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Bending Energy (bending + energy)
Selected AbstractsA morphometric approach to the geographic variation of the terrestrial isopod species Armadillo tuberculatus (Isopoda: Oniscidea)JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2009M. Kamilari Abstract The terrestrial isopod species Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) is a widely polymorphic species distributed in the south-central Aegean region (Greece) with a different morph on each island. Variation consists in coloration, size of cuticular tubercules, shape of telson and the shape of the male first pleopod exopodite (secondary sexual character of taxonomic importance). We studied the allometric growth of a cuticular tubercule in 17 populations (for both male and female individuals) and the shape variation of the first male pleopod exopodite in 10 populations using Elliptic Fourier Analysis, in order to test for patterns of intraspecific variation and possible relationships between morphs. In addition, Thin Plate Spline analysis was used for the calculation of the minimum bending energy between different exopodite shapes, which was then used for estimating the minimum spanning network (MSN) connecting them. The different allometric growth rates of the tubercule among island groups were significantly related to island latitude and climatic factors. On the other hand, the clustering of islands and the MSN based on male exopodite shape differences were not related to the palaeogeography of the Aegean region or to the present geographic distances of islands. These results are interpreted as evidence for non-adaptive radiation of the morphs. Resumen El isópodo terrestre Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) es una especie extensamente polimórfica distribuida por la región sur-central del piélago Egéo (Grecia), con una forma distinta en cada isla. Se trata de variaciones en la coloración, el tamaño de los tubérculos cuticulares y en la forma del primer exopodio masculino del pleopodo (carácter sexual secundario de importancia taxonómica). Estudiamos el crecimiento alométrico del tubérculo cuticular en 17 poblaciones (en individuos de ambos sexos) y la variación de la forma del primer exopodio masculino del pleopodo en 10 poblaciones según el análisis de Fourier elíptico (Elliptic Fourier Analysis) para detectar patrones de variación intraespecifica y relaciones posibles entre las formas de la especie. Además, el análisis Thin Plate Spline fue utilizado para el cálculo de la Energía de Flexión Mínima (Minimum Bending Energy) entre diversas formas del exopodio, que entonces fue utilizada para estimar la Mínima Red de Distancias (Minimum Spanning Network, MSN) que las conectaba. Detectamos una correlación significativa entre las diversas tasas de crecimiento alométrico del tubérculo entre los grupos de islas y la latitud de la isla. Por otro lado, la agrupación de las islas y la MSN, basada en las diferencias de la forma del exopodio, no fueron relacionados con la paleogeografía de la región del piélago Egéo ni con las actuales distancias geográficas de las islas. Estos resultados se interpretan como evidencia para la radiación non-adaptativa de las diversas formas de la especie. [source] Dual-mixed p and hp finite elements for elastic membrane problemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2002E. BertótiArticle first published online: 26 OCT 200 Abstract A complementary energy-based, dimensionally reduced plate model using a two-field dual,mixed variational principle of non-symmetric stresses and rotations is derived. Both the membrane and bending equilibrium equations, expressed in terms of non-symmetric mid-surface stress components, are satisfied a priori introducing first-order stress functions. It is pointed out that (i) the membrane-, shear- and bending energies of the plate written in terms of first-order stress functions are decoupled, (ii) although unmodified 3-D constitutive equations are applied, the energy parts do not contain the 1/(1-2,) term for isotropic, linearly elastic materials. These facts mean that the finite element formulation based on the present plate model should be free from shear locking when the thickness tends to zero and free from incompressibility locking when the Poisson ratio , converges to 0.5, irrespective of low-order h -, or higher-order p elements are used. Curvilinear dual-mixed hp finite elements with higher-order stress approximation and continuous surface tractions are developed and presented for the membrane (2-D elasticity) problem. In this case the formulation requires the approximation of three independent variables: two components of a first-order stress function vector and a scalar rotation. Numerical performance of three quadrilateral dual,mixed elements is presented and compared to displacement-based hp finite elements when the Poisson ratio converges to the incompressible limit of 0.5. The numerical results show that, as expected, the dual,mixed elements developed in this paper are free from locking in the energy norm as well as in the stress computations, for both h - and p -extensions. Copyright © 2001 John Wiley & Sons, Ltd. [source] Planarity of acetamides, thioacetamides, and selenoacetamides: Crystal structure of N,N -dimethylselenoacetamideHETEROATOM CHEMISTRY, Issue 4 2002Shuqiang Niu The planarity of acetamides 1a,3a, thioacetamides 4a,6a, and selenoacetamides 7a,9a, R1R2NC(=E)CH3 where E = O, S, Se, and R1, R2 = H or CH3, was investigated using theoretical calculations at the density functional theory (DFT) level. The calculations showed that the methyl substitution on nitrogen and the change from the amide moiety (NCO) to NCS or NCSe group increased the double bond character of the NC bond. In other words, the planarity of these compounds (1a,9a) increases in the order NH2 < NHCH3 < N(CH3)2 and O < S < Se. The calculations of bending energy suggest that the planar geometry represents the lowest energy conformation for all compounds investigated in this work. N,N-Dimethyl-selenoacetamide (9a), (CH3)2NC(Se) CH3, has the largest bending energy of 10.37 kcal/mol, which suggests that it possesses the greatest planarity among the compounds 1a,9a. However, the solid phase molecular structure of 9a was found to be slightly nonplanar by X-ray crystallography. The slight nonplanarity observed experimentally is very likely the consequence of intermolecular interactions arising within the crystal packing. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:380,386, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10056 [source] Accurate eight-node hexahedral elementINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2007Magnus Fredriksson Abstract Based on the assumed strain method, an eight-node hexahedral element is proposed. Consistent choice of the fundamental element stiffness guarantees convergence and fulfillment of the patch test a priori. In conjunction with a ,-projection operator, the higher order strain field becomes orthogonal to rigid body and linear displacement fields. The higher order strain field in question is carefully selected to preserve correct rank for the element stiffness matrix, also for distorted elements. Volumetric locking is also removed effectively. By considerations of the bending energy, improved accuracy is obtained even for coarse element meshes. The choice of local co-ordinate system aligned with the principal axes of inertia makes it possible to improve the performance even for distorted elements. The strain-driven format obtained is well suited for materials with non-linear stress,strain relations. Several numerical examples are presented where the excellent performance of the proposed eight-node hexahedral is verified. Copyright © 2007 John Wiley & Sons, Ltd. [source] A morphometric approach to the geographic variation of the terrestrial isopod species Armadillo tuberculatus (Isopoda: Oniscidea)JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2009M. Kamilari Abstract The terrestrial isopod species Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) is a widely polymorphic species distributed in the south-central Aegean region (Greece) with a different morph on each island. Variation consists in coloration, size of cuticular tubercules, shape of telson and the shape of the male first pleopod exopodite (secondary sexual character of taxonomic importance). We studied the allometric growth of a cuticular tubercule in 17 populations (for both male and female individuals) and the shape variation of the first male pleopod exopodite in 10 populations using Elliptic Fourier Analysis, in order to test for patterns of intraspecific variation and possible relationships between morphs. In addition, Thin Plate Spline analysis was used for the calculation of the minimum bending energy between different exopodite shapes, which was then used for estimating the minimum spanning network (MSN) connecting them. The different allometric growth rates of the tubercule among island groups were significantly related to island latitude and climatic factors. On the other hand, the clustering of islands and the MSN based on male exopodite shape differences were not related to the palaeogeography of the Aegean region or to the present geographic distances of islands. These results are interpreted as evidence for non-adaptive radiation of the morphs. Resumen El isópodo terrestre Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) es una especie extensamente polimórfica distribuida por la región sur-central del piélago Egéo (Grecia), con una forma distinta en cada isla. Se trata de variaciones en la coloración, el tamaño de los tubérculos cuticulares y en la forma del primer exopodio masculino del pleopodo (carácter sexual secundario de importancia taxonómica). Estudiamos el crecimiento alométrico del tubérculo cuticular en 17 poblaciones (en individuos de ambos sexos) y la variación de la forma del primer exopodio masculino del pleopodo en 10 poblaciones según el análisis de Fourier elíptico (Elliptic Fourier Analysis) para detectar patrones de variación intraespecifica y relaciones posibles entre las formas de la especie. Además, el análisis Thin Plate Spline fue utilizado para el cálculo de la Energía de Flexión Mínima (Minimum Bending Energy) entre diversas formas del exopodio, que entonces fue utilizada para estimar la Mínima Red de Distancias (Minimum Spanning Network, MSN) que las conectaba. Detectamos una correlación significativa entre las diversas tasas de crecimiento alométrico del tubérculo entre los grupos de islas y la latitud de la isla. Por otro lado, la agrupación de las islas y la MSN, basada en las diferencias de la forma del exopodio, no fueron relacionados con la paleogeografía de la región del piélago Egéo ni con las actuales distancias geográficas de las islas. Estos resultados se interpretan como evidencia para la radiación non-adaptativa de las diversas formas de la especie. [source] Molecular Modeling and Receptor-Dependent (RD) 3D-QSAR Approach to a Set of Antituberculosis DerivativesMOLECULAR INFORMATICS, Issue 11-12 2009Fernanda, Kerly, Mesquita Pasqualoto Abstract In this study, receptor-dependent (RD) 3D-QSAR models were built for a set of thirty-seven isoniazid derivatives bound to the enoyl-acp reductase from M. tuberculosis, called InhA (PDB entry code 1zid). Ligand-receptor (L-R) molecular dynamics (MD) simulations [500,000 steps; the step size was 0.001,ps (1,fs)] were carried out at 310,K (biological assay temperature). The hypothesized active conformations resulting from a previously reported receptor-independent (IR) 4D-QSAR analysis were used as the molecular geometries of each ligand in this structure-based L-R binding research. The dependent variable is the reported MIC values against M. tuberculosis var. bovis. The independent variables (descriptors) are energy terms of a modified first-generation AMBER force field combined with a hydration shell aqueous solvation model. Genetic function approximation (GFA) formalism and partial least squares (PLS) regression were employed as the fitting functions to develop 3D-QSAR models. The bound ligand solvation energy, the sum of electrostatic and hydrogen bonding energies of the unbound ligand, the bending energy of the unbound ligand, the electrostatic intermolecular L-R energy, and the change in hydrogen bonding energy upon binding were found as important energy contributions to the binding process. The 3D-QSAR model at 310,K has good internal and external predictability and may be regarded as representative of the binding process of ligands to InhA. [source] |