ACM vector bundles on scrolls

Here we show that certain low rank ACM vector bundles on scrolls over smooth curves are iterated extensions of line bundles. Partially supported by MIUR and GNSAGA of INDAM (Italy)     

On the symmetric products of a curve

Both authors are supported by MURST and CNR of Italy.     

Competitive systems with stage structure of distributed-delay type

This paper considers a delay differential equation model for the interaction among n species, the adult members of which are in competition. For each of the n species the model incorporates an infinite distributed time delay which represents the time from birth to maturity of that species. Thus, the time delays appear in the adult recruitment terms. The dynamics of the model are determined, and sharp global stability criteria are established for the interior equilibrium as well as the axial equilibrium.     

Weighted composition operators and locally convex algebras

The Gleason-Kahane-Zelazko theorem characterizes the continuous homo-morphism of an associative, locally multiplicatively convex, sequentially complete algebra A into the field C among all linear forms on A. This characterization will be applied along two different directions. In the case in which A is a commutative Banach algebra, the theorem yields the representation of some classes of continuous linear maps A:A→A as weighted composition operators, or as composition operators when A is a continuous algebra endomorphism. The theorem will then be applied to explore the behaviour of continuous linear forms on quasi-regular elements, when A is either the algebra of all Hilbert-Schmidt operators or a Hilbert algebra.     

Analysis of a perforated panel for the correction of low frequency resonances in medium size rooms

This work illustrates an engineering approach for the analysis of plywood/fibreglass perforated panels, to be used for the linearisation of the frequency response of medium size rooms below 200 Hz. The sound absorption coefficient of these panels is computed, by means of coupled acoustical/structural finite element (FEM) analyses, as a function of the frequency. The comparison between the results given by a complete numerical model of the panel, and those provided by a simplified numerical model, in which only one hole and surrounding material (wood, air, and fibreglass) are described, shows that the second computational approach provides essentially the same results as the former one, at a quite reasonable cost. The FEM results allow us to understand some details about the air motion inside the panel, and to define suitable assumptions for the construction of a simplified analytical model of the panel. Both the numerical and the analytical results are finally compared to experimental data obtained by means of pressure-particle velocity measurements.     

Metal directed assembly of ditopic containers and their complexes with alkylammonium salts

A new self-folding cavitand has been assembled through metal coordination to give a thermodynamically stable ditopic receptor of nanosize dimensions which has been used in the reversible binding of di-alkylammonium and n-alkylammonium salts.