Darstellung und Charakterisierung von Iodoplatinaten MexNH4–xPtI4 (x = 2 − 4), gemischtvalenten Octaiododiplatinaten(II,IV) mit Pt2I8-Baugruppen

Preparation and Characterization of Iodoplatinates Me_xNH_4–xPtI₄ (x = 2–4), Mixed Valence Octaiododiplatinates(II,IV) with Pt₂I₈ Groups Iodoplatinates APtI₄ (A = Me_xNH_4–x with x = 2–4) have been prepared by partial oxidation of the correspondent hexaiododiplatinates(II) A₂Pt₂I₆ with I₂ in methanolic solutions. X-ray structure analyses of the bronze-coloured needle-shaped crystals of the compounds showed rows of dinuclear anions Pt₂I₈^2?, built up by edgesharing planar PtI₄ groups with Pt^II und octahedral PtI₆ groups with Pt^IV. The different space requirement of the cations leads to the formation of three different structures. Within the anion stacks weak intermolecular Pt^IV? I …? Pt^II interactions are detectable by Raman spectroscopy.     

Implementation of an algorithm for detecting patterns in defocused scenes using binary joint transform correlation

An original method to detect images in defocused scenes by means of a binary joint transform correlation is presented. Defocused images are described in frequency domain as the product between the Fourier transform of the in-focus scene by the optical transfer function of the imaging lens. This function, which presents positive and negative values, introduces sign errors in the joint power spectrum. The goal of this study is to detect the sign of the optical transfer function starting from the defocused image by means of a digital algorithm. Information provided by the algorithm allows to compensate the sign errors in the binary joint power spectrum and to obtain invariant correlations with respect to defocusing. Theoretical analysis and digital experiments to test the procedure are provided.     

用光学相关识别方法测量单模光纤的折射率分布和色散

介绍了一种测量单模光纤剖面折射率分布和色散的新方法－－光学相关识别方法。应用计算全息制作高斯－拉盖尔模的匹配滤波器，根据光学相关识别原理测出单模光纤场分布的展开系数，由此推得剖面折射率分布和色散，给出了实际测量结果。     

2D CP/MASC Isotropic Chemical Shift Correlation Established byH Spin Diffusion

A new 2D solid-state CP/MAS¹³C NMR exchange experiment for through-space isotropic chemical shift correlation is proposed and demonstrated. Through-space correlation is established via a second cross polarization from¹³C to¹H and subsequent¹H spin diffusion. A third cross polarization results in the final¹³C–¹³C isotropic chemical shift correlation. The¹H spin diffusion time is a variable parameter allowing different mean square magnetization displacements to be probed. Experimental results on mixtures of differently¹³C-labeled alanine and polyethylene indicate that this site-selective 2D technique can be used to characterize domain sizes and proximities over a wide range of length scales (1–200 nm) in solids such as polymers or biological materials.     

Elasticity theory of a twisted stack of plates

We present an elastic model of B-form DNA as a stack of thin, rigid plates or base pairs that are not permitted to deform. The symmetry of DNA and the constraint of plate rigidity limit the number of bulk elastic constants contributing to a macroscopic elasticity theory of DNA to four. We derive an effective twist-stretch energy in terms of the macroscopic stretch along and relative excess twist about the DNA molecular axis. In addition to the bulk stretch and twist moduli found previously, we obtain a twist-stretch modulus with the following remarkable properties: 1) it vanishes when the radius of the helical curve following the geometric center of each plate is zero, 2) it vanishes with the elastic constant K₂₃ that couples compression normal to the plates to a shear strain, if the plates are perpendicular to the molecular axis, and 3) it is nonzero if the plates are tilted relative to the molecular axis. This implies that a laminated helical structure carved out of an isotropic elastic medium will not twist in response to a stretching force, but an isotropic material will twist if it is bent into the shape of a helix. Received: 4 July 1997 / Received in final form: 16 October 1997 / Accepted: 21 October 1997     

Software for interpolating and modelling unknown functions

Software has been developed for fitting a stochastic process model to multi-dimensional data. Applications include contouring, cross-section plotting and optimization. The behaviour of the variance and the gradient of the interpolating function in the near neighbourhood of closely adjacent data points has been investigated.     

关于核多体系统的基态关联效应

对于一个原子核模型系统在不同耦合强度、不同粒子数情况下的基态关联效应进行了研究,结果表明：当具有稳定的静态形变时,基态关联基本上可用基于静态上的零点振动来解释,因此,关于静态性质的自治场计算是至关重要的. 但在开始发生单极形变的临界点附近,它随控制参量的变化显得很复杂、很敏感. 看来,在滴线附近的轻核的进一步研究中,关联效应是需要注意考虑的.     

From σ to π Coordination: Tetraisopropylcyclopentadienyl dichlorides [(C5HR4)ECl2] (R = CHMe2) of phosphorus,arsenic, antimony,and bismuth

[(C₅HR₄)PCl₂] ( 1a ), [(C₅HR₄)PBr₂] ( 1 b ), [(C₅HR₄)AsCl₂] ( 2 ), and [(C₅HR₄)SbCl₂] ( 3 ), have been obtained from the corresponding pnicogen trihalides and sodium tetraisopropylcyclopentadienide (R = CHMe₂). The molecular structures of 1, 2 , and 3 as well as the related structure of [(C₅HR₄)BiCl₂] ( 4 ) display increasing π character of hetero atom to cyclopentadienyl bonding with increasing metallic character of the hetero atom.     

Correlation functions in the cavity model of ionic fluids

The dominant long-range contribution of the solute-solvent interaction to ion-ion distribution functions is assessed in a limit that yields the cavity model of ionic solutions.This paper is based upon a presentation given at the 71st Statistical Mechanics Meeting, May 1994.