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971.
Holger Stephan Dietmar Appelhans Daniela Tabuani Brigitte Voit 《Tetrahedron letters》2005,46(18):3209-3212
Two novel star-like cyclam derivatives appended with four amino groups and four PEG-arms have been synthesised. The complex formation of cyclam and the two cyclam derivatives with Cu(II) has been studied by UV-vis and time-resolved laser-induced fluorescence (TRLFS) measurements outlining 1:1 complexes between cyclam ligands and Cu(II). By TRLFS measurements a quench effect of the Cu(II) on the fluorescence of the ligand was also found to determine the complex formation between Cu(II) and the ligands. 相似文献
972.
973.
What organization of condensed matter does resist irradiation, as a function of irradiation conditions? How to characterize the latter? We survey the advances in the field during the past three decades, when irradiation effects reduce to nuclear collisions. While in simple cases (structure defined by a scalar order parameter) one may define a stochastic potential, which yields the stationary states of the compounds under irradiation and their respective stability, in more general cases, we are left with brute force atomistic simulations to explore materials' behaviour as a function of irradiation conditions. Special attention is given to the kinetics of concentration fields under irradiation, a question with several practical implications. We conclude that irradiation conditions are best defined by three parameters: the cascade features (number of displacements and replacements, length of replacement sequences, …), the frequency of cascade occurrence, and the cumulated dose. We suggest cascade features be named ‘(elementary) dose’ and the cascade occurrence frequency ‘dose rate’. To cite this article: G. Martin, P. Bellon, C. R. Physique 9 (2008). 相似文献
974.
975.
John Ferdinands 《Topology and its Applications》1991,40(3):221-231
A finite CW complex X is said to be prime if, given a Hurewicz fibration F→E→B with E homotopy equivalent to X, and B and F homotopy equivalent to finite CW complexes, either B or F is contractible. We show that certain 3- and 4-plane complex Grassmanian manifolds are prime. 相似文献
976.
We obtain the existence of a cohomological obstruction to expressing N=2 line bundles as tensor products of N=1 bundles. The motivation behind this paper is an attempt at understanding the N=2 super KP equation via Baker functions, which are special sections of line bundles on supercurves. 相似文献
977.
978.
Isabel?Díez Klaus?TauerEmail author Burkhard?Schulz 《Colloid and polymer science》2004,283(2):125-132
A comprehensive study gives experimental evidence that a complex made from pyrrole and -naphthalenesulfonic acid in a molar composition of 3:1 acts as morphological precursor in the subsequent oxidative polymerization of pyrrole initiated with ammonium peroxodisulfate. The precursor complex itself is unable to polymerize but its outer parallelepipedal shape with a high aspect ratio is templated in the inner surface of the formed conducting polypyrrole tubes. 相似文献
979.
逆向工程技术作为一门新兴学科在复杂模型建模方面具有独特优势,并在许多领域得到了广泛的应用,在此基础上本文首次提出了基于逆向工程的三维复杂地质体精细建模技术,使得建立模型达到既“可视”又“可算”的目的。利用现行大型通用有限元仿真平台(ABAQUS,AD INA,ANSYS等)良好的网格划分功能且具有与CAD /CAM软件有着良好的接口这一优点,对模型进行网格划分,然后转换为FLAC3D能够接受的格式,从而克服了FLAC3D在前处理建模方面的不足。以AD INA为例对相应的接口程序开发过程进行了阐述,将上述技术方法应用于工程实例,取得了很好的效果。 相似文献
980.
Many instruments used to measure viscoelastic properties are only capable of subjecting a sample to a limited range of loading
frequencies. For thermorheologically simple materials, it is assumed that a change in temperature is equivalent to a shift
of the viscoelastic behavior on the log frequency or time axis. For many materials, time–temperature superposition appears
to work well for modulus or compliance curves over three decades of time or frequency, but some deviations are known if the
window is expanded to five or six decades. To apply a more stringent test of the validity of time–temperature superposition,
broadband viscoelastic spectroscopy is used to isothermally study polymethylmethacrylate and low-density polyethylene at several
temperatures in the glassy region. Shear modulus and damping (tan δ) are measured isothermally over a wide range (up to 11 decades) of time and frequency. Results indicate that, while modulus
curves can be approximately superimposed, the damping (tan δ) curves change in height and shape with temperature. 相似文献