The present invention is directed to novel polypeptides and to nucleic acid molecules encoding those polypeptides. The device consists of a loading chamber and two downwardly expanding sealable chambers arranged in a row beneath each other, and separated from each other and from the chamber of the installation by closing elements. The popularity prediction module predicts a popularity of the electronic media item based on the comparing, before providing the electronic media item to a user. From this posterior distribution, multiple images with the different contrast characteristics are reconstructed. In one aspect, a method of generating nucleic acid fragments having a customized fragment size distribution is provided comprising obtaining a master pool of nucleic acid molecules to be fragmented; fragmenting at least two independent aliquots of the master pool of nucleic acid molecules in separate reactions, wherein the fragmentation conditions are identical except for a single variable.