Preliminary report on the large halo event TADJIKISTAN

Summary A large halo event, TADJIKISTAN, observed recently by the Pamir Collaboration, consists of a halo (diameter ∼2 cm) and of a large number (∼2000) of high-energy showers, distributed over an area ofR∼20 cm. The total observed energy in the halo is estimated to be 4.8·10⁴ TeV. The characteristics of the event are compared with those of ANDROMEDA, another large event observed by the Chacaltaya Collaboration. The observed attenuation mean free path of hadrons, Λ/λ_p = 1.41 _−0.32 ^+0.21 is compatible with that of pions, indicating that the hadrons in the event are not exotic on average. Paper presented at the Special Session on very high-energy cosmic-ray interactions (superfamilies) of the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Equilibrium anionic polymerization of 4,7-dioxaoctanal and n-octanal

Equilibrium anionic polymerization of 4,7-dioxaoctanal (DOA) and n-octanal (OA) was carried out in tetrahydrofuran in the temperature range of ?90 to ?68°C, and thermodynamic parameters were evaluated as follows: ΔH_ss = ?4.0 ± 0.1 kcal/mole, ΔS_ss = ?18.4 ± 0.5 cal/mole-deg, and T_c,ss = ?56°C for the DOA system; ΔH_sc = ?3.4 ± 0.1 kcal/mole, ΔS_sc = ?15.7 ± 0.4 cal/mole-deg, and T_c,sc = ?59°C for the OA system. Comparison of these values with those in the cases of β-methoxypropionaldehyde and n-valeraldehyde made it clear that the aliphatic aldehyde having a longer alkyl group polymerizes with smaller changes of enthalpy and entropy and that the polar-substituted aldehydes have higher polymerizability than the corresponding unsubstituted aliphatic aldehydes in the temperature range studied. These effects of substituents are interpreted from the viewpoint of the intermolecular interactions of polar groups in monomers and their polymers.     

Computational comparison of charge neutralisations of conductors and insulators with corona ionisers

We report a numerical investigation of phenomena of charge neutralisations of insulators and conductors with a balanced DC or AC ioniser using 2-D cylindrical electrohydrodynamic modelling. The early-phase phenomena of the insulator charge neutralisation are complicated and significantly different from the conductor ones, which indicates that the evaluation by the standard test may lead to potential problems in practical applications. In addition, the results of simulations demonstrated that, in the insulator charge neutralisation, ionisers themselves can cause latent hazards during neutralisation. We propose proper use of ionisers and the standard test to avoid such hazards.     

Accelerated electrocyclic ring-opening of benzocyclobutenes under the influence of a beta-silicon atom

A significant acceleration effect of a beta-silicon atom was observed on the electrocyclic ring-opening reaction of benzocyclobutene derivatives to form o-quinodimethanes. This acceleration effect could be attributed to an electronic sigma-donating nature of the C(alpha)-Si(beta) bond, associated with alpha-anion driven pericyclic reactions.