Nanostructured silicon as a photonic material

Photonics applications of silicon are presented. In particular it is demonstrated that silicon when rendered low dimensional, e.g. in form of nanocrystals or quantum wires, can be turned into an active photonic materials which shows light amplification characteristics, non-linear optical effects, photon confinement in both one and two dimensions, photon trapping with evidences of light localization, and gas sensing properties.     

Balloon program for hard-X-ray astronomy

Summary An observation program of X-ray sources in the (20÷200) keV energy band by means of a balloon-borne NaI(Tl) seintillator array was undertaken in 1980. Three balloon flights have been performed and 10 X-ray rources observed, some more than once. We present details of this balloon program and results obtained from the analysis of the Crab observation performed in October 1980. Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–June 1984.     

Influence of sol-gel coatings on crack initiation by vickers indentation in soda-lime glass

In this work an indentation technique was used to study the effect of the sol-gel coatings of soda-lime glasses on crack formation. The tendency of samples to develop radial cracks has been evaluated by measuring their number in correspondence with the Vickers impressions as a function of the applied load. Silica coatings of different thickness were obtained from alcoholic solutions of TEOS by the dipping technique on glass sheets with different degrees of surface hydration.

All the coated samples show a lower crackability compared with the uncoated ones. It was found that this parameter is influenced by layer thickness, heat treatment temperature and by the degree of galss surface hydration.     

Self-consistent-field CNDO/BW cluster model of covalent solids

We have suggested a parametrization scheme for the self -consistent CNDO/BW method suitable to model the electronic structure of perfect and locally perturbed covalent solids. By working on small clusters we have carried out calculations for diamond perfect crystal and for nitrogen replacing a carbon atom in the lattice. The results show that the methos is accurate to calculate one electron energy-eigenvalues and total energies.     

Interconversion of benzofurazandione monoximes

The preparation of 5-hydroxy-4-nitroso- and 7-hydroxy-4-nitrosobenzofurazan as well as of their 6-chloro and methyl derivatives is described and the oxime structure of these compounds is established. NMR spectra of benzofurazan-4,5-dione-4-monoxime and benzofurazan-4,7-dione-4-monoxime show evidence for an interconversion, in solution, of two monoximes, the 4,5- and 4,7-derivative prevailing in organic solvents and aqueous alkaline media, respectively. Chloro and methyl derivatives of benzofurazan-4,5- and 4,7-dione-4-monoximes show a similar interconversion in organic solvents.