Energy loss measurements and electronic properties of thianthren

Summary The dielectric and electronic properties of thianthren (C₆H₄(S)₂H₄C₆) are determined by means of optical reflectivity, absorption measurements and reflection electron energy loss spectroscopy. The experimental results are interpreted on the basis of a Complete Neglect of Differential Overlap (CNDO) calculation used in three different parametrization schemes. Emphasis is laid on the discussion of the problems which generally affect the analysis of electron energy loss spectra, and a procedure to obtain the complex dielectric function from electron energy loss measurements performed in the reflection mode is suggested. Work partially supported by the MURST through the GNSM.     

Efficient organocatalysis with a calix[4]pyrrole derivative

The 10α,20β-bis(4-nitrophenyl)-calix[4]pyrrole was found to act as an effective organocatalyst for the hetero Diels-Alder reaction of Danishefsky’s diene with aromatic aldehydes. This discovery is the first reported case of a calixpyrrole that exhibits organocatalytic activity.     

Problema di Dirichlet per l’equazione delle superfici di curvatura media assegnata con dato infinito

Riassunto In questo lavoro si studia il problema di Dirichlet per l’equazione delle superfici di curvatura media assegnata con dato infinito. Si dimostra una condizione necessaria e sufficiente affinchè esista una soluzione. Si dimostra pure un teorema di unicità.

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Summary In this paper we consider the Dirichlet’s problem for surfaces of prescribed mean curvature with infinite data. We prove a necessary and sufficient condition for the existence of the solution. Finally we prove an uniqueness theorem.

     

Determination of the pair polarizability of argon from the two-body cis spectrum

We present a moment analysis of the experimental two-body collision induced light scattering spectrum of argon which allows the determination of a three-parameter empirical form for the collision induced pair-polarizability anisotropy. The result of the calculation shows that beside the DID and the exponential short-range terms also an intermediate-range term gives an important contribution to the pair polarizability.     

On the instability in non-abelian gauge theories with constant magnetic flux

We discuss the stability of Yang-Mills fields in the framework of a sourceless scheme introduced by 't Hooft. We find that abelian magnetic field configurations in Yang-Mills theories are always unstable. A classification for the unstable modes is given.