The correlation function in Wilson's theory of phase transitions: Above and below the transition

The correlation function and the correlation length are discussed in the theoretical framework of the Wilson-Feynman diagram expansion for small =4–d. It is shown explicitly that to order ² the scaling relation = (2–) is satisfied and that the correlation function is a homogeneous function ofk and . The explicit form of the scaled correlation function is exhibited.     

Monitoring microstructural material changes in paper through microscopic speckle correlation rate measurements

A system for real-time digital speckle correlation rate measurements is developed and applied on printing paper in the micro-scale. The system consists of a continuous laser and a CCD camera connected to a PC. To measure on objects in the micro-scale the system is connected to a stereomicroscope where one of the channels is used for imaging and the other channel is used for illumination of the object surface. The system is evaluated through measurements on printing paper over an area of 1 mm² and with a spatial resolution of 30 μm on the object. The results show that the system is able to monitor the dynamics in paper during both wetting and drying in real-time over a time scale ranging from one-tenth of a second to several hours.     

Simultaneous analysis of two or more samples on the same chromatographic column

Summary Pseudo random binary and ternary sequences (PRBS and PRTS) have already been used to identify impulse responses of linear systems—in particular, we have shown [1,2], how decorrelation techniques allow the chromatogram of a given sample to be obtained by injecting the product following a PRBS or PRTS law. In this paper an additional difficulty is overcome by injecting in parallel two different samples onto one column, then obtaining simultaneously but separately the two chromatograms by use of numerical decorrelation. We present the theoretical justification and the result of numerical simulation in the case of a pseudo random ternary sequence injection law. A successful experiment on an actual chromatograph using a pseudo random binary sequence injection law is presented.     

过渡金属核磁共振谱

以数种过渡金属的核磁共振研究介绍了有关技术在近年的发展;内容集中于如何从图谱取得化学信息。讨论分为固体谱与液体谱两部分,固体谱会着重谱线的分析,液体谱则集中对有关化学位移的理论解释。     

X-Ray Photon Correlation Spectroscopy at the European X-Ray Free-Electron Laser (XFEL) facility

The proposed European X-ray Free-Electron Laser source (XFEL) will provide extremely brilliant (B>10³³ ph/s/mm²/mrad²/0.1% bw) and highly coherent X-ray beams. Due to the pulse structure and the unprecedented brightness one will be able for the first time to study fast dynamics in the time domain, thus giving direct access to the dynamic response function S(Q,t), instead of S(Q,ω), which is of central importance for a variety of phenomena such as fast non-equilibrium dynamics. X-ray Photon Correlation Spectroscopy (XPCS) measures the temporal changes in a speckle pattern produced when coherent light is scattered by a disordered system and therefore allows the measurement of S(Q,t). This article summarizes important aspects of the scientific case for an XPCS instrument at the planned XFEL. New XPCS setups taking account of the XFEL pulse structure are described. To cite this article: G. Grübel, C. R. Physique 9 (2008).     

基于改进SUSAN算法的箭环目标跟踪与测量

针对发射场火箭初始段漂移量的测量，提出一种带灰度梯度方向的SUSAN算子，实现了基于该算子与变模板相关跟踪算法的目标跟踪测量方法.首先在SUSAN特征检测原则的基础上，将对角点的检测转化为对边缘的检测，同时记录梯度方向，在剔除了图像噪音点之后，由具有特定方向信息的边缘像素点精确定位角点的坐标.该方法克服了标准SUSAN算法准确度低的弊病，使得对目标的提取准确度可以达到亚像素级，并增强了抗噪性能，实验证明该算法提取准确性高，运算量小，易于实现.     

Spectral and network methods in the analysis of correlation matrices of stock returns

Correlation matrices inferred from stock return time series contain information on the behaviour of the market, especially on clusters of highly correlating stocks. Here we study a subset of New York Stock Exchange (NYSE) traded stocks and compare three different methods of analysis: (i) spectral analysis, i.e. investigation of the eigenvalue-eigenvector pairs of the correlation matrix, (ii) asset trees, obtained by constructing the maximal spanning tree of the correlation matrix, and (iii) asset graphs, which are networks in which the strongest correlations are depicted as edges. We illustrate and discuss the localisation of the most significant modes of fluctuation, i.e. eigenvectors corresponding to the largest eigenvalues, on the asset trees and graphs.     

Comprehensive Basicity Scales for N‐Heterocyclic Carbenes in DMSO: Implications on the Stabilities of N‐Heterocyclic Carbene and CO2 Adducts

A very broad acidity scale (≈40 pK units) for about 400 N‐heterocyclic carbene precursors (NHCPs) with various backbones and electronic features, including imidazolylidenes, 1,2,4‐triazolylidenes, cyclic diaminocarbenes (CDACs), diamidocarbenes (DACs), thiazolylidenes, cyclic (alkyl)(amino)carbenes (CAACs) and mesoionic carbenes (MICs), was established in DMSO by a well examined computational method. Varying the backbone structure or flanking N‐substituents can have different extent of acidifying effects, depending on both the nature and number of substituent(s). The Gibbs energies (ΔG_rs) for the reactions between the corresponding NHCs and CO₂ were also calculated. There is a good linear correlation between the pK_as of most NHCPs and ΔG_rs, suggesting that a greater basicity of NHC leads to a more stable NHC‐CO₂ adduct. Interestingly, the nearby asymmetric environment has virtually no differential effect on the acidities of the chiral NHCP enantiomers, but has a pronounced effect on the ΔG_r values.     

统计相关性分析方法的进展

系统综述了自19世纪开始且至今常用统计相关性的方法,例如Pearson和Spearman相关系数,CorGc和CovGc 相关性及距离相关性方法。重点介绍了2011年提出的MIC方法以及由此引发的毁誉参半的大量评述,旨在揭示这一热点领域研究面貌。该领域不仅受到统计学家的关注,而且受到了分析大样本和异质数据的应用研究领域的学者们的追捧,例如基因组生物学家和网络信息研究者。这些研究者期望在众多已有方法的理解和剖析中更恰当地付诸应用,并提出新的应用问题来推动新的分析方法的创造。