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Finite element calculation is applied to assess elasticity parameters of random cellular structures with anisotropy. Cellular structure is generated using Random Sequential Addition algorithm. Anisotropy is considered by introducing elongation and orientation of ellipsoid voids. Structures are meshed using a regular mesh scheme. A uniaxial compression test is simulated under solid phase isotropy conditions. Effective Young's modulus and Poisson ratio are calculated and related to structural anisotropy parameters. Finite element results show a mesh-independence of elasticity parameters against scale and underline the large dependence of elasticity parameters to anisotropy and to the relative density of the cellular material: rigidity is increased in the anisotropy direction and mechanical instability in the other directions. Structures with large random population of ellipsoids contribute to lower such effect. [ABSTRACT FROM AUTHOR]

Summary: We report a normal-mode method for anisotropic refinement of membrane-protein structures, based on a hypothesis that the global near-native-state disordering of membrane proteins in crystals follows low-frequency normal modes. Thus, a small set of modes is sufficient to represent the anisotropic thermal motions in X-ray crystallographic refinement. By applying the method to potassium channel KcsA at 3.2 Å, we obtained a structural model with an improved fit with the diffraction data. Moreover, the improved electron density maps allowed for large structural adjustments for 12 residues in each subunit, including the rebuilding of 3 missing side chains. Overall, the anisotropic KcsA structure at 3.2 Å was systematically closer to a 2.0 Å KcsA structure, especially in the selectivity filter. Furthermore, the anisotropic thermal ellipsoids from the refinement revealed functionally relevant structural flexibility. We expect this method to be a valuable tool for structural refinement of many membrane proteins with moderate-resolution diffraction data. [Copyright &y& Elsevier]

The anisotropy of magnetic susceptibility (AMS) is a rapid and precise tool for determining paleowind directions. During the past several decades, AMS has been used for determining paleowind directions of Chinese bess. The AMS for a loess-paleosol profile in early Quaternary at Longdan in the Linxia Basin, Gansu Province, northeastern fringe of Qinghai-Xizang (Tibetan) Plateau has been obtained. The primary results show that the AMS of the Longdan profile has its typical normal eolian dust deposit. The AMS is mainly controlled by magnetic foliation (F) and the shape parameter of the AMS ellipsoid is oblate. The declination of maximum susceptibility (K1) was used to determine the paleowind direction of that area in early Quaternary and it was found that the paleowind direction is biased towards NW-SE. [ABSTRACT FROM AUTHOR]

Analysis of the parameters of anisotropic atomic displacements in various chemical compounds reveals a feature characteristic of a donor-acceptor bond: the ellipsoids of anisotropic displacements of the atoms involved in this bond are elongated in the direction of the bond. The explanation of the effect observed is proposed. [ABSTRACT FROM AUTHOR]