In this paper, we detail the geometrical approach of small cancellation theory used by Delzant and Gromov to provide a new proof of the infiniteness of free Burnside groups and periodic quotients of torsion-free hyperbolic groups.

This article reports an assessment of the global warming potential associated with the life cycle of a biopolymer (poly(hydroxyalkanoate) or PHA) produced in genetically engineered corn developed by Monsanto. The grain corn is harvested in a conventional manner, and the polymer is extracted from the corn stover (i.e., residues such as stalks, leaves and cobs), which would be otherwise left on the field. While corn farming was assessed based on current practice, four different hypothetical PHA production scenarios were tested for the extraction process. Each scenario differed in the energy source used for polymer extraction and compounding, and the results were compared to polyethylene (PE). The first scenario involved burning of the residual biomass (primarily cellulose) remaining after the polymer was extracted from the stover. In the three other scenarios, the use of conventional energy sources of coal, oil, and natural gas were investigated. This study indicates that an integrated system, wherein biomass energy from corn stover provides energy for polymer processing, would result in a better greenhouse gas profile for PHA than for PE. However, plant‐based PHA production using fossil fuel sources provides no greenhouse gas advantage over PE, in fact scoring worse than PE. These results are based on a “cradle‐to‐pellet” modeling as the PHA end‐of‐life was not quantitatively studied due to complex issues surrounding the actual fate of postconsumer PHA.

In this article, we construct partial periodic quotients of groups which have a non-elementary acylindrical action on a hyperbolic space. In particular, we provide infinite quotients of mapping class groups where a fixed power of every pseudo-Anosov homeomorphism is identified with a periodic or reducible element.

Abstract. Using small cancellation for rotation families of groups, we construct new examples of aspherical polyhedra.

No abstract