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991.
A phenomenological material law for pseudo elastic NiTi shape memory alloys (SMA) is presented. The model was derived from a thermodynamical framework and is well-suited to describe the thermomechanical coupled behaviour of the material. The material law, which was originally derived for small deformations, was extended to finite deformations using the Eulerian frame, in particular Hencky's logarithmic strain and the logarithmic rate. A first emphasis is on the physical interpretation of the material parameters and their identification. A second focus lies in the presentation of a structural example for the implementation of the material law into a commercial Finite Element code. Additionally a comparison of the numerical and experimental data of the presented example is performed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
992.
Feng Xu Elizabeth J. Golightly Palle Schneider Randy M. Berka Kimberly M. Brown James A. Johnstone Denise H. Baker Claus C. Fuglsang Stephen H. Brown Allan Svendsen Alan V. Klotz 《Applied biochemistry and biotechnology》2000,88(1-3):23-32
The Fusarium spp. (Dactylium dendroides) galactose oxidase was expressed in Aspergillus oryzae and Fusarium venenatum hosts. Under the control of an A. niger α-amylase or a Fusarium trypsin promoter, high level galactose oxidase expression was achieved. The recombinant oxidase expressed in the A. oryzae host was purified and characterized. The purified enzyme had a molecular weight of 66 k Da on sodium dodecyl sulfate-polymerase
gel electrophoresis (SDS-PAGE) and 0.4 mol copper atom per mole protein. The stoichiometry increased to 1.2 after a Cu saturation.
Based on a peroxidase-coupled assay, the enzyme preparation showed an activity of 440 turnover per second toward d-galactose (0.1 M) at pH7 and 20°C. The enzyme had an optimal temperature of 60°C at pH 6.0 and an activation free Gibbs energy of 33 kJ/mol.
A series of d-galactose derivatives was tested as the reducing substrate for the oxidase. The difference in activity was interpreted by
the stereospecificity of the oxidase toward the substituents in the pyranose substrate, particularly on the C5 and the cyclic
hemiacetal O sites. The recombinan toxidase could act on some galactose-containing polysaccharides, such as guar gum, but
was not able to oxidize several common redox compounds that lacked a primary alcohol functional group. 相似文献
993.
994.
We present and contrast two distinct ways of including extremal black holes in a Lorentzian Hamiltonian quantization of spherically symmetric Einstein-Maxwell theory. First, we formulate the classical Hamiltonian dynamics with boundary conditions appropriate for extremal black holes only. The Hamiltonian contains no surface term at the internal infinity, for reasons related to the vanishing of the extremal hole surface gravity, and quantization yields a vanishing black hole entropy. Second, we give a Hamiltonian quantization that incorporates extremal black holes as a limiting case of nonextremal ones, and examine the classical limit in terms of wave packets. The spreading of the packets, even the ones centered about extremal black holes, is consistent with continuity of the entropy in the extremal limit, and thus with the Bekenstein-Hawking entropy even for the extremal holes. The discussion takes place throughout within Lorentz-signature spacetimes. 相似文献
995.
996.
Justin Wolf Wolfram Stüer Claus Grünwald Helmut Werner Peter Schwab Michael Schulz 《Angewandte Chemie (International ed. in English)》1998,37(8):1124-1126
An active role is played by MgCl2 during the conversion of the vinylidene precursor 2 into carbenes 3 (R=H, Ph; L=P(C6H11)3). These complexes can be prepared in a convenient and very efficient one-pot synthesis and have a catalytic activity in metathesis comparable to that of Grubbs compound (Ph instead of CH2R). 相似文献
997.
George R. Newkome Claus D. Weis Charles N. Moorefield Gregory R. Baker Bradley J. Childs Jon Epperson 《Angewandte Chemie (International ed. in English)》1998,37(3):307-310
Used individually or combinatorially , unique isocyanate-based dendritic monomers generate homo- and heterofunctional materials (the sketch shows schematically a molecule with a heterofunctional surface). Tier construction by combinatorial monomer addition offers new avenues to macromolecular architectural design and the control of physical properties. 相似文献
998.
Claus Leggewie 《Chemie in Unserer Zeit》2003,37(6):410-415
In a fictitious meeting between the chemist and agricultural reformer Justus Liebig and the poet and social revolutionary Georg Büchner alternative paths of historical development in the early 19th century as well as current developments in food engeneering are discussed. 相似文献
999.
The application of Particle Image Velocimetry (PIV) to measurement of flows on large scales is a challenging necessity especially
for the investigation of convective air flows. Combining helium filled soap bubbles as tracer particles with high power quality
switched solid state lasers as light sources allows conducting PIV on scales of the order of several square meters. The technique
was applied to mixed convection in a full scale double aisle aircraft cabin mock-up for validation of Computational Fluid
Dynamics simulations. 相似文献
1000.
Jürgen-Hinrich Fuhrhop Claus Endisch Uwe Bindig Bianca Rosengarten Christoph Bttcher Ulrich Siggel Eishun Tsuchida Teruyuki Komatsu 《Macromolecular Symposia》1996,105(1):27-42
Amphiphilic metalloporphyrins assemble in water to form supramolecular fibers, which have been characterized by transmission electron microscopy. Loose octopus porphyrin fibers can be doped with hydrophobic electron acceptors, metalloporphyrin monomolecular sheets are crystalline. Charge separation occurs in amino porphyrin fibers without added electron acceptors. Bolaamphiphilic porphyrins with four pyridinyl or methyl pyridinium groups in β-pyrrolic positions have been synthesized. The regioisomer mixture is very soluble in water (≌ 0.1 M) and is ideally suited to form heterodimers with negatively charged ms-tetrasubstituted porphyrins. Bimetallic porphyrinate pairs are described. The zinc complex is stable down to pH 1.0. Regioisomer II forms well-defined molecular monolayer leaflets in bulk water at pH 2.5. The surface structure of such monolayers is discussed. It consists of a large cationic plane and hydrophobic edges. Possible applications are discussed shortly. 相似文献