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排序方式: 共有156条查询结果,搜索用时 15 毫秒
31.
Carmelo Sgarlata Valeria Zito Giuseppe Arena Grazia Maria Letizia Consoli Eva Galante Corrada Geraci 《Polyhedron》2009
The binding affinity for Pb2+, Cd2+ and Hg2+ of the sinapic acid–calix[4]arene hybrid 2, having four sinapyl pendants at the upper rim, has been investigated via an UV–Vis study. Compound 2 has better complexing ability than the monomeric p-phenetidine derivative 1. This highlights that the clustering of sinapyl units in a basket-like structure, dictated by the calixarene scaffold, greatly enhances the complexing properties. Ligand 2 forms complexes even with Hg2+, which is not complexed by 1 at all; the complexes formed by 2 with Pb2+ and Cd2+ are much stronger than the analogous complexes formed by 1. The UV–Vis investigation shows that the hybrid 2 markedly favors Pb2+ over Cd2+ and Hg2+. Information on the structural properties of the complex species was obtained by 1H NMR spectroscopy. NMR data show that all three metal ions are placed into the cavity consisting of the calixarene scaffold and the sinapyl pendants, though their binding affects the coordinating regions to a different extent. 相似文献
32.
Iridescent organic films consisting of quasi-parallel wire-like microstructures are grown by castings from ethanol solutions containing mixtures of aluminium-tris-hydroxyquinoline and 1,10-phenanthroline. Spectrophotometric measurements carried out in the ultraviolet-visible range indicate that the microstructured films have angular-dependent optical behaviour, which is motivated by a refractive-index modulation over dimensions that are comparable to visible-light wavelengths. According to the results of investigations carried out by means of optical microscopy, atomic force microscopy (AFM), and scanning near-field optical microscopy (SNOM), the refractive-index modulation originates from a thickness modulation and a phase separation that occurs as the aluminium-tris-hydroxyquinoline and phenanthroline co-crystallize, with the former material being arranged to form a green luminescent pattern on the top of the latter one. 相似文献
33.
The implementation of circuits with complex dynamics is a very challenging problem. In this paper we present a new chaotic circuit based on the dynamical equations introduced in IEEE Trans. Circuits Syst., I: Fundam. Theory Appl. 51, 2476-2490 (2004). This circuit has been realized by using programmable analog devices, and, in particular, field programmable analog arrays have been used to implement a two-dimensional 3x3 grid scroll chaotic attractor. The implementation of complex dynamics with low cost circuits is very appealing; moreover, the implementation of the chaotic attractor discussed in this paper is not present in the literature. The experimental results including the synchronization between two chaotic circuits show complete agreement with the simulation results reported in IEEE Trans. Circuits Syst., I: Fundam. Theory Appl. 51, 2476-2490 (2004). 相似文献
34.
A fully nonlinear model of suspension bridges parameterized by one single space coordinate is proposed to describe overall three-dimensional motions. The nonlinear equations of motion are obtained via a direct total Lagrangian formulation and the kinematics, for the deck-girder and the suspension cables, feature the finite displacements of the associated base lines and the flexural and torsional rotations of the deck cross-sections assumed rigid in their own planes. The strain-displacement relationships for the generalized strain parameters, the elongations in the cables, the deck elongation, and the three curvatures, retain the full geometric nonlinearities. The proposed nonlinear model with its full extensional-flexural-torsional coupling is employed to study the torsional divergence caused by the static part of the wind-induced forces. Two suspension bridges are considered as case studies: the Runyang bridge (main span 1,490?m) and the Hu Men bridge (main span 888?m) in China. The evaluation of the onset of the static instability and the post-critical behavior takes into account the prestressed condition of the bridge subject to dead loads. The dynamic bifurcation that occurs at the onset of flutter is also studied accounting for the prestressed equilibrium state about which the equations of motion are obtained via an updated Lagrangian formulation. Such a bifurcation is investigated in the context of the parametric nonlinear model considering the model parameters of the Runyang Suspension Bridge together with its aeroelastic derivatives. The calculated critical wind speeds for the onset of the static and dynamic bifurcations are compared with the results obtained via linear analysis and the main differences are highlighted. Parametric sensitivity studies are carried out to assess the influence of the design parameters on the instabilities associated with the bridge aeroelastic response. 相似文献
35.
Scialò Andrea Malara Giovanni Kougioumtzoglou Ioannis A. Arena Felice 《Nonlinear dynamics》2022,109(4):2281-2295
Nonlinear Dynamics - A novel statistical linearization technique is developed for determining approximately the response statistics and the power output of U-Oscillating Water Column (U-OWC) energy... 相似文献
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N. Arena Seb Cavallaro P. D'Agostino A. D'Arrigo G. Fazio G. Giardina A. Italiano R. Palamara A. Taccone 《Few-Body Systems》1991,10(4):187-193
An analysis of thed- coincidence spectra of the7Li(3He, d)4He reaction at incident energy of 5.0 MeV and at various detector angles has been carried out. The values of the spectroscopic parameters of theJ
=1+,T=06Li state at excitation energy of 5.65 MeV have been deduced. The results, considering the experimental errors, do not appear to be dependent on the geometry and are in line with the ones adopted in literature. 相似文献
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Giuseppe Arena Raffaele P. Bonomo Annalinda Contino Fabio G. Gulino Antonio Magrì Domenico Sciotto 《Journal of inclusion phenomena and macrocyclic chemistry》1997,29(3-4):347-363
A new water soluble receptor 5,11,17,23-tetrasulphonato-25,27-di(hydroxycarbonylmethoxy)-26,28-dihydroxycalix[4]arene was synthesized andcharacterized and its proton and copper(II) complexes were studied andcompared with the analogous species of the fully carboxylated ligand5,11,17,23-tetrasulphonato-25,26,27,28-tetrakis(hydroxycarbonylmethoxy)calix[4]arene. H° and S° values are crucial for understanding thepeculiar acid-base properties of the ligand. EPR spectra together with theUV-VIS spectral data reveal the coordination stereochemistry of thecopper(II) species. 相似文献