Flow Rate Prediction for a Semi-permeable Membrane at Low Reynolds Number in a Circular Pipe

Transport in Porous Media - A concise and accurate prediction method is required for membrane permeability in chemical engineering and biological fields. As a preliminary study on this topic, we...     

Mechanistic investigations on the reaction between amines or amides and an alkylperoxy-lambda3-iodane

A mechanism involving the intermediate formation of an amine radical cation by single-electron transfer is proposed for the oxidation of secondary amines with alkylperoxy-lambda(3)-iodane. On the other hand, the oxidation of acetamides probably proceeds by a radical process, which involves the direct hydrogen abstraction of the methylene group alpha to the nitrogen atom.     

A novel and general synthetic pathway to strychnos indole alkaloids: total syntheses of (-)-tubifoline, (-)-dehydrotubifoline,and (-)-strychnine using palladium-catalyzed asymmetric allylic substitution

A method of palladium-catalyzed asymmetric allylic substitution for synthesizing 2-substituted cyclohexenylamine derivatives was established. Treatment of a 2-silyloxymethylcyclohexenol derivative with ortho-bromo-N-tosylaniline in the presence of Pd(2)dba(3).CHCl(3) and (S)-BINAPO in THF afforded a cyclohexenylamine derivative with 84% ee in 80% yield. The Heck reaction was carried out to produce an indolenine derivative in good yield. Using this method, we synthesized indolenine derivative 7, which was recrystallized from EtOH to give an optically pure compound. From this compound, tetracyclic ketone 13, which should be a useful intermediate for the synthesis of indole alkaloids, could be synthesized. The total syntheses of (-)-dehydrotubifoline, (-)-tubifoline, and (-)-strychnine were achieved from 13. All ring constructions for the syntheses of these natural products were achieved using a palladium catalyst.     

A new and general synthetic pathway to strychnos indole alkaloids: total syntheses of (-)-dehydrotubifoline and (-)-tubifoline by palladium-catalyzed asymmetric allylic substitution

[see reaction]. A novel procedure for the synthesis of an indole skeleton was developed. Treatment of a cyclohexenol derivative having a silyloxymethyl group at the 2-position with N-tosyl-o-bromoaniline in the presence of Pd2dba3*CHCl3 and (S)-BINAPO gave compound 6a with 84% ee in 75% yield. Compound 6a was converted into 11, which was treated with Pd(OAc)2 and Me(2)PPh in the presence of Ag2CO3 to give indoline derivative 12. From 12, we succeeded in the total syntheses of (-)-dehydrotubifoline and (-)-tubifoline.     

Influence of Density Fluctuation on DNS of Turbulent Channel Flow in the Presence of Temperature Stratification

To investigate the effect of density variation on turbulent heat transfer prediction, we perform a direct numerical simulation (DNS) of turbulent flow in a horizontal channel with varying wall temperature using a new method dealing with the effect of density variation. As a result, asymmetric profiles are observed in turbulence statistics. This tendency cannot be reproduced by the Boussinesq approximation, which is based on the constant-density formulation. A quadrant analysis of the turbulent shear stress finds that the density variation affects ejection events in the vicinity of the walls. It is also revealed that the variable viscosity and thermal conductivity change the dynamic and thermodynamic balances of the flow.     

Heat Transfer and Particle Behaviours in Dispersed Two-Phase Flow with Different Heat Conductivities for Liquid and Solid

Liquid-solid two-phase flow with heat transfer is directly simulated, to investigate the effects of the ratios of heat conductivities (solid to liquid) and bulk solid volume fraction from dense to dilute situations. The interaction between fluid and particles is solved by our original immersed solid approach on a rectangular grid system. A discrete element method with a soft-sphere collision model is applied for particle-particle and particle-wall interactions. Governing equation of temperature is time-updated with an implicit treatment for the diffusion term, which enables robust simulation with particles of very high/low ratios of heat conductivities (from 1/1000 to 1000) to the fluid. The local heat flux at the fluid-solid interface is modelled by a new flux decomposition technique, and incorporated into the implicit scheme of the temperature. The method is applied to a 2-D particulate flow in a natural convection in a square domain at a relatively low Rayleigh number. In the dense condition, for the cases with high ratios of heat conductivity, the heat transfer is promoted by strong convection, while the particles of low ratios of heat conductivity tend to hinder the development of the temperature rise in the flow field, causing a weak convection and low Nusselt number. Under a condition of relatively low solid volume fraction, fixed particles only depress the heat convection as the number of particles and heat conductivity ratio increase. For the cases with freely-moving particles, on the other hand, heat conductivity of particles has a stronger influence on the heat transfer of the system than the number of particles. The above simulation results highlight the effect of temperature distributions within the particles and liquid.