The paper that was supposed to be online on the 7^th is finally up. A highly unexpected strong correlation between fixation probability of nonsynonymous mutations and mutation rate:

Under prevailing theories, the nonsynonymous-to-synonymous substitution ratio (i.e. K_a/K_s), which measures the fixation probability of nonsynonymous mutations, is correlated with the strength of selection. In this article, we report that K_a/K_s is also strongly correlated with the mutation rate as measured by K_s, and that this correlation appears to have a similar magnitude as the correlation between K_a/K_s and selective strength. This finding cannot be reconciled with current theories. It suggests that we should re-evaluate the current paradigms of coding-sequence evolution, and that the wide use of K_a/K_s as a measure of selective strength needs reassessment.

FYI to be simple about it nonsynonymous mutations change the amino acid coded for and synonymous ones do not. Fixation is when the frequency of an allele in the population ~100%, that is, it has become a monomorphic locus (this tends to be common for genetically coded traits which show no intraspecies variation, at least heritable variation).