator that is adjoint to the dynamics generator corresponding to the differential part. The results of this paper will be important for the reconstruction of the solution of the original initial boundary‐value problem from its Laplace transform and for the analysis of the flutter phenomenon in the forthcoming work. Copyright © 2004 John Wiley & Sons, Ltd.