Transitions from coherent to incoherent state induced by anharmonic interaction

A non-linear stochastic oscillator driven by a coherent radiation field is studied. Analog simulation is shown to support the arguments of theory on the specific role of the fluctuation-dissipation process and/or anharmonic interaction in making valid a treatment in terms of a Boltzmann-like distribution of energy. The results of analog simulation show that at certain values of the excitation frequency a superimposition of a coherent and an incoherent state may appear thereby opening the way to a more exhaustive theoretical treatment of this problem.     

Posture as a chaotic system and an application to the Parkinson’s disease

In this work we investigate and compare a number of time series of stabilograms of healthy subjects and Parkinsonians. This is carried out by means of the chaos paradigm through the preliminary computation of the first minimum of the mutual information function and the embedding dimension (using false nearest neighbours) in order to obtain the correlation dimension as well as the largest Lyapunov exponent. We show that the postural act is indeed chaotic and especially that the latter two parameters do not allow to discriminate healthy subjects from parkinsonians. Moreover we report a discrepancy of our values with those found in previous works.     

Reagent-controlled diastereoselective aminations with a new chiral nosyloxycarbamate

The synthesis of a new chiral nosyloxycarbamate derived from Helmchen's auxiliary is described. Reactions performed with this aminating reagent successfully give the formation of diastereomeric allylic carbamates or diastereomeric aziridines starting from different kinds of olefins.     

Reaction of N1-acylacetamidrazones with trifluoroacetylvinyl ethers. Synthesis of new 4-trifluoromethyl- and 6-trifluoromethylpyridines

The reaction between N¹-acylacetamidrazones 1 and enol ether 2 is described. Depending on the reaction conditions and on the substitution pattern of amidrazones 2-acylhydrazino-4-methyl-6-trifluoro-methylpyridines 3 and/or 2-acylhydrazino-6-methyl-4-trifluoromethylpyridines 4 were obtained.     

Spectral Flow,Maslov Index and Bifurcation of Semi-Riemannian Geodesics

We give a functional analytical proof of the equalitybetween the Maslov index of a semi-Riemannian geodesicand the spectral flow of the path of self-adjointFredholm operators obtained from the index form. This fact, together with recent results on the bifurcation for critical points of strongly indefinite functionals imply that each nondegenerate and nonnull conjugate (or P-focal)point along a semi-Riemannian geodesic is a bifurcation point.In particular, the semi-Riemannian exponential map is notinjective in any neighborhood of a nondegenerate conjugate point,extending a classical Riemannian result originally due to Morse and Littauer.     

Compact factors in finally compact products of topological spaces

We present instances of the following phenomenon: if a product of topological spaces satisfies some given compactness property then the factors satisfy a stronger compactness property, except possibly for a small number of factors.The first known result of this kind, a consequence of a theorem by A.H. Stone, asserts that if a product is regular and Lindelöf then all but at most countably many factors are compact. We generalize this result to various forms of final compactness, and extend it to two-cardinal compactness. In addition, our results need no separation axiom.     

Stimulated self-trapped exciton emission in CsI:Pb

Defects of the type of V_K and Pb⁺ centres were created in CsI:Pb under the 4.03 eV XeCl laser line irradiation at 10 K. After irradiation, the self-trapped and localized exciton emission excited by the same XeCl laser line was observed as a result of the recombination of electrons, optically released from Pb⁺, with the V_K centres. A strongly superlinear dependence of the emission intensity on the excitation intensity was found for the 3.65 eV emission of the self-trapped exciton. A much weaker superlinearity was observed for the visible localized exciton emission. Optical amplification of the exciton emission was considered as the most probable reason of the observed phenomenon. At 10 K, optical gain G=3.74 was calculated for the self-trapped exciton emission.     

Algorithms and codes for the assignment problem

This paper analyzes the most efficient algorithms for the Linear Min-Sum Assignment Problem and shows that they derive from a common basic procedure. For each algorithm, we evaluate the computational complexity and the average performance on randomly-generated test problems. Efficient FORTRAN implementations for the case of complete and sparse matrices are given.Research supported by C.N.R., Progetto Finalizzato Informatica-SOFMAT, Italy.