We investigated the room-temperature chemisorption of oxygen on Cu(1 0 0) and 1 1) using ambient-pressure X-ray photoelectron spectroscopy (APXPS). A shoulder-to-shoulder comparison between oxygen-gas titration two surfaces reveals that is more active for dissociative when are clean. The (2 2 × 2)R45o missing-row reconstruction appears in 0)’s LEED image after about 104 Langmuir exposure, where...

In this note we study multiple-ratio fractional 0–1 programs, a broad class of $$\mathcal {NP}$$ -hard combinatorial optimization problems. particular, under some relatively mild assumptions provide complete characterization the conditions, which ensure that single-ratio function is submodular. Then illustrate our theoretical results with assortment and facility location problems, discuss pract...