A practical entry to C18-constrained-E-ring analogues of methyllycaconitine (MLA): a concise new stereoselective approach to 8-oxa-decahydroisoquinolines accompanied by a simple microwaves-assisted synthesis of the succinimidobenzoate appendage of MLA

A Mannich-type intramolecular cyclization afforded access to a 8-oxa-decahydroisoquinoline heterocyclic system. Good stereoselectivity was observed. A promising microwave-assisted synthesis of the methylsuccinimidobenzoate moiety of methyllycaconitine has also been carried out.     

Relation between configurational entropy and relaxation dynamics of glass-forming systems under volume and temperature reduction

The structural relaxation dynamics of two molecular glass-forming systems have been analyzed by means of dielectric spectroscopy, under cooling and compression conditions. The relation of the dynamic slowing down with the reduction of the configurational entropy, S_C, as predicted by Adam and Gibbs (AG), was also investigated. As S_C is not directly accessible by experiments, it was estimated, following a common procedure in literature, from the excess entropy S_exc of the supercooled liquid with respect to the crystal, determined from calorimetric and expansivity measurements over the same T–P range of dynamics investigation. The AG relation, predicting linear dependence between the logarithmic of structural relaxation time and the reciprocal of the product of temperature with configurational entropy, was successfully tested. Actually, a bilinear relation between S_exc and S_C was found, with different proportionality factors in isothermal and isobaric conditions. Using such results, we derived an equation for predicting the pressure dependence of the glass transition temperature, in good accordance with the experimental values in literature.     

Synthesis and characterization of new polystyrenes containing tributyltin moieties linked to the aromatic ring through a methylenic spacer

Novel polymeric derivatives bearing tributyltin carboxylate moieties in the side chain were synthesized. The coordination at tin in solution and in the solid state was investigated by both Sn‐NMR and FT‐IR: the metal atom appears completely tetracoordinated in chloroform solution, while in the solid state all polymeric products exhibit both tetra‐ and pentacoordination at tin, the latter increasing with the amount of tin containing units. No evidence of tin leaching by hydrolysis of the organometallic ester was observed for these materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5372–5383, 2004     

Existence and qualitative properties of concentrating solutions for the sinh-Poisson equation

We prove the existence of nodal solutions for – u = sinhu with Dirichlet boundary conditions in bounded, 2D, smoothand non-smooth domains. Indeed, for positive and small enough,we show that there exist at least two pairs of solutions, whichchange sign exactly once, whose nodal lines intersect the boundary.     

Lattice-ordered Abelian groups and Schauder bases of unimodular fans

Baker-Beynon duality theory yields a concrete representation of any finitely generated projective Abelian lattice-ordered group in terms of piecewise linear homogeneous functions with integer coefficients, defined over the support of a fan . A unimodular fan over determines a Schauder basis of : its elements are the minimal positive free generators of the pointwise ordered group of -linear support functions. Conversely, a Schauder basis of determines a unimodular fan over : its maximal cones are the domains of linearity of the elements of . The main purpose of this paper is to give various representation-free characterisations of Schauder bases. The latter, jointly with the De Concini-Procesi starring technique, will be used to give novel characterisations of finitely generated projective Abelian lattice ordered groups. For instance, is finitely generated projective iff it can be presented by a purely lattice-theoretical word.

     

Intramolecular vibrational force fields for linear carbon chains through an adaptative linear scaling scheme

In this work, the vibrational force fields of hydrogen-capped oligoynes of increasing chain lengths are investigated by means of density functional theory calculations. It is shown that the interaction force constants between CC stretching coordinates decrease slowly with the distance between the two bonds considered. The consequence for the frequency dispersion of longitudinal optical (LO) phonons of an infinite polyyne chain is discussed and related to the observed behavior of the spectra of finite-size molecules. Effects of the exchange-correlation functional and of the basis set on the vibrational force constants are also investigated and the need for a scaling procedure is pointed out. Accordingly, new force fields which allow predictions in very good quantitative agreement with the available experimental data for oligoynes have been obtained, providing a sound assignment of alpha and beta lines.     

Pahs and trace elements in PM(2.5) at the Venice Lagoon

The results of an experimental analysis carried out to investigate PM(2.5) concentration levels and the content of polycyclic aromatic hydrocarbons, as well as inorganic trace elements in the atmospheric particles are presented. Measurements were taken with a micrometeorological station equipped with an optical PM(2.5) detector, and simultaneously, particles were collected on filters for subsequent chemical analyses. The average value of daily PM(2.5) concentration is 21.5 ug/m3 and real-time measurements indicate that the average concentration during the day (8 am to 8 pm) is about 25% lower than the nocturnal average. Short-time averages of PM2.5 decrease when the wind speed increases as consequence of the more efficient mixing. Meteorological measurements indicate the presence of a local daily (breeze) circulation with wind blowing from the Alps or the Adriatic Sea and, during this circulation, larger concentrations were observed, with wind coming from the Alps. Days of high PM(2.5) concentration with dominant anthropic or with prevalent crustal contributions were identified. Regarding trace metals, their average concentrations are comparable to those found in others urban areas, except for Cd (3 ng m(-3)), probably due to the presence of glass-works in Murano. The highest concentrations are observed for K (99 ng m(-3)) and Na (73 ng m(-3)), which are the main constituents of marine spray, while the lowest concentrations are observed for elements such as Cs and Co (respectively 0.01 and 0.02 ng m(-3)). Also the concentrations of PAH are comparable with those of other industrial areas, as their sum ranges from 0.16 ng m(-3) to 3.73 ng m(-3), but if considered as B(a)P toxicity equivalent, they are largely lower (0.036 +/- 0.026 ng m(-3)). From the analyses of discriminating ratios, it has been found that the main origin of PAH in PM(2.5) samples may be petrogenic, probably related to the presence of refinery and petrochemical plants on the mainland, although the contribution of combustion processes cannot be excluded.