Improved constraints on sterile neutrinos in the MeV to GeV mass range

Improved upper bounds are presented on the coupling |Uₑ₄|² of an electron to a sterile neutrino ν₄ from analyses of data on nuclear and particle decays, including superallowed nuclear beta decays, the ratios ${R}_{e/{μ}}^{({π})}=BR({{π}}⁺{→}{e}⁺{{ν}}ₑ)/BR({{π}}⁺{→}{{μ}}⁺{{ν}}_{{μ}})$, ${R}_{e/{μ}}(K)$, ${R}_{e/{τ}}^{({D}ₛ)}$, and ${B}ₑ₂⁺$ decay, covering the mass range from MeV to GeV.