Sulle formole per la composizione di più movimenti finiti

Rendiconti del Circolo Matematico di Palermo Series 1 -     

Synthesis and characterization of sulfonated copolyethersulfones

The present article deals with the synthesis and characterization of some sulfonated copolyethersulfones. The synthetic approach differs from the post sulfonation approach traditionally reported in the literature. The synthetic procedure is based on the use of sulfonated monomers which are then reacted with previously synthesized telechelic hydoxy‐ended poly (ether sulpnone)s. Combining the MALDI‐TOF MS and ¹H NMR analyses, with SEC‐Viscometry and TGA measurements, we demonstrate a powerful tool for characterizing the chemical composition, end chains, degree of sulfonation (DS) and molecular mass distribution (MMD) of disulfonated poly(arylene ether‐sulfone) copolymers. The characterization techniques allowed to determine the exact nature of the copolymers synthesized and to reveal some interesting features about the reaction. DMA data show that the glass transition temperature of sulfonated copolymers with similar DS increase as raise their MMD. Copolymers with a DS of 10–11 mol % reach a T_g of 244–246 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3010–3023, 2010     

Kinetic Buffers

This paper proposes a new type of molecular device that is able to act as an inverse proton sponge to slowly decrease the pH inside a reaction vessel. This makes the automatic monitoring of the concentration of pH‐sensitive systems possible. The device is a composite formed of an alkyl chloride, which kinetically produces acidity, and a buffer that thermodynamically modulates the variation in pH value. Profiles of pH versus time (pH–t plots) have been generated under various experimental conditions by computer simulation, and the device has been tested by carrying out automatic spectrophotometric titrations, without using an autoburette. To underline the wide variety of possible applications, this new system has been used to realize and monitor HCl uptake by a di‐copper(II) bistren complex in a single run, in a completely automatic experiment.     

Novel carbohydrate-based bifunctional organocatalysts for nucleophilic addition to nitroolefins and imines

Glucosamine has been selected as a cheap and readily available chiral scaffold for the synthesis of a series of novel enantiomerically pure bifunctional organocatalysts bearing a tertiary amino group in proximity to a (thio)urea group. The catalytic behaviour of these compounds, both as neutral and N-protonated species, was investigated using the addition of acetylacetone to β-nitrostyrene as a model reaction. Under optimized experimental conditions, chemical yields up to 93% and enantioselectivities up to 89% were obtained. Semiempirical (AM1) computational studies allowed to find a theoretical rationale for the chemical and stereochemical behaviour of the catalyst of choice. These catalysts were also preliminarily investigated as promoters in the addition of diethyl malonate to the N-Boc imine of benzaldehyde, affording the product in up to 81% ee.     

Mechanism of smoke suppression by metal oxides in PVC

The amount of smoke suppression induced in PVC by some metal oxides was measured as a function of temperature. The amount of CO₂ evolved in the combustion was also measured simultaneously with smoke emission. Our results show that in a smoldering condition smoke occurred almost immediately, whereas CO₂ occurred at a later stage. A good correlation was found between smoke density and char yield in nitrogen, and the amount of benzene suppression, induced by metal oxides, also correlated well with the char yield. These facts are taken as evidence that crosslinking catalyzed by metal oxides is the principal mechanism of smoke inhibition and that char oxidation is responsible for the reduction of char yield.     

Simultaneous determination of seven elements (Cl, K, Ca, Br, Fe, Cu, Zn) in blood serum by PIXE

Summary Proton induced X-ray emission (PIXE) Spectra have been obtained for the blood serum of several old-age subjects by using the Van de Graaff accelerator of Catania University. The concentration levels of Cl, K, Ca, Br, Fe, Cu, Zn have been determined simultaneously within 2 min by using 5 l of blood serum. Good agreement with literature data has been found.

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Simultanbestimmung von sieben Elementen (Cl, K, Ca, Br, Fe, Cu, Zn) im Blutserum mit Hilfe von PIXE

Zusammenfassung Mit Hilfe des Van de Graaff-Beschleunigers der Univ. Catania wurden PIXE-Spektren vom Blutserum mehrerer alter Personen aufgenommen. Mit einer Probe von 5 l konnten die obigen sieben Elemente innerhalb von 2 min bestimmt werden. Die Übereinstimmung mit Literaturangaben war gut.

     

Digital self-referencing quantitative phase microscopy by wavefront folding in holographic image reconstruction

A completely numerical method, named digital self-referencing holography, is described to easily accomplish a quantitative phase microscopy for microfluidic devices by a digital holographic microscope. The approach works through an appropriate numerical manipulation of the retrieved complex wavefront. The self-referencing is obtained by folding the retrieved wavefront in the image plane. The folding operation allows us to obtain the correct phase map by subtracting from the complex region of interest a flat area outside the microfluidic channel. To demonstrate the effectiveness of the method, quantitative phase maps of bovine spermatozoa and in vitro cells are retrieved.     

Nil-automorphisms of groups with residual properties

Let G be any group and x an automorphism of G. The automorphism x is said to be nil if, for every g ∈ G, there exists n = n(g) such that [g, _n x] = 1. If n can be chosen independently of g, we say that x is n-unipotent. A nil (resp. unipotent) automorphism x could also be seen as a left Engel element (resp. left n-Engel element) in the group G〈x〉. When G is a finite dimensional vector space, groups of unipotent linear automorphisms turn out to be nilpotent, so that one might ask to what extent this result can be extended to a more general setting. In this paper we study finitely generated groups of nil or unipotent automorphisms of groups with residual properties (e.g. locally graded groups, residually finite groups, profinite groups), proving that such groups are nilpotent.