Nonlinear cellular convection and heat transport in a porous medium

Nonlinear steady cellular convection in a fluid-saturated porous medium is investigated using the technique of spectral analysis. The effect of permeability is shown to contract the cell and to damp the convection process. The influence of Prandtl number, though small, is seen only in the fourth order term. The cross-interactions of the higher modes caused by nonlinear effects are considered through the modal Rayleigh number R . The possibility of the existence of a steady solution with two self-excited modes in certain regions is predicted. A detailed discussion of the heat transport is made. The theoretical value of the Nusselt number is found to be in good agreement with the experimental results. The similarities and qualitative differences between the present analysis and that of the power integral technique are brought out.     

Stoichiometry of the reaction between iron(II) and chromium(VI)

The suitability of potassium dichromate as a standard oxidant has been examined by comparing direct oxidation of iron(II) solutions with alternative back-titration procedures.     

Studies on the extraction of vanadium (IV) in the presence of some anions and neutral oxygen donors

Extraction of vanadium (IV) in the presence of perchlorate, nitrate, halides, and thiocyanate and neutral oxygen donors liken-butanol, TBP and antipyrine into various solvents is studied. Composition of the extracting species and the stability constants are determined. The effectiveness of the three neutral oxygen donors studied in the extraction of vanadium (IV)-anion systems is found to follow the order: antipyrine > TBP >n-butanol.     

Terpenoids—XXV Structure of saussurea lactone

Saussurea lactone is identical with the product of pyrolysis of dihydrocostunolide. On cyclisation in the presence of p-nitrobenzoic acid followed by hydrogenation it gives santanolide C. Hence structure (V) is assigned to saussurea lactone.     

Absorption and laser excited fluorescence of Ho3+:LaF3

Pramana - The absorption and fluorescence spectra of Ho3+:LaF3, in the wavelength region from 4000 Å to 7500 Å have been reinvestigated incorporating polarization features, for the first...     

Simple synthesis of 2-acetyl-5,8-dimethoxy-3,4-dihydronaphthalene,a key intermediate for the synthesis of optically active anthracycliones

2-Acetyl-5,8-dimethoxy-3,4-dihydronaphthalene is synthesised easily·starting from 2-acetyl-5,8-dimethoxytetralone.