  The PHENIX experiment at RHIC has measured single electron spectra in
proton-proton, deuteron-gold and gold-gold collisions at sqrt(s_NN)=200 GeV.
The photonic contribution (photon conversions and Daltiz decays) is subtracted
from the inclusive spectra resulting in non-photonic electron spectra. The
principal source of non-photonic electrons is the semi-leptonic decay of charm
and bottom mesons. The implications for heavy flavor production in hot and cold
nuclear systems are discussed.
