We discuss whether the minimally coupled massless Klein-Gordon and Dirac fields have well defined quasinormal modes in single horizon, asymptotically flat two-dimensional black holes. To get the result we solve the equations of motion in the massless limit and we also calculate the effective potentials of Schrödinger type equations. Furthermore we calculate exactly the quasinormal frequencies of the Dirac field propagating in the two-dimensional uncharged Witten black hole. We compare our results on its quasinormal frequencies with other already published.

We calculate exactly the quasinormal frequencies of Klein-Gordon and Dirac test fields propagating in two-dimensional uncharged Achucarro-Ortiz black hole. For both test fields we study whether the quasinormal frequencies are well defined in the massless limit. We use their values to discuss the classical stability of the quasinormal modes in uncharged Achucarro-Ortiz black hole and to check the recently proposed Time Times Temperature bound. Furthermore we extend some of these results to the charged Achucarro-Ortiz black hole.

The star formation rate (SFR) was determined from a sample of 36 late-type galaxies (14 dS and 22 Sm), from the SFR(H α ) and far ultraviolet (FUV) flux. We found that the SFR(FUV) is higher in most cases, larger for Sm galaxies and smaller for barred galaxies, for any morphological type, in both diagnostic methods. In addition, a study of the spatial distribution of star formation within these galaxies was made. We concluded that there is no preferential place for the star formation. Finally, we studied the role of the diffuse ionized gas in the SFR value; we found that the H α flux contribution from this gas should not be included in the SFR determination unless it is verified that leaking photons are the only source of the neutral gas ionization.