In March 2006, Nature published a special report that called into question the validity of the results of the Purdue experiments.[16] The report quotes Brian Naranjo of the University of California, Los Angeles to the effect that neutron energy spectrum reported in the 2006 paper by Taleyarkhan, et al. was statistically inconsistent with neutrons produced by the proposed fusion reaction and instead highly consistent with neutrons produced by the radioactive decay of Californium 252, an isotope commonly used as a laboratory neutron source .[2][25]