Finite-size scaling of partition function zeros and first-order phase   transition for infinitely long Ising cylinder
  The critical properties of an infinitely long Ising strip with finite width L joined periodically or antiperiodically are investigated by analyzing the distribution of partition function zeros. For periodic boundary condition, the the leading finite-size scaling of partition function zeros and its corrections are given. For antiperiodic boundary condition, the critical point of 2D Ising transition is one of the loci of the zeros, and the associated non-analyticity is identified as a first-order phase transition. The exact amount of the latent heat released by the transition is 4/L. 
Ming-Chang Huang, Tsong-Ming Liaw, Yu-Pin Luo and Simon C. Lin