With experimental investigations and current theories, molecular modeling became an inevitable technique to study the perplexing phenomenon of glass transition. Among polymers, small variations in atomic interactions yield different values of the glass transition temperature, $T_g$. To reveal the influence of differences in the atomic functionality on the value of $T_g$, and thus to probe the molecular mechanisms responsible for this transition, atomistic simulations have to be undertaken. However, such simulations are argued not to accurately represent physically the glass transition due to the long relaxation times involved. Here we show the universality of the well-known Williams-Landel-Ferry equation for the experimental thermal dependence of polymer viscosities as demonstrated with atomistic simulations. Consequently, atomic aspects could be explicitly revealed. The contribution of atomistic simulation to the study of glass transition is thus confirmed. However, it has to be used complementarily with experiments and coarse-grained simulation to reveal the atomic aspects of current theories.

A series of spiro[pyrrolidin-2,3′-oxindoles] has been synthesized by exo-selective 1,3-dipolar cycloaddition reaction of a stabilized azomethine ylide, generated in situ by thermal [1,5]-prototropy, across various (E)-3-arylidene-1-phenyl-pyrrolidine-2,5-diones. The stereochemistry of these N-heterocycles has been confirmed using an X-ray diffraction study. To rationalize the observed regio- and stereoselectivity, DFT calculations at the B3LYP/6-31G(d,p) level were employed. It was found that this reaction preferentially affords the kinetic product. The compounds have been screened for their in vitro antibacterial, antifungal, antimalarial and antitubercular activities. Several compounds exhibited good activities comparable to those of established standard drugs.