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Abstract Active emulsions and liquid crystalline shells are intriguing and experimentally realisable types of topological matter. Here we numerically study the morphology and spatiotemporal dynamics of a double emulsion, where one or two passive small droplets are embedded in a larger active droplet. We find activity introduces a variety of rich and nontrivial nonequilibrium states in the system. First, a double emulsion with a single active droplet becomes self-motile, and there is a transition between translational and rotational motion: both of these regimes remain defect-free, hence topologically trivial. Second, a pair of particles nucleate one or more disclination loops, with conformational dynamics resembling a rotor or chaotic oscillator, accessed by tuning activity. In the first state a single, topologically charged, disclination loop powers the rotation. In the latter state, this disclination stretches and writhes in 3D, continuously undergoing recombination to yield an example of an active living polymer. These emulsions can be self-assembled in the lab, and provide a pathway to form flow and topological patterns in active matter in a controlled way, as opposed to bulk systems that typically yield active turbulence.

Evolution of the SARS-CoV-2 spike protein is likely driven by many factors, including immune escape and receptor binding. Here, by measuring the binding affinity of more than 30,000 variants of the SARS-CoV-2 RBD to its receptor ACE2, Moulana et al. show that the evolution of the Omicron BA.1 variant was driven by interactions between mutations.

Active emulsions and liquid crystalline shells are intriguing and experimentally realisable types of topological matter. Here we numerically study the morphology and spatiotemporal dynamics of a double emulsion, where one or two passive small droplets are embedded in a larger active droplet. We find activity introduces a variety of rich and nontrivial nonequilibrium states in the system. First, a double emulsion with a single active droplet becomes self-motile, and there is a transition between translational and rotational motion: both of these regimes remain defect-free, hence topologically trivial. Second, a pair of particles nucleate one or more disclination loops, with conformational dynamics resembling a rotor or chaotic oscillator, accessed by tuning activity. In the first state a single, topologically charged, disclination loop powers the rotation. In the latter state, this disclination stretches and writhes in 3D, continuously undergoing recombination to yield an example of an active living polymer. These emulsions can be self-assembled in the lab, and provide a pathway to form flow and topological patterns in active matter in a controlled way, as opposed to bulk systems that typically yield active turbulence. Active emulsions and liquid crystalline shells offer a unique framework for exploring topological matter due to their complex morphologies and dynamic properties. Here the authors report how activity generates diverse nonequilibrium states, from defect-free motile states to complex topologically active configurations, providing insights into controlled flow and topology in active systems. [ABSTRACT FROM AUTHOR]

Emerging SARS-CoV-2 mutants may escape neutralization by antibodies. Here, the authors use deep mutational scanning to identify mutations in the RBD that escape human monoclonal antibodies or convalescent plasmas.

Bacteria continuously inject energy into their surroundings and thus induce chaotic like flows, namely meso-scale turbulence. Here, the authors show that transition to meso-scale turbulence and inertial turbulence observed in pipes share the same scaling behavior that belongs to the directed percolation universality class.