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101.
Zhishan Bo Jürgen P. Rabe A. Dieter Schlüter 《Angewandte Chemie (International ed. in English)》1999,38(16):2370-2372
Langmuir monolayers are formed from an amphiphilically decorated poly(para-phenylene), which indicates that its hydrophilic and hydrophobic parts segregate lengthwise along the polymer backbone in this nanometer-sized cylinder as illustrated in A . This polymer differs from known amphiphiles in that it consists of a linear, covalently bound sequence of “little” amphiphiles. It is much more rigid than common “polysoaps”, which should increase its potential to aggregate, for example, into channels. 相似文献
102.
103.
ZrIV and TaV Complexes with Methano‐Bridged Bis(aryloxy) Ligands The bis(aryloxy) ligand precursor compounds bis(2‐trimethylsiloxy‐5‐tbutylphenyl)methane (L–SiMe3) and its bromoderivative (2‐trimethylsiloxy‐3‐bromo‐5‐tbutylphenyl)(2′‐trimethylsiloxy‐5′‐tbutylphenyl)methane (LBr–SiMe3) are prepared in analogy to the corresponding calixarenes in excellent yields. X‐ray structure analysis for LBr–SiMe3: space group P21/c, a = 12.462(7), b = 10.466(6), c = 23.315(14) Å, β = 105.02(4)°, V = 2937(3) Å3, Z = 4. L–SiMe3 and LBr–SiMe3 react with ZrIV and TaV chlorides in very good yields forming di‐ and trinuclear complexes. From the reaction of CpZrCl3 with LBr–SiMe3 in the ratio of 3 : 2 a Zr3 complex ( 7 ) is obtained, with one LBr ligand only, which Zr atoms are bridged by a μ3‐oxygen. The X‐ray structure analysis of 7 (space group R 3, a = 33.23(6), c = 24.47(8) Å, V = 23405(128) Å3, Z = 18) additionally reveals that one phenolato oxygen atom of the LBr ligand is terminally bound to a distorted tetragonal‐pyramidal coordinated Zr atom, while the second phenolato oxygen atom of the LBr ligand forms a bridge to another Zr atom with a distorted octahedral coordination. The third Zr atom is also found in a distorted octahedral coordination mode. The reactions of L–SiMe3 and LBr–SiMe3 with CpTaCl4 and TaCl5 yield dinuclear Ta complexes with a bridging bis(aryloxy) ligand. NMR spectroscopic data point out that the coordination of the bis(aryloxy) ligands in the Ta complexes very much resembles that in the Zr3‐complex with one terminal and one bridging phenolato oxygen atom. The Zr3 and the Ta complexes LBrTa2Cp2Cl6 and LTa2Cl8 were tested with respect to their catalytic properties in olefin polymerisation reactions in the presence of MAO. 相似文献
104.
105.
Summary. We employ a data-sparse, recursive matrix representation, so-called -matrices, for the efficient treatment of discretized integral operators. We obtain this format using local tensor product interpolants of the kernel function and replacing high-order approximations with piecewise lower-order ones. The scheme has optimal, i.e., linear, complexity in the memory requirement and time for the matrix-vector multiplication. We present an error analysis for integral operators of order zero. In particular, we show that the optimal convergence (h) is retained for the classical double layer potential discretized with piecewise constant functions.Corrigendum This revised version was published online in February 2005 due to typesetting mistakes in the author correction process. 相似文献
106.
Quantitative determination of contact stiffness using atomic force acoustic microscopy 总被引:1,自引:0,他引:1
Atomic force acoustic microscopy is a near-field technique which combines the ability of ultrasonics to image elastic properties with the high lateral resolution of scanning probe microscopes. We present a technique to measure the contact stiffness and the Young's modulus of sample surfaces quantitatively, with a resolution of approximately 20 nm, exploiting the contact resonance frequencies of standard cantilevers used in atomic force microscopy. The Young's modulus of nanocrystalline ferrite films has been measured as a function of oxidation temperature. Furthermore, images showing the domain structure of piezoelectric lead zirconate titanate ceramics have been taken. 相似文献
107.
P. Joos A. Ladage H. Meyer D. Notz P. Stein G. Wolf S. Yellin C. Benz G. Drews D. Hoffmann J. Knobloch W. Kraus H. Nagel E. Rabe C. Sander W.-D. Schlatter H. Spitzer K. Wacker K. Smith 《Physics letters. [Part B]》1974,52(4):481-484
The Q2 dependence of σ (γvp→π?Δ++) was measured. Close to threshold σ (γvp→π?Δ++) is roughly proportional to 1/(m2? + Q2)2. The data are consistent with dominance of the contact term and imply that the contact term has the Q2 dependence of the ? propagator. 相似文献
108.
109.
Binary phase transmission gratings exhibiting a certain number N of central diffraction orders of equal intensity can be used to construct star couplers of the 1-to-N and N-to-N type. The calculation of the grating's groove structure is described, and first experimental results are presented. 相似文献
110.
Two optical multiplex arrangements for pattern recognition are compared. In the first system the Fourier spectrum of an object transparency is optically multiplied for parallel processing with a matrix of different holographic Fourier filters. In the other arrangement the spectrum of the object transparency is switched time sequentially by means of a light beam deflector onto different filters in the Fourier plane. In comparison the time sequential method appears better adapted for high information content. 相似文献