Measurements of Rb, AFBb, and AFBc in e+e- Collisions at 130-189 GeV           
  
        The cross-section ratio                                                
        Rb = sigma(e+e- --> bbbar )/sigma(e+e- --> qqbar)                      
        and the bottom and charm forward-backward asymmetries AFBb and AFBc    
        are measured using event samples collected by the OPAL detector        
        at centre-of-mass energies between 130 and 189 GeV.                    
        Events with bottom quark production are selected with                  
        a secondary vertex tag, and a hemisphere charge algorithm is used to   
        extract AFBb. In addition, the bottom and charm asymmetries are        
        measured using leptons from semileptonic decays of heavy               
        hadrons and pions from D* decays.                                      
        The results are in agreement with the Standard Model predictions.      
  
 Parallel session :5                   
 Plenary  session :6a