Dissipative Structures in Supersonic Turbulence

We show that density-weighted moments of the dissipation rate, $\epsilon_l$, averaged over a scale $l$, in supersonic turbulence can be successfully explained by the She and L\'ev\^eque model [Phys. Rev. Lett. {\bf 72}, 336 (1994)]. A general method is developed to measure the two parameters of the model, $\gamma$ and $d$, based directly on their physical interpretations as the scaling exponent of the dissipation rate in the most intermittent structures ($\gamma$) and the dimension of the structures ($d$). We find that the best-fit parameters ($\gamma=0.71$ and $d=1.90$) derived from the $\epsilon_l$ scalings in a simulation of supersonic turbulence at Mach 6 agree with their direct measurements, confirming the validity of the model in supersonic turbulence.Comment: 4 pages, 3 figures, accepted by Phys. Rev. Let

Fine-Tuning Covalent Inhibition of Bacterial Quorum Sensing

Emerging antibiotic resistance among human pathogens has galvanized efforts to find alternative routes to combat bacterial virulence. One new approach entails interfering with the ability of bacteria to coordinate population‐wide gene expression, or quorum sensing (QS), thus inhibiting the production of virulence factors and biofilm formation. We have recently developed such a strategy by targeting LasR, the master regulator of QS in the opportunistic human pathogen Pseudomonas aeruginosa, through the rational design of covalent inhibitors closely based on the core structure of the native ligand. We now report several groups of new inhibitors, one of which, fluoro‐substituted ITC‐12, displayed complete covalent modification of LasR, as well as effective QS inhibition in vitro and promising in vivo results. In addition to their potential clinical relevance, this series of synthetic QS modulators can be used as a tool to further unravel the complicated QS regulation in P. aeruginosa