Porosity enhancement by the utilization of screening patterns in electro-perforated paper webs

In this work, a technique to enhance the porosity of electro-perforated paper webs using screening matrices is described. The proposed approach relies on the confining effect that acts on a train of sparks when forced to pass through a small hole pierced through a ceramic substrate located in-between two needle-like electrodes. It is shown how the maximum porosity level achievable by the electro-perforation process depends on the drag distance parameter. Since the proposed method is aimed at reducing the latter, an eventual enhancement of the number of perforations per unit area can be obtained. The method has been experimentally tested. It is worth mentioning the suitability of the matrix-aided paper perforation process for its use in industrial environments.     

Computing with words in decision making: foundations, trends and prospects

Computing with Words (CW) methodology has been used in several different environments to narrow the differences between human reasoning and computing. As Decision Making is a typical human mental process, it seems natural to apply the CW methodology in order to create and enrich decision models in which the information that is provided and manipulated has a qualitative nature. In this paper we make a review of the developments of CW in decision making. We begin with an overview of the CW methodology and we explore different linguistic computational models that have been applied to the decision making field. Then we present an historical perspective of CW in decision making by examining the pioneer papers in the field along with its most recent applications. Finally, some current trends, open questions and prospects in the topic are pointed out.     

Conformation and stability of the hydrogen-bonded complex 6-oxabicyclo

The hydrogen-bonded complex between 6-oxabicyclo[3.1.0]hexane and hydrogen chloride was investigated by microwave spectroscopy in a supersonic jet. A dual flow pulsed valve was used to preclude chemical reaction between the monomers. Only the equatorial conformer was observed and the spectra of three isotopomers, (C5H8O, H35Cl), (C5H8O, H37Cl) and (C5H8O, D35Cl), were measured. The derived structure of the complex has Cs symmetry with the hydrogen chloride pointing to the domain of the equatorial lone pair of electrons at the oxygen atom. The three atoms involved in the hydrogen bond adopt a bent arrangement with a O...H distance of 1.77(4) A, a (O...H-Cl) angle of 115(4)degrees, and a deviation of 15.4(14)degrees of the hydrogen bond from collinearity. In agreement with the experimental results, ab initio calculations predict the equatorial form to be the most stable one.     

The surfactant-sensitized analytical reaction of niobium with 8-hydroxyquinoline-5-sulphonic acid

Cationic surfactants, such as cetylpyridinium bromide (CPB), sensitize the colour reaction of Nb(V) with 8-hydroxyquinoline-5-sulphonic acid (H(2)L). The formation of a ternary complex of stoichiometry 1:3:3 (Nb-L-CPB) is responsible for the observed enhancement in absorptivity and the quenching in the fluorescence of the Nb-L chelate, when a surfactant is present. The ternary complex exhibits maximum absorption at 383 nm ( = 1.46 +/- 0.01 x 10(4) l.mole(-1).cm(-1)) at pH 5.7, and Beer's law is obeyed up to 6-mug ml Nb concentration. Conditional formation constants of the niobium chelate in the presence and absence of CPB have been determined. On the basis of a detailed spectrophotometric and fluorimetric study the nature of the chromophoric reagent-surfactant interaction and the peculiar features of the sensitization by CPB are discussed.     

Affinity chromatography study of the interaction of ribonucleotides with bovine pancreatic ribonuclease covalently bound to Sepharose 4B

The preparation of immobilized bovine pancreatic ribonuclease by covalent attachment to Sepharose 4B, with and without a spacer arm, is described. The coupling reaction was carried out at two different pH values, 8.5 and 10.5, and the different kinetic properties shown by the resulting preparations probably reflect the influence of the particular amino acid side-chains involved in the covalent coupling of the enzyme to the insoluble matrix. The strength of binding of mononucleotides, at 4 degrees C, as deduced from the salt concentration at which they are eluted from an immobilized RNAase column, follows the order 5'-GMP greater than 5'-AMP greater than 3'-UMP greater than 3'-CMP. When binary mixtures of a 3'-pyrimidine nucleotide and a 5'-purine nucleotide are chromatographed jointly, a co-operative effect is found and the elution of either or both ligands is retarded. This behaviour can be explained in terms of the preferential binding of each kind of nucleotide to different sub-sites in the enzyme. The stoichiometry and association constant for 3'-CMP and 5'-AMP at pH 7.0 were also determined.     

Semiempirical calculation of the surface dipole barrier in metals

The surface dipole barrier D of metals is calculated from experimental work functions and theoretical bulk chemical potentials obtained by the Augmented-Spherical-Waves method of Williams et al. Two independent linear relations between D and the electron density at the boundary of Wigner-Seitz cells are found for transition and non transition metals. An explanation for this difference is offered.     

Determination of the degree of acetylation of chitin and chitosan by thermal analysis

Several methods for the rapid determination of the degree of acetylation of chitin and related polymers have been evaluated, including the use of the infrared and the mass spectra. Chitin and chitosan have characteristic degradation temperatures and it is possible to determine the acetylation degree by the use of empirical correlations based on the weight losses associated with the main decomposition peaks.     

Tandem radical addition and cyclization of epsilon-substituted delta-yne ketimines

The first one-step conversions of ketimines I into cyclized allylamine derivatives of types II and III are reported.