Thomas Behrendt

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We extend the recent approach of Papadimitrou and Yannakakis that relates the approximation properties of optimization problems to their logical representation. Our work builds on results by Kolaitis and Thakur who sytematically studied the expressibility classes Max n and Max n of maximization problems and showed that they form a short hierarchy of four(More)
Hydroxyl radicals (OH) are a key species in atmospheric photochemistry. In the lower atmosphere, up to ~30% of the primary OH radical production is attributed to the photolysis of nitrous acid (HONO), and field observations suggest a large missing source of HONO. We show that soil nitrite can release HONO and explain the reported strength and diurnal(More)
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