Entrainment by axisymmetric jets impinging on a flat plate

An experimental technique is described for the determination of the entrainment in an axisymmetric gaseous jet impinging normally on a flat plate situated below the nozzle. Typical results are given of experimental work carried out using this technique for an Rix jet flowing into a like atmosphere of similar density. These results suggest that the relationships describing the entrainment are: (a) m/mo = 0.3 hid for the axial jet, and (b) mimo = 0.6 Rid for the wall jet. It is also deduced that the growth of the *wall jet is described by the equation: 5 w r approximately. Some experimental results are given for a jet at a higher temperature than the surrounding atmosphere

Spatiotemporal distribution and abundance of mangrove ecosystem engineers: burrowing crabs around canopy gaps

The burrowing and feeding activities of fiddler and sesarmid crabs have considerable impacts on ecosystem functioning, accordingly they are considered ecosystem engineers. Identifying the factors influencing spatial and temporal variability in crab distribution and abundance would allow us to make predictions of their engineering impacts over a variety of habitats, which is essential for understanding the functionality of mangrove ecosystems. Here we determined the spatial and temporal distributions and abundances of fiddler crabs and sesarmids around canopy gaps in the mangroves of Darwin Harbour, Australia. We sampled three microhabitats at each canopy gap (site): gap center, gap edge and forest edge. We counted crabs and measured selected environmental variables at thirty sites stratified by height within two creek systems during a single season and at six sites within one creek system over two years. Fiddler crabs were generally more abundant in gap centers with Uca flammula preferring lower sites than Uca elegans or Uca signata, while sesarmids favored low to mid-height vegetated sites. Canonical Correspondence analyses showed spatial abundances to be partitioned and the main driving factors were canopy density and site height, as well as substrate features (sediment mounds, soil moisture, soil penetrability, soil surface temperature). Temporal abundances were either highly variable (U. signata) or showed significant seasonal variation only at exposed (U. flammula) or higher (U. elegans) sites. The main factors driving temporal partitioning were humidity, wind speed, sunshine, and soil and air temperatures. Our results indicate that the distribution and abundance of crabs in mangroves varies over time and space, and with sampling scale. Substrate and environmental variables had been largely overlooked by previous studies describing the distribution and abundance of mangrove crabs. We, accordingly, suggest that studies designed to understand mangrove functionality include fine-grained spatial and temporal assessments of ecosystem engineers

Concerted functions of<i> Streptococcus gordonii</i> surface proteins PadA and Hsa mediate activation of human platelets and interactions with extracellular matrix

A range of Streptococcus bacteria are able to interact with blood platelets to form a thrombus (clot). Streptococcus gordonii is ubiquitous within the human oral cavity and amongst the common pathogens isolated from subjects with infective endocarditis. Two cell surface proteins, Hsa and Platelet adherence protein A (PadA), in S. gordonii mediate adherence and activation of platelets. In this study, we demonstrate that PadA binds activated platelets and that an NGR (Asparagine-Glycine-Arginine) motif within a 657 amino acid residue N-terminal fragment of PadA is responsible for this, together with two other integrin-like recognition motifs RGT and AGD. PadA also acts in concert with Hsa to mediate binding of S. gordonii to cellular fibronectin and vitronectin, and to promote formation of biofilms. Evidence is presented that PadA and Hsa are each reliant on the other\u27s active presentation on the bacterial cell surface, suggesting cooperativity in functions impacting both colonization and pathogenesis

O-mannosylation in Candida albicans enables development of interkingdom biofilm communities

Peer reviewedPublisher PD