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Aztec symbolism and quantum mechanical concepts are mixed to celebrate the Mexican Theoretical Physical Chemistry Meetings (RMFQT). The four bicephalous snakes are an allegory of the importance of symmetry in quantum systems, depicting the S4 group. The four pictographs just below it depict the five irreducible representations of that group in which the number of flowers corresponds to the dimensions of the representation. The snakes on both sides represent the creation and annihilation operators of the second quantization formalism. The two red circles and the glyph in the upper left corner indicate that this is part two of this special issue and the year 2012 of publication. A more detailed cover description by the artist, Renato Lemus, a theoretical chemist at the Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, can be found at the RMFQT site: