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Unique Shape (unique + shape)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Gradient plasticity modelling of strain localization in granular materials

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2004
O. Al Hattamleh
Abstract The flow stress in the yield surface of plastic constitutive equation is modified with a higher order gradient term of the effective plastic strain to model the effect of inhomogeneous deformation in granular materials. The gradient constitutive model has been incorporated into the finite element code ABAQUS and used to simulate biaxial shear tests on dry sand. It is shown that the shape of the post-peak segment of the load displacement curve predicted by the numerical analysis is dependent on the mesh size when gradient term is not used. Use of an appropriate gradient coefficient is shown to correct this and predict a unique shape of the load displacement curve regardless of the mesh size. The gradient coefficient required turns out to be approximately inversely proportional to the mesh elemental area. Use of the strain gradient term is found to diffuse the concentration of plastic strains within shear band resulting in its consistent width. The coefficient of the higher gradient term appears as a function of the grain size, the mean confining stress, and the plastic softening modulus. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Template-directed synthesis of hybrid nanowires and nanorods

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2010
Jiayin Yuan
Abstract Recently, one-dimensional (1D) nanostructures, such as wires, rods, tubes, etc., have attracted considerable attention due to their unique shape- and size-dependant properties and many potential applications. Template-directed synthesis is a powerful and widely used method to prepare 1D objects. As robust unimolecular template, cylindrical polymer brushes have been exploited for the fabrication of various hybrid nanowires and nanorods, for instance, ,-Fe2O3, CdS, CdSe, TiO2, silica, Au, Te, etc. As a key advantage of this polymeric templating, the obtained 1D hybrid nanostructures are colloidally stable in solution, facilitating their further solution processing. Cryo-TEM image of organo-silica hybrid nanowires in aqueous solution (the inset shows a cartoon of the structure). [source]

Structure of TTHA1623, a novel metallo-,-lactamase superfamily protein from Thermus thermophilus HB8

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2009
Akihiro Yamamura
TTHA1623 is a metallo-,-lactamase superfamily protein from the extremely thermophilic bacterium Thermus thermophilus HB8. Homologues of TTHA1623 exist in a wide range of bacteria and archaea and one eukaryote, Giardia lamblia, but their function remains unknown. To analyze the structural properties of TTHA1623, the crystal structures of its iron-bound and zinc-bound forms have been determined to 2.8 and 2.2,Å resolution, respectively. TTHA1623 possesses an ,,,,-fold similar to that of other metallo-,-lactamase superfamily proteins with glyoxalase II-type metal coordination. However, TTHA1623 exhibits a putative substrate-binding pocket with a unique shape. [source]

3D Architectures of Iron Molybdate: Phase Selective Synthesis, Growth Mechanism, and Magnetic Properties

CHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2007
Yi Ding
Abstract Monoclinic and orthorhombic Fe2(MoO4)3 microsized particles with complex 3D architectures have been selectively prepared by a template-free hydrothermal process. The pH value, reaction time, temperature, and molybdenian source have crucial influence on the phase formation, shape evolution, and microstructures. Monoclinic Fe2(MoO4)3 particles obtained at pH,1 and pH,1.65 display ferromagnetic ordering at 10.4,K and 10.5,K, respectively, and the ferromagnetic component is determined to be 0.0458,,B and 0.0349,,B per Fe-ion at 10,K, respectively. For orthorhombic ,-Fe2(MoO4)3, antiferromagnetic ordering was observed about 12,K. At higher temperatures, ,-Fe2(MoO4)3 began to follow the Curie,Weiss law with ,=,70,K. Such 3D architectures of monoclinic and orthorhombic ,-Fe2(MoO4)3 microparticles with unique shapes and structural characteristics may find applications as catalysts and as well as in other fields. [source]