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We compiled a data set of the compounds that terrestrial vertebrates (amniotes) use to send chemical signals, and searched for relationships between signal compound properties and signal function. Overall, relationships were scarce and formed only small-scale patterns. Terrestrial vertebrate signalling compounds are invariably components of complex mixtures of compounds with diverse molecular weights and functionalities. Signal compounds with high molecular weights (MWs) and low vapour pressures, or that are bound to carrier proteins, are detected during direct contact with the source of the signal. Stable compounds with aromatic rings in their structures are more common in signals of social dominance, including territoriality. Aldehydes are emitted from the sender's body rather than from scent marks. Lipocalin pheromones and carriers have a limited range of MWs, possibly to reduce the metabolic costs of their biosynthesis. Design constraints that might channel signal chemistry into patterns have been relaxed by amniote behavior and biochemistry. Amniote olfaction has such a high sensitivity, wide range and narrow resolution that signal detection imposes no practical constraints on the structures of signalling molecules. Diverse metabolic pathways in amniotes and their microbial commensals produce a wide variety of compounds as chemical signals and as matrix compounds that free signal components from the constraints of stability, vapor pressure, species-specificity etc. that would otherwise constrain what types of compound operate optimally under different conditions.

The effect of fine dispersoids on the mechanisms and rate of grain refinement has been investigated during the severe deformation of a model aluminium alloy. A binary Al-0.2Sc alloy, containing coherent Al 3 Sc dispersoids, of $20 nm in diameter and $100 nm spacing, has been deformed by equal channel angular extrusion to an effective strain of ten. The resulting deformation structures were quantitatively analysed using high-resolution electron backscattered diffraction orientation mapping, and the results have been compared to those obtained from a single-phase Al-0.13Mg alloy, deformed under identical conditions. The presence of fine, nonshearable, dispersoids has been found to homogenise slip, retard the formation of a cellular substructure and inhibit the formation of microshear bands during deformation. These factors combine to reduce the rate of high-angle grain boundary generation at low to medium strains and, hence, retard the formation of a submicron grain structure to higher strains during severe deformation.