Substructure dependence of jet cross sections at HERA and determination   of alpha_s
  The substructure of jets has been studied in terms of the jet shape and subjet multiplicity and these quantities used to tag gluon- and quark-initiated jets. Cross sections are presented for gluon- and quark-tagged jets which exhibit the expected behaviour of the underlying parton dynamics. The value of alpha_s(M_Z) of alpha_s(M_Z) = 0.1176 +- 0.0009 (stat.) ^{+0.0009}_{-0.0026} (exp.) ^{+0.0091}_{-0.0072} (th.) was extracted from the measurements of jet shapes in deep inelastic scattering. 
M. Wing (On behalf of the ZEUS Collaboration)