Linear spaces on v points with v−2 mutually intersecting long lines

Finite linear spaces on v points with v–2 mutually intersecting long lines are completely characterized.Dedicated to Professor Giuseppe Tallini on the occasion of his 60^th birthday.Work supported by Italian M.P.I. 8nd by GNSAGA of CNR     

Iron stains on paper. Can electrophoretic removal become an effective alternative to chemical cleaning?

Abstract

Research in restoration and conservation is directed vs. more sustainable working materials, methods and technologies. Electrophoretic removal, from porous material, of undesired stains due to charged species is theoretically an interesting alternative to chemical cleaning methods, but the lack of specific and comprehensive research work leads to controversial opinions about the efficiency and the needed harmfulness for the treated objects. In this work paper, samples with artificial rust stains were subjected to electrophoretic cleaning treatments in mineral water as electrolyte. Treatments were carried out either in a bath by complete sample immersion between the distanced electrodes or by sample wetting and sandwiching between the electrodes. Evaluation of cleaning efficiency and treatment effects was based on colour change measurements (image analysis of scanned paper samples before and after the treatment and by colorimetric data via spectrophotometric measurements), investigation of morphological changes by SEM observations and folding endurance measurements.     

Adsorption of liquid mixtures on silicalite-1 zeolite: a density-bottle method

A technique that measures the effective density of a zeolite after adsorption from the liquid phase was developed to measure the absolute amounts of liquid mixtures adsorbed on zeolites without using a nonadsorbing solvent. Since the fugacities of the adsorbing components in solution can be dramatically different with or without the addition of a nonadsorbing solvent, this technique measures mixture isotherms that can be used for analyzing pervaporation through zeolite membranes. A nonideal solution, methanol/acetone, was used as an example to show that its adsorption isotherms on silicalite-1 zeolite at 294 K differ dramatically from those measured with the nonadsorbing solvent method. The methanol/acetone fugacity ratio is different for the two methods because of different concentrations in the liquid phase. Methanol preferentially adsorbs on silicalite-1 at low methanol concentrations and acetone preferentially adsorbs at high methanol concentrations. The density bottle method was used to show that n-hexane preferentially adsorbs from n-hexane/3-methylpentane liquid mixtures, and at high n-hexane concentrations, essentially no 3-methylpentane adsorbs, as has been predicted previously by simulations. A larger molecule, 2,2-dimethylbutane, adsorbed so slowly at 294 K that silicalite had only 16% of saturation coverage after 370 h, but it was saturated after 1650 h; at 423 K, saturation was obtained in less than 24 h.     

Analysis of transient permeation as a technique for determination of sorption and diffusion in supported membranes

Systematic membrane selection, process design as well as elucidation of structure–property relationships for pervaporation and vapor permeation require knowledge of sorption and diffusion properties. Direct measurement of sorption is not possible in the case of commercial membranes due to the presence of a support layer. Sorption measurements may also be difficult if the polymer is synthesized or crosslinked directly on the support and its properties are different from the bulk polymer. This work describes a technique to obtain sorption as well as diffusion parameters for supported membranes using transient permeation data. Computer simulations for transient permeation were carried out using sorption and diffusion data from the literature. It was demonstrated that the desired parameters could be estimated using data having a reasonable degree of error (±2%) by the least squares method. Alternatively, a time-lag analysis may be used instead of direct regression of the parameters by the least squares method. A general method for estimating the sorption as well as diffusion parameters using the time-lag and steady-state flux is described. Analytical solutions are derived for the various transport models, wherever possible.