Organic contamination in clams,Venerupis aurea laeta and Cerastoderma edule glaucum,from Sicily (Italy)

Two species of edible clams Venerupis aurea laeta and Cerastoderma edule glaucum from Ganzirri Lake (Sicily, Italy) were investigated to determine OCP and PCB residues by GC-MS. Thirty-five samples were examined for two years in order to perform: a) their actual contamination; b) the daily dietary exposure of seafood consumers to the pollutants in question. In all the clams analysed in this study, PCB and OCP (4,4′-DDE) residues are always below the limits fixed by law. It seems that there is some seasonality of concentrations observed. In fact the more high concentrations of residues are detected in the hot months, for both species and years. Given the consumption of clams and the values obtained in this study for the two species analysed, it is possible estimate that the average daily dietary intake of NDL-PCB and of 4,4′-DDE for adults is really low.     

Synthesis of allylic alcohols from oxazolinyloxiranes

Lithium diisopropylamide (LDA) (or s-BuLi/TMEDA) in diethyl ether promotes smooth ring opening of oxazolinyl alkyl oxiranes to give oxazolinyl allylic alcohols, which are masked Baylis-Hillman adducts, in good to excellent yields. An E2-E1cb-like syn-beta-elimination is proposed to explain the easy base-promoted isomerization of the studied oxiranes.     

$ B \to D^{(*)}$ transitions in a quark model

We propose a constituent quark model to evaluate heavy decay constants and form factors relevant for semileptonic transitions. We show that the model reproduces the scaling laws dictated by the spin-flavor symmetry in the heavy quark limit and describes quite well the experimental data.Received: 29 December 2004, Published online: 21 February 2005     

Power-law time distribution of large earthquakes

We study the statistical properties of time distribution of seismicity in California by means of a new method of analysis, the diffusion entropy. We find that the distribution of time intervals between a large earthquake (the main shock of a given seismic sequence) and the next one does not obey Poisson statistics, as assumed by the current models. We prove that this distribution is an inverse power law with an exponent mu=2.06+/-0.01. We propose the long-range model, reproducing the main properties of the diffusion entropy and describing the seismic triggering mechanisms induced by large earthquakes.     

Lattices on tetrahedral partitions

In this paper, four-pencil lattices on tetrahedral partitions are studied. The explicit representation of a lattice, based upon barycentric coordinates, enables us to extend the lattice from a single tetrahedron to a tetrahedral partition. It is shown that the number of degrees of freedom is equal to the number of vertices of the tetrahedral partition. The proof is based on a lattice split approach.      

On the stability of vibrations of a particle in a plane constrained by identical non-linear springs

This is a study on the stability of movement of a particle subject to displacement on a plane and linked to two supports fixed by identical non-linear springs. It is demonstrated that even a slight “softening” non-linearity completely modifies the characteristics of the stability of the system.