Fatigue in low-strength silica optical fibres

Fatigue behaviour was investigated for low-strength silica fibres on which macroscopic flaws were forcibly introduced by abrading. Crack growth in silica glass was also examined on the CT specimen. Stable crack growth parameters, obtained from the static and dynamic fatigue tests for abraded fibres, were determined to be about 40 which is equal to that obtained from the CT specimen, indicating that the crack growth process in abraded fibres is quite the same as in the CT specimen. This leads to the conclusion that, for the optical fibre, the allowable stress condition wherein no breaks occur is given on the basis of some basic fracture mechanics parameters obtained from the CT specimen.     

Mixing and mass transfer in concentric-tube airlift fermenters: Newtonian and non-newtonian media

The mixing and mass transfer characteristics in concentric-tube airlift gas-liquid contactors intended for possible use as fermenters are discussed. Liquid velocities, circulation times, gas hold-ups, and volumetric mass transfer coefficients were measured in water and aqueous carboxy methyl cellulose solutions. Measurements were made in an inverted conical-bottom device with draft tubes of three different diameters. An increase of liquid velocities at the column axis and a corresponding decrease of volumetric mass transfer coefficients due to the introduction of draft tubes were found for water as the liquid medium. For the non-Newtonian fluids, a complicating influence of the draft tubes on liquid velocity and mass transfer, which is attributed to a combination of factors related to improvement of liquid circulation and reduction of apparent viscosity, was observed.     

Turbulent heat and mass transfer in dilute polymer solutions

A new model based on Levich's three-zone model is developed to discuss the turbulent heat and mass transfer in drag-reducing solutions. The proposed model, which has no adjustable parameters and is represented in an explicit form, provides satisfactory predictions of the maximum heat and mass transfer reduction in smooth and rough pipes. The mass transfer to a disk rotating in drag-reducing solutions is also discussed using the proposed model.     

Catalytic activity of alkaline-earth Y zeolites and concentration of bare metal ions located in the site II of faujasite structure

The concentration of the bare metal ions located in the Site II of the alkaline-earth Y zeolites was determined from the CO adsorption, and the concentration sequence was obtained as follows: SrY>CaY>MgY>BeY. This sequence corresponded well to the radius of exchanged cation. Catalytic activity of alkaline-earth Y zeolites for the disproportionation reaction of NO, further, was discussed, and activity order of per unit amount of bare Site II cation was determined as follows: BeY>MgY>CaY>SrY>BaY. This order corresponded well to the strength of the electrostatic field of alkaline-earth Y zeolites.     

Synthetic strategies of marine polycyclic ethers via intramolecular allylations: linear and convergent approaches

Strategies for the synthesis of polycyclic ethers based on intramolecular allylations are overviewed. The intramolecular condensation of allylic stannanes and aldehydes is a powerful tool for the synthesis of oxepane derivatives. The reaction is successfully applied to the iterative total synthesis of hemibrevetoxin B (2). Further, the intramolecular allylation of alpha-acetoxy ethers provides an efficient method for the convergent synthesis of polycyclic ethers. The usefulness of the latter strategy is demonstrated in the convergent total synthesis of gambierol (4).