The Complexing Abilities of Diethyleneoxy-and Xylene-bridged Cryptophanes with Alkanes

Abstract

The Syn isomers (3b and 4b) of xylene-bridged cryptophane showed selective complexing abilities for 2,2-dimethylbutane, 3-methylpentane, 3,3-di-methylpentane and 3-ethylpentane among the investigated alkanes, although the Anti isomers (3a,4a,5a) did not complex with these alkanes. However, both the Anti-and Syn-isomers (2a and 2b) of the diethyleneoxy-bridged cryptophane showed selective complexing abilities for 2,2-dimethylbutane, 3,3-dimethylpentane, 2,2,3-trimethylbutane and 2,2,3,3-terramethybutane among the investigated alkanes.     

Spontaneous formation of polymer nanoparticles by good-solvent evaporation as a nonequilibrium process

In recent years, polymer nanoparticles have been investigated with great interest due to their potential applications in the fields of electronics, photonics, and biotechnology. Here, we report the spontaneous formation of polymer nanoparticles from a clear solution containing a nonvolatile poor solvent by slow evaporation of a volatile good solvent. During evaporation of the good solvent, the solution gradually turns turbid. After evaporation, polymer nanoparticles of homogeneous shape and size are dispersed in the poor solvent. Homogeneous nucleation and successive growth of polymer particles takes place during the dynamic nonequilibrium process of solvent evaporation. The size of the particles, ranging from tens of nanometers to micrometer scale, depends on both polymer concentration and the solvent mixing ratio. Because of the physical generality of the particle formation mechanism, this procedure is applicable to a wide variety of polymers with suitable combinations of solvents. Here, we also show unique features, surface structures and surface properties of polymer nanoparticles prepared by this method.     

A transient finite element analysis of natural convection around a horizontal hot cylinder

This paper presents an advanced method for a 2-dimensional analysis of transient natural convection by finite element method. The present method, based on stream function—vorticity formulation, could get rid of numerical errors and constraint of perpendicular mesh subdivision, since we excluded a finite difference approximation of vorticity on no-slip boundaries. A considerable effect of upwind weighting function was examined. The method was successfully applied to a problem of natural convection around a horizontal hot cylinder.     

Electroreflectance and Raman scattering investigation of glow-discharge amorphous Si:F:H

The electroreflectance and Raman scattering spectra of several samples of glow-discharge amorphous Si:F:H films have been investigated. We have observed for the first time modulated optical spectroscopy structure above the absorption edge for a disordered semiconductor. The energy positions of these structures, at 3.4 and 4.5 eV, correspond to peaks seen in crystalline silicon. In particular, the latter feature can be related to the degree of disorder in the material. Also we have seen for the first time in disordered silicon (except for ion-damaged, laser annealed samples) peaks in the Raman spectra intermediate between amorphous (465 cm^-1) and crystalline materials (522 cm^-1). These experimental results provide strong evidence that a-Si:F:H possesses “microcrystalline” or some other intermediate range order (i.e., an improved connectivity between the elements of the random network.)     

Effects of crown ether on hydrogenation over nickel and cobalt boride catalysts: effects in catalyst preparation and effects as additives

The nickel and cobalt boride catalysts prepared in the presence of crown ethers show different selectivities from the ordinary boride catalysts in the reduction of cycloalkene, styrene oxide, and 4-t-butylcyclohexanone.