From Affiliation Matrices to Adjacency Matrices: Methods and Techniques for the Analysis of Centrality

In the analysis of 2-mode networks, the transition from affiliation matrices to adjacency matrices formalizes the information on overall actors' participation in the occasions, in a way that does not allow to exploit the whole amount of information in some analysis, such as centrality. In this article, I propose a procedure for the calculation of a different and more informative adjacency matrix; moreover, I propose an adaptation for Freeman centrality indices; this adaptation accounts for the different organization of the information on the intersubset ties, which allows the computation of centrality using all the available information. Finally, I empirically illustrate the introduced procedures, and the information they allow to retrieve, analyzing a real 2-mode network known in the literature.     

A new observable to measure the top quark mass at hadron colliders

The $t\bar{t}+\mbox{1-jet} + X$ differential cross-section in proton?Cproton collisions at 7?TeV centre of mass energy is investigated with respect to its sensitivity to the top quark mass. The analysis includes higher order QCD corrections at NLO. The impact of the renormalization scale (?? _R), the factorization (?? _F) scale and of the choice of different proton??s PDF (parton distribution function) has been evaluated. In this study it is concluded that differential jet rates offer a promising option for alternative mass measurements of the top quark, with theoretical uncertainties below 1 GeV.     

Molecular dynamics of polymers with explicit but frozen hydrogens

A new form of holonomic constraint, called a conic constraint, is introduced for the purpose of eliminating the fast vibrations of hydrogen atoms in molecular simulations of systems of aliphatic chains. It can easily be combined with bond constraints in SHAKE/RATTLE algorithms for which a unified tolerance criterion is defined. The new form of constraint allows the use of rather large time steps (in the 2–3 fs range). The procedure is illustrated for a full atomic model of polypropylene.