Mark Johnson, the Arthur T. Kemp Professor of Chemistry at Yale University, will present a public lecture "From proteomics to homeland security: Why mass-spectrometry is key to emerging tehnologies in the molecular sciences," at 2 p.m. Thursday, Oct. 29, in 324 McKinley Hall. Johnson also will give a scientific lecture "Navigating the potential landscapes of H-bonded networks with Ar-mediated, pump-probe vibrational spectroscopy of cluster ions" at 3:30 p.m. Friday, Oct. 30, in 324 McKinley Hall.