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81.
Two acetylene polymers containing cyanobiphenyl-based mesogens,poly { 10-[ ((4'- cyano-4-biphenylyl ) oxy ) carbonyl] - 1 -decyne } (PA8CN ), which has a relativelyfiexible polyalkyne backbone, and poly {[4-(((12-((4'-cyano-4-biphenylyl)oxy)dodecyl)oxy)carbonyl) phenyl]-acetylene} (PB12CN), which has a fairly rigid poly (phenylacetylene )backbone, were synthesized using respectively WCl_6 and [Rh(nbd)Cl]_2 as the catalysts.PA8CN exhibits enantiotropic interdigitated smectic A phase (S_(Ad)) over a temperaturerange as wide as ca. 100℃, whereas PB12CN is non-mesomorphic, demonstrating thatthe backbone rigidity plays an important role in determining the liquid crystallinity of thepolyacetylenes. 相似文献
82.
83.
Chaowei Yuan Wen Cui Yanjuan Sun Jiadong Wang Ruimin Chen Jin Zhang Yuxin Zhang Fan Dong 《中国化学快报》2020,31(3):751-754
It is of a great challenge to develop semiconductor photocatalysts with potential possibilities to simultaneously enhance photocatalytic efficiency and inhibit generation of toxic intermediates.In this study,we developed a facile method to induce the La doping and cationic vacancie(V(Zn))on ZnO for the highly efficient complete NO oxidation.The photocatalytic NO removal efficiency increases from 36.2%to 53,6%.Most importantly,a significant suppressed NO2 production also has been realized.According to the DFT calculations,ESR spectra and in situ FTIR spectra,the introduction of La^3+induce the redistribution of charge carriers in La-ZnO,which promote the production of·O2^- and lead to the formation of V(Zn)for the formation of·OH,contributing to the complete oxidation of NO to nitrate.Besides,the conversion pathway of photocatalytic NO oxidation has been elaborated,This work paves a new way to simultaneously realize the photocatalytic pollutants removal and the inhibition of toxic intermediates generation for efficient and safe air purification. 相似文献
84.
《Tetrahedron: Asymmetry》2005,16(19):3241-3255
Central intermediate 5 for the taxoid diterpene framework, prepared by the aldol–annulation sequence, permitted the construction of A-secotaxane frameworks incorporating differentiatable olefin and oxygen functionalities suitable for further elaboration. The key BC-subunits 9 and 8 have proven amenable to efficient conversion into both oxa-bridged 7 and its central eight-membered B-ring analogue 6, providing two potential precursors for taxoid construction. Although their further elaboration into 4 was not progressed at this stage, 6 and 7 are potentially useful synthetic intermediates. Extensive structural studies that included 800 MHz 1H (200 MHz 13C) NMR as well as X-ray crystallographic analyses of 7, 17, and 20 have contributed to the unambiguous elucidation of all the complex structures synthesized. 相似文献
85.
This paper focus on the event-triggered sliding mode controller design for discrete-time switched genetic regulatory networks (GRNs) with persistent dwell time (PDT) switching. Firstly, the observation error dynamics of switched GRNs with PDT is constructed in the light of event-triggered sliding mode control (SMC) scheme. Next, sufficient conditions are derived to ensure the exponential stability of the augmented plant. Moreover, an event-triggered SMC law is synthesized to impel the system trajectories onto the sliding surface in a finite time. Finally, a verification example is provided to illustrate the effectiveness and potential of the proposed method. 相似文献
86.
Lijun Zhang Shanjia Xu 《International Journal of Infrared and Millimeter Waves》1996,17(10):1735-1747
The finite element method is combined with the mode-matching method and the multi-mode network method to analyze the scattering and radiation characteristics of a class of planar dielectric waveguide discontinuities. Unlike the conventional method to treat the radiation as a source-field problem, in the present approach, the dispersion characteristics of dielectric guided-wave structures are calculated first, and then the radiation problem is transferred to the propagation problem of a series of surface-waves and space waves from the viewpoint of scattering, thus the analysis is tremendously simplified. 相似文献
87.
Hongwei Liu Xiangdong Liu KeXue Yuan KeSong Hu Yutau Chen 《International Journal of Infrared and Millimeter Waves》1993,14(8):1693-1699
A five-channel grating spectrometer for use in millimeter wave band (25100GHz) is described with its design theory of optical path, and measured results of insertion loss and resolving power. 相似文献
88.
89.
《The Journal of chemical thermodynamics》2006,38(1):20-33
The apparent molar volumes of l-alanine, dl-serine, dl-threonine, l-histidine, glycine, and glycylglycine in water and in the aqueous solutions of NaCl and DMSO with various concentrations at T = 298.15 K have been measured by the precise vibrating-tube digital densimeter. The calculated partial molar volumes at infinite dilution have been used to obtain corresponding transfer volumes from water to various solutions. The experimental results show that the standard partial molar volumes of the above amino acids and peptide at the dilute DMSO aqueous solutions are very close to those in water. However, the volumes show several types of variations with the increase of the concentrations of DMSO due to different types of side chain of amino acids, which should be discussed specifically. The NaCl changes considerably the infinite dilution standard partial molar volumes of the above amino acids and peptide in the aqueous solutions. The infinite dilution standard partial molar volumes of the each amino acids and peptide increase with the concentrations of NaCl. The experimental results have been rationalized by a cosphere overlap model. 相似文献
90.