Sull’equilibrio radiativo magnetodinamico di una massa gassosa stellare uniformemente rotante e gravitante

Sunto Si stabiliscono le equazioni differenziali che reggono l’equilibrio radiativo di una massa gassosa stellare uniformemente rotante e gravitante, altamente conduttrice dell’elettricità, in cui si genera un campo magnetico. Si considera il caso di una sfera in lenta rotazione uniforme. Ad Antonio Signorini nel suo 70^mo compleanno.     

Cover Picture

The cover picture shows the array of colors observed in the synthesis of the long-lived phosphorus radicals [Mes*MeP-PMes*](.) (3; Mes*=2,4,6-tBu(3)C(6)H(3)). These colors were obtained by layering a colorless solution of the electron-rich tetrakis(dimethylamino)ethylene (2) in acetonitrile onto a yellow solution of the phosphenium salt [Mes*MeP=PMes*](+)[O(3)SCF(3)](-) (1) in acetonitrile. An immediate intense green color characteristic of solute 3 formed at the phase boundary. At the same time orange-red crystals of 3 appeared and deposited on the walls of the container. The red color denotes the formation of the radical cation [(Me(2)N)(3)C(2)](.+). More about this reaction, which has allowed the first isolation of diphosphanyl radicals, is described by Geoffroy, Grützmacher, and co-workers on page 723 ff.     

Surface Reaction of Ozone at High Concentration with Isotactic And Syndiotactic Polypropylene

The surface reaction of isotactic and syndiotactic polypropylene (I-PP and S-PP) films with ozone was studied with FT-IR spectroscopy with differential scanning calorimetry (DSC) and making use of 2,2,4-trimethylpentane as a model compound of PP chain segment. I-PP and S-PP were found reactive toward ozone, and it was found that I-PP being more crystalline than S-PP, reacts more slowly with O₃. In fact, the pseudo first rate constant of I-PP with ozone was k’_I-PP = 8.0 × 10^?6 s^?1 while that of S-PP with ozone k’_S-PP = 1.3 × 10^?5 s^?1. However, the DSC study has shown that the ozone attack on I-PP or S-PP films is not selective and simultaneously destroys the amorphous and the crystalline phases. The ozone treated I-PP and S-PP films are much less resistant to the combined thermal and oxidative degradation reaction than the unexposed films. Thus, ozone is a naturally occurring pollutant at the soil level which accelerates the ageing of I-PP and S-PP materials.     

A Study on the Optically Active Polymer Poly‐β‐pinene

Poly‐β‐pinene (PBP) was obtained by radiation‐induced polymerization of monomer with γ radiation. The polymerizations were conducted both in vacuum and in the presence of air at different radiation doses up to 1–3 MGy. It was found that the presence of oxygen retards the polymerization rate and reduces the polymer yields and the radiation chemical yield suggesting that the polymerization mechanism involves free radicals. It is shown that PBP can also be obtained in low yields from β‐(‐)pinene polymerization with a free radical initiator. The chemical structures of the PBP radiopolymer and PBP obtained by a free radical initiator were studied by FT‐IR and ¹³C CP‐MAS NMR spectroscopy. The data shows that the PBP obtained have highly ordered structures, which is manifested also by the very high specific optical rotation which is about 3 times that of the starting monomer in the case of the radiopolymer and about 5 times in the case of the PBP prepared with the free radical initiator. In contrast, PBP obtained in high yields by cationic polymerization shows a very low specific optical rotation, much lower than that of the starting monomer and low regularity in chemical structure has been attributed to this polymer by FT‐IR and ¹³C CP‐MAS NMR spectroscopy. It is shown that PBP with high optical activity racemizes over an acidic catalyst.     

The NE detector for a long baseline neutrino oscillation experiment

The project of a large underground experiment, N^OE (Neutrino Oscillation Experiment), composed by modules of scintillating fiber calorimeter interleaved with TRD modules, total weight 6.7 ktons, is presented. This apparatus has been optimized for long baseline neutrino oscillation studies, in particular to be sensitive in the region of sin² 2θ and Δm² suggested by the atmospheric neutrino anomaly (fig. 3).     

O‐Doped Nanographenes: A Pyrano/Pyrylium Route Towards Semiconducting Cationic Mixed‐Valence Complexes

Herein we report an efficient synthesis to prepare O‐doped nanographenes derived from the π‐extension of pyrene. The derivatives are highly fluorescent and feature low oxidation potentials. Using electrooxidation, crystals of cationic mixed‐valence (MV) complexes were grown in which the organic salts organize into face‐to‐face π‐stacks, a favorable solid‐state arrangement for organic electronics. Variable‐temperature electron paramagnetic resonance (EPR) measurements and relaxation studies suggest a strong electron delocalization along the longitudinal axis of the columnar π‐stacking architectures. Electric measurements of single crystals of the MV salts show a semiconducting behavior with a remarkably high conductivity at room temperature. These findings support the notion that π‐extension of heteroatom‐doped polycyclic aromatic hydrocarbons is an attractive approach to fabricate nanographenes with a broad spectrum of semiconducting properties and high charge mobilities.