Expert elicitation methods and a structured decision-making framework will help account for risk and uncertainty

Enzyme-powered micro/nanomotors propelled by biocompatible fuels generally show a weak propulsive force, which greatly limits their applications in complex biological environments. Herein, we have developed a novel and versatile approach to significantly enhance the propulsion of enzyme-powered micromotors by multilayered assembly of enzymes. As an example, multilayers of biotinylated ureases (BU) were asymmetrically immobilized on biotinylated Janus Au/magnetic microparticles (MMPs) with the assistance of streptavidin (SA). When the mass ratio of BU into SA and the amount of BU used in the assembly process are increased, the amount of urease immobilized on the biotinylated Janus Au/MMPs increased monotonously while the migration speed of the micromotor was augmented gradually until a saturated value. The as-optimized micromotors can be self-propelled with an average speed up to about 21.5 ± 0.8 μm/s at physiological urea concentrations (10 mM), which is five times faster than that of the monolayered counterparts and two times faster than that of the previously reported values. Owing to the enhanced thrust, the micromotors can move in liquids with viscosities similar to that of blood. In addition, with the inherent magnetic property of MMPs, the micromotors can exhibit fast magnetic separation and controllable motion direction by external magnetic fields. Our results provide a new pathway for designing high-efficient enzyme-powered micro/nanomotors and thereby promote their biomedical applications.

Policymakers make decisions about COVID-19 management in the face of considerable uncertainty. We convened multiple modeling teams to evaluate reopening strategies for a mid-sized county in the United States, in a novel process designed to fully express scientific uncertainty while reducing linguistic uncertainty and cognitive biases. For the scenarios considered, the consensus from 17 distinct models was that a second outbreak will occur within 6 months of reopening, unless schools and non-essential workplaces remain closed. Up to half the population could be infected with full workplace reopening; non-essential business closures reduced median cumulative infections by 82%. Intermediate reopening interventions identified no win-win situations; there was a trade-off between public health outcomes and duration of workplace closures. Aggregate results captured twice the uncertainty of individual models, providing a more complete expression of risk for decision-making purposes.

Summary1. Maintaining viable populations in different habitats requires physiological, morphological and demographic adaptations of plants. In sandland environments, plants experience substantial variation in growing conditions during the dune fixation process, with high sand mobility in early stages and denser vegetation cover in later stages. 2. We studied the changes in demography of a dominant shrub, Artemisia ordosica, at three stages of dune fixation: semi-fixed dunes, fixed dunes and fixed dunes covered with microbiotic crust. Demographic data from three annual censuses were used to parameterize integral projection models (IPMs) to conduct comparative demographic analyses. 3. Plant growth and reproduction decreased strongly as dunes became more fixed. Shrinkage in plant height occurred very frequently, particularly in the fixed dunes with microbiotic crust. Population growth rate (k) declined substantially with dune fixation: from rapid expansion in semi-fixed dunes (k = 1.35-1.09) to moderate decline in fixed dunes with microbiotic crust (k = 0.94-0.89). 4. Elasticity analysis revealed that survival was a key vital rate for population growth in all habitats. Growth and fecundity were of higher importance in the semi-fixed habitat than in the other two habitats where shrinkage became an important factor determining k. Seedlings and small plants were critical for population growth in semi-fixed dunes, whereas moderate to large-sized plants were most important in the other habitats. 5. Results of life table response experiments showed that the observed strong decrease in k during dune fixation was mainly caused by reduction in fecundity, but with additional and considerable contributions from reduced plant growth and increased occurrence of shrinkage. Thus, populations in semi-fixed dunes are able to expand rapidly due to a much higher fecundity compared to those in other habitats. 6. Synthesis. Artemisia ordosica adopts different life history strategies along the dune fixation process. Fast expansion in semi-fixed dunes is enabled by high seed production and effective recruitment, while populations at later dune fixation stages are maintained through frequent plant shrinkage. Integral projection models are highly appropriate tools for analysing such life history changes as they are based on statistical comparisons of vital rates across habitats.