We show that every groupoid C*-algebra is isomorphic to its opposite, and deduce there exist C*-algebras are not stably C*-algebras, though many of them twisted C*-algebras. also prove the opposite algebra a section Fell bundle over natural bundle.

Arguing against efficiency is like arguing against motherhood and apple pie. How could anyone be against efficiency in health services? And when you look at the amounts of money needed to run a health system, as politicians frequently do, of course you want to use that money efficiently. In just about every policy or statement on health systems efficiency will be mentioned as one of the princip...

In order to analyze the singularities of a power series P (t) on the boundary of its convergent disc, we introduced the space Ω(P ) of opposite power series in the opposite variable s=1/t, where P (t) was, mainly, the growth function (Poincaré series) for a finitely generated group or a monoid [S1]. In the present paper, forgetting about that geometric or combinatorial background, we study the ...