This paper answers a basic question about the Birman exact sequence in theory of mapping class groups. We prove that does not admit section over any subgroup $\Gamma$ contained Torelli group with finite index. A fortiori this proves there is no for finite-index full group. theorem was announced 1990 preprint G. Mess, but an error uncovered and described recent first author.

With the exploitation of rare earth ore, more and more REEs came into groundwater. This was a waste of resources and could be harmful to the organisms. This study aimed to find an efficient adsorption material to mitigate the above issue. Through doping sodium alginate (SA) with poly-γ-glutamate (PGA), an immobilized gel particle material was produced. The composite exhibited excellent capacity...

We exhibit crossed modules (i.e. certain 4 term exact sequences) corresponding to the Godbillon-Vey generator for W1, V ect(S ) and V ect1,0(Σ). Introduction There is a well known correspondence in homological algebra between (equivalence classes of) exact sequences Λ-modules, starting in M and ending in N with nmodules in between, and elements of ExtΛ(N,M). For Λ = U(g) the universal envelopin...