Results from PLUTO at PETRA

Results obtained at the e/sup +/e/sup -/ storage ring PETRA by the PLUTO collaboration at c.m. energies of 13, 17 and 27.4 GeV are presented. New limits on QED cut-off parameters are determined from Bhabha scattering; at 27.4 GeV the limits are Lambda /sub +/>38 GeV and Lambda /sub -/>60 GeV. The measured values of the total hadronic cross section, and the study of the jet character of the hadronic events are well consistent with the expected production of b mesons (with q/sub b/=1/3), but do not require additional new quarks with charge 2/3. Hadronic events from two-photon exchange processes are observed with comparable rates as events from one-photon exchange. First results on the hadronic cross section in gamma gamma collisions are given. (8 refs).