Slip Bands and Stress Oscillations in Bars

A model is proposed that is able to describe the phenomena of strain localization and serrated deformation, peculiar to many materials, but particularly evident in mild steel. A nonlinear elastic bar is conceived like the assemblage of thin filaments, whose energy is supposed to be a nonconvex function of the relative displacement of each filament's extremities. The model explains the onset of elastic, plastic and strain-hardening phases in the bar, interpreting the formation of slip bands and stress oscillations.     

Applications of homogenization techniques to the electrical conduction in biological tissues

We study a family of problems set in a finely mixed periodic medium, modelling electrical conduction in biological tissues. We prove a unified derivation of these different schemes from the Maxwell equations in the quasi-stationary approximation and we investigate the behaviour of the corresponding macroscopic models. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies on the synthesis of heterocyclic compounds. XIII. The synthesis of macrocyclic tetraesters from 1,2-cyclohexane- and 2,3-butanediols

A new series of macrocyclic compounds containing 1,2-cyclohexanediols and 2,3-butandiol sub-unit have been prepared treating the stannolanic and stibolanic derivatives with diacyl chlorides. The structures of the compounds prepared have been determined by elemental analysis and spectroscopic data.     

Cathodically deposited polypyridine films: A novel electroactive polyconjugated polymer

Poly-2,5- and poly-2,6-pyridine coatings have been produced on glassy-carbon electrodes by nickelcatalysed reduction of the corresponding dibromopyridine in acetonitrile. Poly-2,5-pyridine films display two reversible cathodic cycles, one of which is due to nickel ions coordinated to pyridine moieties and the other to the polymeric backbone. Both reductions lead to the polymer changing from the insulating to the conductive state. Conversely, Poly-2,6-pyridine films are not reversibly electroactive and the differences are discussed in terms of conjugation along the polymeric chain.     

Macrocyclic polyether-diester compounds as phase-transfer catalysts

Three new macrocyclic polyether-diester have been prepared. The catalytic activity of these compounds has been tested in the Br/I exchange reactions of octyl bromide with different ionic diameter cations.     

Heat capacities of aqueous mixed electrolyte solutions at high temperatures. Application of the Pitzer equations to the mixed system K−Na−Cl−SO4

Specific heats at constant pressure for the mixed system K/Na/Cl/SO₄ in H₂O have been obtained from heat content measurements by means of a drop calorimeter between 60 and 220°C over the salt concentration range 0.5–5m, with ionic strengths up to 7.5. Measurements have also been made on aqueous K₂SO₄ solutions in the same temperature range between 0.3 and 1.6m. The heat capacities of the quaternary system were represented using the semiempirical Pitzer equations neglecting the mixed interaction terms as a first approximation. A comparison of experimental with calculated data shows that the ability of this method to describe the system is satisfactory even at rather high concentrations, but only for solutions of low sulphate ion content.     

Cleavable Binary Dyads: Simplifying Data Extraction and Increasing Storage Density in Digital Polymers

Digital polymers are uniform macromolecules that store monomer‐based binary sequences. Molecularly stored information is usually extracted from the polymer by a tandem mass spectrometry (MS/MS) measurement, in which the coded chains are fragmented to reveal each bit (i.e. basic coded monomer unit) of the sequence. Here, we show that data‐extraction can be greatly simplified by favoring the formation of MS/MS fragments containing two bits instead of one. In order to do so, digital poly(alkoxyamine phosphodiester)s, containing binary dyads in each repeat unit, were prepared by an orthogonal solid‐phase approach involving successive phosphoramidite and radical‐radical coupling steps. Three different sets of monomers were considered to build these polymers. In all cases, four coded building blocks—two hydroxy‐nitroxides and two phosphoramidite monomers—were required to build the dyads. Among the three studied monomer sets, one combination allowed synthesis of uniform sequence‐coded polymers. The resulting polymers led to clear dyad‐containing fragments in MS/MS and could therefore be efficiently decoded. Additionally, an algorithm was created to detect specific dyad fragments, thus enabling automated sequencing.     

Global existence of a classical solution for a large class of free boundary problems in one space dimension

We prove global classical solvability and a uniqueness theorem for a wide class of one dimensional free boundary problems in which the evolution of the free boundarys(t) is controlled by the derivatives up to the second order ofu (u together withs(t) is an unknown of our problem) and by a functional ofs(t) itself. In the Introduction it is showed the physical background from which such problems arise.Work partially supported by the Italian M.U.R.S.T. National Project Problemi non lineari...