In this paper we report Grand Canonical Monte Carlo simulations to characterize the competitive trapping of CO and N 2 molecules into clathrates, for various gas compositions in the temperature range from 50 to 150 K. The simulations evidence a preferential trapping of CO with respect to N 2 . This leads to the formation of clathrates that are preferentially filled with CO at equilibrium. This is irrespective of the composition of the gas phase, the fugacity and the temperature. Moreover, the results of the simulations show that the small cages of the clathrate structure are always filled in first place, and this is independent of either the guest structure or the temperature. This issue has been associated to the rather significant differences in the calculated heats of encapsulation (∼2-3 kJ/mol) between the small and the larges cages. In addition, calculations with the simplified ideal adsorbed solution theory (IAST) are developed for allowing a comparison with the results arising from the GCMC simulations. Interestingly, this shows that the occupancy isotherms of the mixed N 2 -CO clathrates can be perfectly represented by knowing the occupancy isotherms of the corresponding singleguest clathrates. This suggests that experiments performed with the single guest CO and N 2 clathrates might be sufficient to get information concerning the corresponding mixed clathrates by using the IAST approach.

Abstract. We use the directed networks between articles of 24 Wikipedia language editions for producing the Wikipedia Ranking of World Universities (WRWU) using PageRank, 2DRank and CheiRank algorithms. This approach allows to incorporate various cultural views on world universities using the mathematical statistical analysis independent of cultural preferences. The Wikipedia ranking of top 100 universities provides about 60 percent overlap with the Shanghai university ranking demonstrating the reliable features of this approach. At the same time WRWU incorporates all knowledge accumulated at 24 Wikipedia editions giving stronger highlights for historically important universities leading to a different estimation of efficiency of world countries in university education. The historical development of university ranking is analyzed during ten centuries of their history.