  Cross-sections for hadronic, b-bbar and lepton pair final states in e+e-
collisions at sqrt(s) = 183 GeV, measured with the OPAL detector at LEP, are
presented and compared with the predictions of the Standard Model.
Forward-backward asymmetries for the leptonic final states have also been
measured. Cross-sections and asymmetries are also presented for data recorded
in 1997 at sqrt(s) = 130 and 136 GeV. The results are used to measure the
energy dependence of the electromagnetic coupling constant alpha_em, and to
place limits on new physics as described by four-fermion contact interactions
or by the exchange of a new heavy particle such as a leptoquark, or of a squark
or sneutrino in supersymmetric theories with R-parity violation.
