102,058 research outputs found
Lazzati (G.). Teofilo d'Alessandria
No full textJanin R. Lazzati (G.). Teofilo d'Alessandria. In: Échos d'Orient, tome 38, n°195-196, 1939. pp. 496-497
Rec. di: G. Alberigo (a c. di), Giuseppe Lazzati 1909-1986. Contributi per una biografia
No full textSi analizza il volume dedicato alla figura di Giuseppe Lazzati, intellettuale cattolico del Novecento
Constraints on the emission mechanisms of gamma-ray bursts
No full textIf the emission of gamma-ray bursts were as a result of the synchrotron process in the standard internal shock scenario, then the typical observed spectrum should have a slope F nu proportional to nu(-1/2), which strongly conflicts with the much harder spectra observed. This directly follows from the cooling time being much shorter than the dynamical time. Particle reacceleration, deviations from equipartition, quickly changing magnetic fields and adiabatic losses are found to be inadequate to account for this discrepancy. We also find that in the internal shock scenario the relativistic inverse Compton scattering is always as important as the synchrotron process, and faces the same problems. This indicates that the burst emission is not produced by relativistic electrons emitting synchrotron and inverse Compton radiation
Constraints on the bulk Lorentz factor in the internal shock scenario for gamma-ray bursts
No full textWe investigate, independently of specific emission models, the constraints on the value of the bulk Lorentz factor Gamma of a fireball. We assume that the burst emission comes from internal shocks in a region transparent to Thomson scattering, and before deceleration caused by the swept-up external matter is effective. We consider the role of Compton drag in decelerating fast-moving shells before they interact with slower ones, thus limiting the possible differences in the bulk Lorentz factor of shells. Tighter constraints on the possible range of Gamma are derived by requiring that the internal shocks transform more than a few per cent of the bulk energy into radiation. Efficient bursts may require a hierarchical scenario, where a shell undergoes multiple interactions with other shells. We conclude that fireballs with average Lorentz factors larger than 1000 are unlikely to give rise to the observed bursts
Trattamento chirurgico-ortodontico della inclusione palatale completa dei canini per manenti e modifica della "Ballista Spring"
No full textTHE FOURTH DIMENSION OF SUSTAINABILITY FOR THE ARCHITECTURE PROJECT. REGULATORY INNOVATION FOR SOCIAL HOUSING
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