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91.
92.
J. R. Barber 《Journal of Elasticity》1991,26(1):75-86
The classical formulation of the homogeneous problem of a curved bar loaded only by and end force involves the assumption of an appropriate stress function with four arbitrary constants and the determination of these constants from the boundary conditions. Since there are five boundary conditions, four on the curved edge and one at the end, the solution is only possible because the coefficient matrix of the resulting algebraic equations is singular. This in turn means that certain inhomogeneous problems in which the curved edges are loaded by sinusoidally varying tractions cannot be solved using apparently appropriate stress functions.Additional stress functions which resolve this difficulty are introduced and an example problem is solved, which exhibits qualitatively different behavior from that in more general cases of loading. The problem is then reconsidered as a limiting case of sinusoidal loading of arbitrary wavelength. It is shown that the solution of the latter problem appears to become unbounded as the special case is approached, but that when the end conditions have been correctly satisfied by superposing an appropriate multiple of the end-loaded solution, the limit can be approached regularly and the correct special solution is recovered. The limiting process reveals a general procedure for determining the additional stress functions required for the special case.Similar relationships between homogeneous and inhomogeneous solutions for other common geometries are discussed. 相似文献
93.
Muhammad Adnan Asghar Jing Zhang Shiguo Han Zhihua Sun Chengmin Ji Aurang Zeb Junhua Luo 《中国化学快报》2018,29(2):285-288
Quadratic nonlinear optical properties of the picrate-based molecular crystal have been switched using the order-disorder phase transition, which opens up a potential way to design stimuli-responsive materials. 相似文献
94.
95.
Barberá J Gimeno N Monreal L Piñol R Ros MB Serrano JL 《Journal of the American Chemical Society》2004,126(23):7190-7191
The synthesis and characterization of reactive banana-shaped compounds have been carried out, and their ability to be photopolymerized in their SmCP mesophase has been assessed. The presence of a SmCP liquid crystalline phase in these compounds has been confirmed by X-ray studies. The polymerization of these molecules has been demonstrated by calorimetric techniques as well as by the preparation and characterization of SmCP-ordered free films that are mechanically stable at room temperature. Furthermore, polymerized films exhibit second harmonic generation activity at room temperature in the absence of an electric field. 相似文献
96.
Martín-Rapún R Marcos M Omenat A Barberá J Romero P Serrano JL 《Journal of the American Chemical Society》2005,127(20):7397-7403
The synthesis and characterization of two families of ionic liquid crystal dendrimers consisting of the ammonium salts of the commercially available poly(amidoamine) (G = 0-5) and poly(propylene imine) (G = 1-5) dendrimers and three long-chain carboxylic acids are reported. The liquid crystalline behavior was investigated by means of differential scanning calorimetry, polarizing light optical microscopy, and X-ray diffractometry. The thermal stability of the ionic materials was further studied by NMR. Most of the dendrimers show lamellar mesomorphism, and two of them exhibit columnar mesomorphism. On the basis of the experimental results, we propose models both at the molecular level and in the mesophase for all the materials. 相似文献
97.
Barber M Bell D Morris M Tetler L Woods M Bycroft BW Monaghan JJ Morden WE Green BN 《Talanta》1988,35(8):605-611
The characterization of components within actinomycin complexes may often be complicated by the lack of material and standards of known actinomycins. Mass spectrometry-mass spectrometry can be employed both as a separatory device and as a means of structural analysis. This technique has been applied to an actinomycin complex obtained from a previously unidentified Streptomyces strain. The method involved initial work on a known material, in this case actinomycin D, and application to the unknown material. Three major components within the unknown complex were characterized as actinomycins D, F(8), and F(9). 相似文献
98.
Ll Serra F. Garcias N. Barberán M. Barranco J. Navarro A. Rubio 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,19(4):89-91
We have calculated the static polarizability and mean excitation energy of metal clusters submitted toq-andL-dependent external fields ofj L (qr)Y L0(Ω) type. Use has been made of an Extended Random-Phase Approximation which includes exchange and correlation effects within a local model, and of the spherical jellium model to describe the neutralizing positive background. 相似文献
99.
Michael Barber David J. Bell Michael Morris Lee W. Tetler Michael D. Woods John J. Monaghan William E. Morden 《Journal of mass spectrometry : JMS》1989,24(7):504-510
The mass spectra of biological molecules, whose molecular mass exceeds 10 kDa, invariably contain multiply charged ions. For example, a survey scan of a small protein will produce singly, doubly and triply protonated molecules, the intensity of the doubly charged species often being greater than that of the singly charged entity. Although the spectra resulting from doubly charged peptides have not previously been studied, collisional activation of such doubly charged species may result in significant additional information pertaining to molecular structure. The techniques employed to study ions originating from multiply charged species were linked scanning of constant B/E and tandem mass spectrometry, namely low collision energy spectra acquired on a BEQQ hybrid instrument. The methodology was applied to model compounds whose tandem mass spectrometry characteristics are well known, e.g. gramicidin S and angiotensin I. The results for the product ions of the [M + 2H]2+ species of the models were obtained which highlight the methodology required for high-mass materials. 相似文献
100.