A cationic rhodium(I) complex having a skewphos ligand is shown to be a highly enantioselective catalyst for asymmetric carbocyclization of 1,6-enynes with tri-substituted olefins to control quaternary stereogenic centers of spiro-rings. 相似文献
Geometric immobilization of azacrown ligand onto a fluorophore is expected to change their binding properties toward ion discrimination. An immobilized azacrown ligand 1 onto anthracene fluorophore senses Al(III), Cu(II) and Ga(III) in ethanol among the metal ions examined. In 100% aqueous solution, ligand 1 shows large CHEF effects with Al(III) and Ga(III) and large CHEQ effect with Hg(II). By comparison, non-immobilized azacrown ligand 2 showed large CHEF effects with Al(III), Ce(III), Ga(III), La(III) and Zn(II) in ethanol. 相似文献
Through the one-dimensional analysis of the diffraction of a phase grating, we calculated the optical transfer function (OTF)
of a phase grating. By a 0th-order approximation of the optical transfer function, we analyzed the feasibility of using it
as a spatial frequency filter and obtained the structure of a grating for the optimum-filtering characteristics. The OTF of
a phase grating as an optical low-pass filter is optimal when the incoming light is equally divided into three beams. The
distance of those beams must be equal to the pixel size. The theoretical development was verified through an experiment.
Received: 21 May 2001 / Revised version: 16 July 2001 / Published online: 15 October 2001 相似文献
Summary: A water‐insoluble organic 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical is solubilized in aqueous solutions of aggregates of amphiphilic block copolymers with hydrophobic dendritic pendants. The number (100–200) of DPPH molecules solubilized in an aggregate, which is evaluated from UV‐visible absorption spectra, is in agreement with that of the DPPH radicals determined from electron paramagnetic resonance (EPR) spectroscopy. The DPPH radicals are stably solubilized without decomposition in the polymer aggregates. The radicals exhibit a single‐line EPR absorption, which is narrowed by the interspin interaction, and indicates the assembly formation of DPPH radicals in polymer aggregates. These results suggest the effective utilization of the DPPH radical as a spin‐probe indicator in aqueous solutions.
When DPPH is solubilized in aqueous solutions of NaAMPS‐b‐G2(n3), the polymer solutions become purple colored, which is characteristic of the DPPH radical. 相似文献
It is studied Korovkin type approximation theorems on C(1) ([0, 1]) the space of continuously differentiable functions on the unit interval. It is proved that test functions for which
Korovkin type approximation theorems hold depending on norms of C(1) ([0, 1]). 相似文献
This paper presents the results of investigations concerning input-output systems of an electromagnetic wave in the visible and near visible spectrum for their application in structures of integrated optics. The input-output structures used in described planar optical waveguides are in a form of prism and grating couplers. The first part of the paper contains numerical analysis of grating couplers aiming at an optimization of their geometrical parameters, strictly — the depth of the grooves in the grating coupler. The second part presents the practical realization, as well as experimental tests of the planar optical waveguide with the hybrid input-output system. As the input system of the electromagnetic wave, a prism coupler was used, and in the case of the output system — a photonic structure with grating coupler was applied. The investigated planar wave guides with the input-output structures were made of a wide energy band gap semiconductor — zinc oxide (ZnO). 相似文献