Quantized tension: Stringy amplitudes with Regge poles and parton   behavior
  We propose stringy hadronic amplitudes that combine some of the features of sister trajectories and running tension. By summing over string amplitudes with varying Regge trajectories that have integer tension and converging intercept, we obtain parton hard-scattering and Regge soft-scattering behaviors, while preserving discrete poles in both momentum and angular momentum. 
Oleg Andreev and Warren Siegel