Poly(styrene sulfonic acid)–poly(vinylidene fluoride) interpolymer ion-exchange membranes. I. Preparation and characterization

Highly porous interpolymer ion-exchange membranes have been prepared from poly(styrene sulfonic acid), PSSA and poly(vinylidene fluoride) PVdF using a casting solvent of dimethylformamide and hexamethylphosphoramide. The membranes have been characterized by their water content, concentration potential, ionic conductivity, and their hydraulic permeability. An estimation of the porosity of the membranes has been made from the relative conductance of the potassium and the tetrabutylammonium ions in the film. This porosity has been compared with that derived from a consideration of the water flux through a Poiseuille-type pore.     

Velocity of sound in two-phase media

A theory is developed for calculating the velocity of sound in solid-gas and liquid-gas systems. Using mass and momentum balances, an equation is obtained which shows that the velocity of sound depends on the relative velocity between the two phases, on the ratio of densities, on the porosity, on the particle diameter, on the drag coefficient, and on the frequency of sound.

The theory can be applied only if the one phase is distributed in the other homogeneously in the form of particles, droplets or bubbles of equal size. The experimental results agree very well with the theory.

Based on Hert'z equation for the deformation of spheres, a further theory is described which enables calculation of the velocity of sound in gas-solid systems of low porosity, such as packings or porous bodies.     

Production of cellulolytic and xylanolytic enzymes during growth of anaerobic fungi from ruminant and nonruminant herbivores on different substrates

Applied Biochemistry and Biotechnology - Three anaerobic fungi, twoNeocallimastix strains isolated from a ruminant (sheep) and onePiromyces strain isolated from a nonruminant (black rhinoceros),...     

The hexaazidosilicate(IV) ion: synthesis,properties, and molecular structure

The reaction of SiCl4 with an excess of (PPN)N3 (PPN+ = [(Ph3P)2N]+) affords selectively (PPN)2[Si(N3)6] (1). Simultaneous thermal analysis (TG-DTA) shows that the hexaazidosilicate salt is remarkably stable, melting at Tonex = 214 degrees C. Melting of 1 is followed by two distinct exothermic decomposition processes at Ton = 256 and 321 degrees C, the first one involving elimination of N2 and the second one degradation of the PPN cations and evolution of Si(N3)4, N2, and some HN3. The crystal structure of 1 consists of discrete PPN+ cations and S2 symmetric [Si(N3)6]2- anions, which have a very rare, octahedral SiN6 framework and the highest nitrogen content (90%) among the hexaazidometallates reported so far. The IR, Raman, 29Si, and 14N NMR spectra of 1 in CH3CN suggest in combination with the calculated spectra the presence of intact [Si(N3)6]2--anions of S6 symmetry in solution. Geometry optimizations with various methods and basis sets show an S6 symmetric structure to be the most stable [Si(N3)6]2- isomer, the calculated bonding parameters comparing well with the experimental values.     

Decomposition of oroidin in DMSO/TFA

Oxidative cyclization of the pyrrole-imidazole alkaloids oroidin and sventrin in DMSO/TFA (1:1) yields oxazolines via nucleophilic attack of the carbonyl oxygen at the alkenyl double bond. Oxidation takes place in the benzylic position of the imidazole ring. On prolonged reaction times, the oxazoline ring is hydrolyzed yielding the corresponding ester of pyrrole-2-carboxylic acid containing a free amino group. Overall, the double bond of oroidin is dioxygenated.