Genes that are essential for growth in yeast were screened to identify those involved in arsenite sensitivity. We found that the knockdown of YPT1, ERG8, or RKI1 enhanced arsenite sensitivity in yeast.

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We give a new construction of tournaments satisfying the quasi-random property based on digraph spectra and a digraph-version of the expander-mixing lemma. We also discuss an application of our construction to the proof of the NP-hardness of the feedback arc set problem for tournaments.

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A tournament is an oriented complete graph. The problem of ranking tournaments was firstly investigated by P. Erdős and J. W. Moon. By probabilistic methods, the existence of "unrankable" tournaments was proved. On the other hand, they also mentioned the problem of explicit constructions. However, there seems to be only a few of explicit constructions of such tournaments. In this note, we give a construction of many such tournaments by using skew Hadamard difference sets which have been investigated in combinatorial design theory.2010 Mathematics Subject Classification. 05C20.