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  • 1
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    Green synthesis and crystal structure of 3-(benzothiazol-2-yl)thiophene (2017)
    International Union of Crystallography
    Details
    Publication Date: 2017-10-13
    Description: The title compound, C11H7NS2, was prepared in high yield (87%) using a solvent-free microwave-assisted synthesis. The structure shows whole-molecule disorder with occupancies for two orientations (A and B) of 0.4884 (10) and 0.5116 (10), respectively. The thiophene and benzothiazole rings are almost planar and make dihedral angles of 10.02 (18) and 12.54 (19)° for orientations A and B, respectively. Slipped π–π stacking between the aromatic rings, together with C—H...π, C—H...S and C—H...N interactions, result in a herringbone motif in the crystal packing.
    Electronic ISSN: 2056-9890
    Topics: Chemistry and Pharmacology , Geosciences
    Published by International Union of Crystallography
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  • 2
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    Synthesis, crystal structure and Hirshfeld surface analysis of diethyl 2,6-dimethyl-4-(thiophen-3-yl)-1,4-dihydropyridine-3,5-dicarboxylate (2019)
    International Union of Crystallography
    Details
    Publication Date: 2019-11-15
    Description: In the title compound, C17H21NO4S, the 1,4-dihydropyridine ring has an envelope conformation with the Csp 3 atom at the flap. The thiophene ring is nearly perpendicular to the best plane through the 1,4-dihydropyridine ring, the dihedral angle being 82.19 (13)°. In the crystal, chains running along the b-axis direction are formed through N—H...O interactions between the 1,4-dihydropyridine N atom and one of the O atoms of the ester groups. Neighbouring chains are linked by C—H...O and C—H...π interactions. A Hirshfeld surface analysis shows that the most prominent contributuion to the surface contacts are H...H contacts (55.1%).
    Electronic ISSN: 2056-9890
    Topics: Chemistry and Pharmacology , Geosciences
    Published by International Union of Crystallography
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  • 3
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    Crystal structure of two N′-(1-phenylbenzylidene)-2-(thiophen-3-yl)acetohydrazides (2019)
    International Union of Crystallography
    Details
    Publication Date: 2019-07-02
    Description: The synthesis, spectroscopic data, crystal and molecular structures of two N′-(1-phenylbenzylidene)-2-(thiophen-3-yl)acetohydrazides, namely N′-[1-(4-hydroxyphenyl)benzylidene]-2-(thiophen-3-yl)acetohydrazide, C13H10N2O2S, (3a), and N′-[1-(4-methoxyphenyl)benzylidene]-2-(thiophen-3-yl)acetohydrazide, C14H14N2O2S, (3b), are described. Both compounds differ in the substituent at the para position of the phenyl ring: –OH for (3a) and –OCH3 for (3b). In (3a), the thiophene ring is disordered over two orientations with occupancies of 0.762 (3) and 0.238 (3). The configuration about the C=N bond is E. The thiophene and phenyl rings are inclined by 84.0 (3) and 87.0 (9)° for the major- and minor-occupancy disorder components in (3a), and by 85.89 (12)° in (3b). Although these dihedral angles are similar, the conformation of the linker between the two rings is different [the C—C—C—N torsion angle is −ac for (3a) and −sc for (3b), while the C6—C7—N9—N10 torsion angle is +ap for (3a) and −sp for (3b)]. A common feature in the crystal packing of (3a) and (3b) is the presence of N—H...O hydrogen bonds, resulting in the formation of chains of molecules running along the b-axis direction in the case of (3a), or inversion dimers for (3b). The most prominent contributions to the surface contacts are those in which H atoms are involved, as confirmed by an analysis of the Hirshfeld surface.
    Electronic ISSN: 2056-9890
    Topics: Chemistry and Pharmacology , Geosciences
    Published by International Union of Crystallography
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  • 4
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    Crystal structure of (E)-N'-[1-(4-aminophenyl)ethylidene]-2-hydroxy-5-iodobenzohydrazide methanol monosolvate (2018)
    International Union of Crystallography
    Details
    Publication Date: 2018-06-08
    Description: In the title compound, C15H14IN3O2·CH3OH, two aromatic rings are linked by an N-substituted hydrazide function. The dihedral angle between the aromatic rings is 10.53 (8)°. The stereochemistry about the imine function is E. The methanol molecule forms an O—H...O hydrogen bond to the hydrazide O atom. In the crystal, chains of molecules running along the c-axis direction are formed by O—H...O hydrogen bonds. Adjacent chains are linked through N—H...O hydrogen bonds and π–π stacking interactions. The intermolecular interactions in the crystal packing were investigated using Hirshfeld surface analysis, which indicated that the most significant contacts are H...H (38.2%), followed by C...H/H...C (20.6%), O...H/H...O (11.1%) and I...H/H...I (9.7%).
    Electronic ISSN: 2056-9890
    Topics: Chemistry and Pharmacology , Geosciences
    Published by International Union of Crystallography
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  • 5
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    Synthesis, structure and in vitro cytotoxicity testing of some 1,3,4-oxadiazoline derivatives from 2-hydroxy-5-iodobenzoic acid (2018)
    International Union of Crystallography
    Details
    Publication Date: 2018-06-18
    Description: The syntheses of nine new 5-iodosalicylic acid-based 1,3,4-oxadiazoline derivatives starting from methyl salicylate are described. These compounds are 2-[4-acetyl-5-methyl-5-(3-nitrophenyl)-4,5-dihydro-1,3,4-oxadiazol-2-yl]-4-iodophenyl acetate (6a), 2-[4-acetyl-5-methyl-5-(4-nitrophenyl)-4,5-dihydro-1,3,4-oxadiazol-2-yl]-4-iodophenyl acetate (6b), 2-(4-acetyl-5-methyl-5-phenyl-4,5-dihydro-1,3,4-oxadiazol-2-yl)-4-iodophenyl acetate, C19H17IN2O4 (6c), 2-[4-acetyl-5-(4-fluorophenyl)-5-methyl-4,5-dihydro-1,3,4-oxadiazol-2-yl]-4-iodophenyl acetate, C19H16FIN2O4 (6d), 2-[4-acetyl-5-(4-chlorophenyl)-5-methyl-4,5-dihydro-1,3,4-oxadiazol-2-yl]-4-iodophenyl acetate, C19H16ClIN2O4 (6e), 2-[4-acetyl-5-(3-bromophenyl)-5-methyl-4,5-dihydro-1,3,4-oxadiazol-2-yl]-4-iodophenyl acetate (6f), 2-[4-acetyl-5-(4-bromophenyl)-5-methyl-4,5-dihydro-1,3,4-oxadiazol-2-yl]-4-iodophenyl acetate (6g), 2-[4-acetyl-5-methyl-5-(4-methylphenyl)-4,5-dihydro-1,3,4-oxadiazol-2-yl]-4-iodophenyl acetate (6h) and 2-[5-(4-acetamidophenyl)-4-acetyl-5-methyl-4,5-dihydro-1,3,4-oxadiazol-2-yl]-4-iodophenyl acetate (6i). The compounds were characterized by mass, 1H NMR and 13C NMR spectroscopies. Single-crystal X-ray diffraction studies were also carried out for 6c, 6d and 6e. Compounds 6c and 6d are isomorphous, with the 1,3,4-oxadiazoline ring having an envelope conformation, where the disubstituted C atom is the flap. The packing is determined by C—H...O, C—H...π and I...π interactions. For 6e, the 1,3,4-oxadiazoline ring is almost planar. In the packing, Cl...π interactions are observed, while the I atom is not involved in short interactions. Compounds 6d, 6e, 6f and 6h show good inhibiting abilities on the human cancer cell lines KB and Hep-G2, with IC50 values of 0.9–4.5 µM.
    Electronic ISSN: 2053-2296
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by International Union of Crystallography
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  • 6
    Electronic Resource
    Electronic Resource
    Multilayer beams: A geometrically exact formulation (1996)
    Springer
    Journal of nonlinear science 6 (1996), S. 239-270 
    Details
    ISSN: 1432-1467
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Summary We review and extend our recent work on a new theory of multilayer structures, with particular emphasis on sandwich beams/1-D plates. Both the formulation of the equations of motion in the general dynamic case and the computational formulation of the resulting nonlinear equations of equilibrium in the static case based on a Galerkin projection are presented. Finite rotations of the layer cross sections are allowed, with shear deformation accounted for in each layer. There is no restriction on the layer thickness; the number of layers can vary between one and three. The deformed profile of a beam cross section is continuous, piecewise linear, with a motion in 2-D space identical to that of a planar multibody system that consists of three rigid links connected by hinges. With the dynamics of this multi (rigid/flexible) body being referred directly to an inertial frame, the equations of motion are derived via the balance of (1) the rate of kinetic energy and the power of resultant contact (internal) forces/couples, and (2) the power of assigned (external) forces/couples. The present formulation offers a general method for analyzing the dynamic response of flexible multilayer structures undergoing large deformation and large overall motion. With the layersnot required to have equal length, the formulation permits the analysis of an important class of multilayer structures with ply drop-off. For sandwich structures, an approximated theory with infinitesimal relative outer-layer rotations superimposed onto finite core-layer rotation is deduced from the general nonlinear equations in a consistent manner. The classical linear theory of sandwich beams/1-D plates is recovered upon a consistent linearization. Using finite element basis functions in the Galerkin projection, we provide extensive numerical examples to verify the theoretical formulation and to illustrate its versatility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02439311
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  • 7
    Electronic Resource
    Electronic Resource
    On Similarity to Contraction Semigroups in Hilbert Space (1998)
    Springer
    Semigroup forum 56 (1998), S. 197-204 
    Details
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: 0 -semigroup in Hilbert space, then T(t) is similar to a contraction semigroup. Analogously, if T is a power-bounded quasi-compact operator, then T is similar to a contraction. This latter fact is a simultaneous generalization of well known results of Sz.-Nagy and Rota. Some characterizations of bounded quasi-compact semigroups and power-bounded quasi-compact operators are also given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005941
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  • 8
    Electronic Resource
    Electronic Resource
    On a highly robust spurious-mode filtering method for uniformly reduced-integrated shell elements (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 34 (1992), S. 209-220 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In structural elements that allow shear deformation, uniformly reduced integration is used to avoid shear and membrane locking. The spurious modes of an underintegrated stiffness matrix can be filtered using perturbation methods. Although finite elements with perturbed stiffness show very good results, the displacements still conceal a component of spurious modes, albeit with very small magnitude depending on the perturbation factor. To desensitize the numerical results completely from the perturbation factor, a projection of the applied force is proposed to complement the perturbation of the stiffness such that spurious modes are not excited, thus providing robustness to the filtering of spurious modes. The proposed methodology is general in nature, but is applied in this paper to a 9-node shell element with uniformly reduced integration as an illustration. The perturbation of the stiffness matrix and the projection of the force vector are performed at the element level, avoiding expensive local-global transformations. As a consequence of the force projection, the perturbation factor for the stiffness can be arbitrarily small, and the element yields accurate results for a wide range of shell thickness.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620340113
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  • 9
    Electronic Resource
    Electronic Resource
    New predictor/corrector algorithms with improved energy balance for a recent formulation of dynamic vehicle/structure interaction (1991)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 32 (1991), S. 223-253 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new class of predictor/corrector algorithms is proposed to solve the complex system of differential equations that arises from a Galerkin spatial discretization of the equations of motion in a recent formulation of dynamic vehicle/structure interaction. The applicability of the concept of a building-block vehicle/structure interaction model developed in our previous work - where the vehicle nominal motion is not prescribed a priori, but is part of the unknown motion of the system - is demonstrated through the construction of a simple vehicle model. In the new algorithms, the presence of the accelerations of the vehicle component is eliminated in the predictor structural equations, making these equations different from the corrector structural equations. The special treatment of the predicted axial motion that provides an artificial damping to eliminate unstable oscillations in the numerical results as proposed in the old algorithms is avoided. Accurate results from numerical simulations using the new algorithms are obtained, and there are no unstable oscillations that were observed in some other predictor/corrector schemes. The system energy balance is also better preserved compared with the old algorithms.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620320202
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  • 10
    Electronic Resource
    Electronic Resource
    Efficient evaluation of the flexibility of tapered I-beams accounting for shear deformations (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 553-566 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The principle of complementary virtual work is used to evaluate numerically the flexibility matrix of tapered I-beams accounting for shear deformations. Equilibrium considerations of the top and bottom fibres reveal that the shear stress is not equal to zero at these locations. To correct for this non-vanishing shear, a statically admissible shear stress field is considered by assuming a parabolic distribution of shear stress which takes non-zero values at the top and bottom fibres such that the global equilibrium is satisfied within the assumed stress profile. The flexibility matrices of the proposed tapered I-beam finite element with different slopes are generated using numerical integration based on Gauss quadrature. The results are compared to full-blown shell finite element models, and stepped beam models constituted by a series of uniform beam elements, to illustrate the effectiveness of the proposed method.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330306
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