A Lower Bound of the First Eigenvalue of a Closed Manifold with Negative   Lower Bound of the Ricci Curvature
  Along the line of the Yang Conjecture, we give a new estimate on the lower bound of the first non-zero eigenvalue of a closed Riemannian manifold with negative lower bound of Ricci curvature in terms of the in-diameter and the lower bound of Ricci curvature. 
Jun Ling