An asymptotic strategy to couple homogenized elastic structures

A two-scale methodology to calculate the local stress-strain state (SSS) in structures composed of connected elements is proposed. The methodology is based on the assumption that the connecting unit has a size small in comparison to the objects being connected. It is demonstrated that the problem of connection allows asymptotic decomposition. At the macroscopic level (the zero order approximation), an interface problem, with appropriate interface conditions, is revealed. At this order, the individual properties of the joint are neglected. These properties manifest themselves at the next asymptotic order, which takes into account all individual joint properties using the solution of the macroscopic problem. The local SSS in the vicinity of joint consists of the SSS in the connecting unit, together with rapidly decaying boundary layers in the connected elements. A detail elucidation of the local SSS in the connecting unit is an important distinction of this work from previous studies of connected structures. Motivated by the asymptotic analysis, a numerical method for simultaneously calculating the SSS in both the connected structures and the connecting unit is developed. An illustrative example, involving computation of the SSS in the vicinity of an explosion welding seam, is presented

The Yersinia Ysc-Yop 'type III' weaponry

'Type III secretion'--the mechanism by which some pathogenic bacteria inject proteins straight into the cytosol of eukaryotic cells to 'anaesthetize' or 'enslave' them--was discovered in 1994. Important progress has been made in this area during the past few years: the bacterial organelles responsible for this secretion--called 'injectisomes'--have been visualized, the structures of some of the bacterial protein 'effectors' have been determined, and considerable progress has been made in understanding the intracellular action of the effectors. Type III secretion is key to the pathogenesis of bacteria from the Yersinia genus