A deterministic finite automaton (DFA) separates two strings w and x if it accepts w and rejects x. The minimum number of states required for a DFA to separate w and x is denoted by sep(w, x). The present paper shows that the difference ∣∣sep(w, x)− sep(w, xR)∣∣ is unbounded for a binary alphabet; here w stands for the mirror image of w. This solves an open problem stated in [Demaine, Eisenstat...

Regulation of genomic activity occurs through the manipulation of DNA by competent mechanoenzymes. Force-clamp optical tweezers that allow the structural dynamics of the DNA molecule to be measured were used here to investigate the kinetics of mechanically-driven strand reannealing. When the force on the torsionally unconstrained λ-phage DNA is decreased stepwise from above to below the overstr...