A significant part of eukaryotic non-coding DNA is viewed as the passive result of mutational processes, such as the proliferation of mobile elements. However, sequences lacking an immediate utility can nonetheless play a major role in the long-term evolvability of a lineage, for instance by promoting genomic rearrangements. They could thus be subject to an indirect selection. Yet such a long-term effect is difficult to isolate either in vivo or in vitro. Here, by performing in silico experimental evolution, we demonstrate that, under low mutation rates, the indirect selection of variability promotes the accumulation of non-coding sequences: Even in the absence of self-replicating elements and mutational bias, non-coding sequences constituted an important fraction of the evolved genome, because the indirectly selected genomes were those that were variable enough to discover beneficial mutations. On the other hand, high mutation rates lead to compact genomes, much like the viral ones, although no selective cost of genome size was applied: The indirectly selected genomes were those that were small enough for the genetic information to be reliably transmitted. Thus the spontaneous evolution of the amount of non-coding DNA strongly depends on the mutation rate. Our results suggest the existence of an additional pressure on the amount of non-coding DNA, namely the indirect selection of an appropriate trade-off between the fidelity of the transmission of the genetic information and the exploration of the mutational neighbourhood. Interestingly, this trade-off resulted robustly in the accumulation of non-coding DNA so that the best individual leaves one offspring without mutation (or only neutral ones) per generation.

The Coulomb interaction between localized electrons is shown to create a 'soft' gap in the density of states near the Fermi level. The new temperature dependence of the hopping DC conductivity is the most important manifestation of the gap. The form of the density of states within the gap is discussed.

In this paper we consider the properties of the disordered systems, when the mean free path of electrons is more or comparable with its wave length, i.e. some higher the localization edge. It is shown that the electron-electron interaction in this situation leads to an anomaly in the density of states near the Fermi level. We argue that this anomaly causes that of the tunnel resistance. The minimum in the temperature dependence of the resistivity in the disordered metals may also be due to a similar mechanism.

We present a theory of interstitial Mn in Mn-doped ferromagnetic semiconductors. Using density-functional theory, we show that under the nonequilibrium conditions of growth, interstitial Mn is easily formed near the surface by a simple low-energy adsorption pathway. In GaAs, isolated interstitial Mn is an electron donor, each compensating two substitutional Mn acceptors. Within an impurity-band model, partial compensation promotes ferromagnetic order below the metal-insulator transition, with the highest Curie temperature occurring for 0.5 holes per substitutional Mn.