Alysis of the volatile constituents of food by headspace GC-MS with reversal of the carrier gas flow during sampling

A technique has been developed for performing headspace GC-MS analysis of volatile components of food, in which the carrier gas flow is reversed during sampling in order to overcome problems caused by the diffusion of substances not retained by the cold trap. Chromatographic profiles of volatile compounds from cheeses, obtained at room temperature, provide confirmation of the validity of the reversed flow technique, and the versatility of the system is evidenced by its successful application to both solid and liquid matrixes: the absence of any discrimination against the various components reveals its efficacy for compounds with a wide range of volatility. Addition of internal standards to the sample enables the use of the technique for quantitative analysis.     

Approximation of planar BV homeomorphisms by diffeomorphisms

We show that a planar BV homeomorphism can be approximated in the area strict sense, together with its inverse, with smooth or piecewise affine homeomorphisms.     

Prospects for e+e- physics at Frascati between the φ and the ψ

We present a detailed study, done in the framework of the INFN 2006 Roadmap, of the prospects for e⁺e^- physics at the Frascati National Laboratories. The physics case for an e⁺e^- collider running at high luminosity at the φ resonance energy and also reaching a maximum center of mass energy of 2.5 GeV is discussed, together with the specific aspects of a very high luminosity τ-charm factory. Subjects connected to kaon decay physics are not discussed here, being part of another INFN Roadmap working group. The significance of the project and the impact on INFN are also discussed. All the documentation related to the activities of the working group can be found in http://www.roma1.infn.it/people/bini/roadmap.html.     

First glances at the transversity parton distribution through dihadron fragmentation functions

We present first observations of the transversity parton distribution based on an analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets. The extraction of transversity relies on the knowledge of dihadron fragmentation functions, which we take from electron-positron annihilation measurements. This is the first attempt to determine the transversity distribution in the framework of collinear factorization.     

A new family of heavy transition metal coordination compounds and its application,I. Design,synthesis and characterization of volatile organohafnium precursors

The first three representatives of a new family of volatile organohafnium compounds suitable as metallo-organic chemical vapour deposition precursors were synthesized. A combination of cyclopentadienyl and alkoxo-ligands with a bicyclo[2.2.1]heptanc framework was used. Volatility at relatively low temperatures for hafnium compounds was found and the precursors were characterized by elemental analysis and spectroscopic methods (IR, ¹H and ¹³C NMR, mass spectrometry and mass-analysed ion kinetic energy spectroscopy). The outlook for use in hafnium functional materials synthesis was derived from the fragmentation data.     

Facile high-yield synthesis of pure, crystalline Mg(BH4)2

Magnesium borohydride, Mg(BH4)2, a long-sought candidate for efficient hydrogen storage chemisorption technology, has been obtained in a pure and crystalline form by two new synthetic routes in a hydrocarbon solvent. A first synthetic approach involves a metathetical reaction between organometallic magnesium compounds; a second route consists of an insertion reaction of BH3 species, released from BH3.S(CH3)2, into the Mg-C bonds of MgR2, with complete replacement of R groups with BH4 groups. Both methods, based on commercially available reagents, afford identical, pure, polycrystalline materials, identified by X-ray diffraction as the so-called low-temperature hexagonal form of Mg(BH4)2, stable below 180 degrees C, recently shown to possess a complex, unpredictable, crystal structure.     

Deterministic particle approximation for nonlocal transport equations with nonlinear mobility

We construct a deterministic, Lagrangian many-particle approximation to a class of nonlocal transport PDEs with nonlinear mobility arising in many contexts in biology and social sciences. The approximating particle system is a nonlocal version of the follow-the-leader scheme. We rigorously prove that a suitable discrete piece-wise density reconstructed from the particle scheme converges strongly in $L_{loc}^1$ towards the unique entropy solution to the target PDE as the number of particles tends to infinity. The proof is based on uniform BV estimates on the approximating sequence and on the verification of an approximated version of the entropy condition for large number of particles. As part of the proof, we also prove uniqueness of entropy solutions. We further provide a specific example of non-uniqueness of weak solutions and discuss the interplay of the entropy condition with the steady states. Finally, we produce numerical simulations supporting the need of a concept of entropy solution in order to get a well-posed semigroup in the continuum limit, and showing the behaviour of solutions for large times.     

Nucleon magnetic moments in an extended chiral constituent quark model

We present results for the nucleon magnetic moments in the context of an extended chiral constituent quark model based on the mechanism of the Goldstone boson exchange, as suggested by the spontaneous breaking of chiral symmetry in QCD. The electromagnetic charge-current operator is consistently deduced from the model Hamiltonian, which includes all force components for the pseudoscalar, vector and scalar meson exchanges. Thus, the continuity equation is satisfied for each piece of the interaction, avoiding the introduction of any further parameter. A good agreement with experimental values is found. The role of isoscalar two-body operators, not constrained by the continuity equation, is also investigated.     

Photoelectron spectroscopy of actinide organometallic compounds I. Bis(cyclooctatetraene)actinide(IV) complexes

The He(I) photoelectron spectra of the antinocene species Th(cot)₂ and U(cot)₂ (cot = cyclooctatetraene) have been determined. The 5f metal ionization has been detected at the onset of the uranocene spectrum. The low ionization energy region of both spectra is discussed in terms of simple qualitative molecular orbital scheme.