Free Wave Propagation in Plates of General Anisotropic Media

The propagation of Lamb waves in plates has been the subject of numerous investigations since their postulation by Lamb in 1916 [1,2]. Most of the work in existence deals with various aspects of these guided waves in plates of isotropic materials. Comparatively speaking a limited number of results has appeared in which Lamb or horizontaly polarized SH wave propagation in anisotropic plates has been considered in any detail. For Lamb waves, theoretical analyses have been reported in plates of cubic [3,4], transversely isotropic [5,6], and orthotropic [7,9] media

Structural and mechanistic determinants of c-di-GMP signalling

Bis-(3'-5' -cyclic dimeric GMP (c-di-GMP) is a ubiquito us second messenger that regulates cell surface-associated traits in bacteria. Components of this regulatory network include GGDEF and EAL domain-containing proteins that det ermine the cellular concentrations of c-di-GMP by mediatin g its synthesis and degradation, respectively. Crystal str ucture analyses in combination with functional studies have revealed the catalytic mechanisms and regulatory princip les involved. Downstream, c-di-GMP is recognized by PilZ d omain-containing receptors that can undergo large-scale do main rearrangements on ligand binding. Here, we review rec ent data on the structure and functional properties of the protein families that are involved in c-di-GMP signalling and discuss the mechanistic implications