Parity Violation in Astrophysics

Core collapse supernovae are gigantic explosions of massive stars that radiate 99% of their energy in neutrinos. This provides a unique opportunity for large scale parity or charge conjugation violation. Parity violation in a strong magnetic field could lead to an asymmetry in the neutrino radiation and recoil of the newly formed neutron star. Charge conjugation violation in the neutrino-nucleon interaction reduces the ratio of neutrons to protons in the neutrino driven wind above the neutron star. This is a problem for r-process nucleosynthesis in this wind. On earth, parity violation is an excellent probe of neutrons because the weak charge of a neutron is much larger than that of a proton. The Parity Radius Experiment (PREX) at Jefferson Laboratory aims to precisely measure the neutron radius of $^{208}$Pb with parity violating elastic electron scattering. This has many implications for astrophysics, including the structure of neutron stars, and for atomic parity nonconservation experiments.}Comment: 4 pages, 2 figures, proceedings of PAVI04 conference in Grenoble, Franc

Comparação entre o método da gota pendente e o método da gota girante para medida da tensão interfacial entre polímeros Comparison between the pendant drop and spinning drop method to measure interfacial tension between polymers

Dois instrumentos, um deles baseado no princípio da gota pendente e o outro baseado no método da gota girante, para medir a tensão interfacial entre polímeros, são apresentados e comparados aqui. Com ambos instrumentos foi possível visualizar a gota de polímero "on line". Os instrumentos mostraram-se complementares quanto às suas áreas de aplicação. O método da gota pendente deve ser usado quando as quantidades de polímero são limitadas ou quando o polímero mais denso é opaco. O método da gota girante deve ser usado quando a degradação térmica pode ser um problema ou quando o polímero menos denso é opaco.<br>In this paper two apparatuses, one based on the principle of the pendant drop method and one based on the principle of the spinning drop are presented and compared. With both apparatuses it was possible to view the drop in real time and calculate the interfacial tension on-line. The two equipments were shown to be complementary in their use. The pendant drop method should be used when there are limited quantities of polymer and/or the denser polymer is opaque. The spinning drop method should be used when thermal degradation could be a problem and/or when the lighter polymer is opaque