科研成果

The effects of flagella and their properties on bacterial transport and deposition behaviors were examined by using four types of Escherichia coli (E. coli) with or without flagella, as well as with normal or sticky flagella. Packed column, quartz crystal microbalance with dissipation, visible parallel-plate flow chamber system, and visible flow chamber packed with porous media system were employed to investigate the deposition mechanisms of bacteria with different properties of flagella. We found that the presence of flagella favored E. coli deposition onto quartz sand/silica surfaces. Moreover, by changing the porous media porosity and directly observing the bacterial deposition process, local sites with high roughness, narrow flow channels, and grain-to-grain contacts were found to be the major sites for bacterial deposition. Particularly, flagella could help bacteria swim near and then deposit at these sites. In addition, we found that due to the stronger adhesive forces, sticky flagella could further enhance bacterial deposition onto quartz sand/silica surfaces. Elution experiments indicated that flagella could help bacteria attach onto sand surfaces more irreversibly. Clearly, flagella and their properties would have obvious impacts on the transport/deposition behaviors of bacteria in porous media. © 2021 American Chemical Society.

When using spectral methods, a consistent method for tuning the expansion order is often required, especially for time-dependent problems in which oscillations emerge in the solution. In this paper, we propose a frequency-dependent p-adaptive technique that adaptively adjusts the expansion order based on a frequency indicator. Using this p-adaptive technique, combined with recently proposed scaling and moving techniques, we are able to devise an adaptive spectral method in unbounded domains that can capture and handle diffusion, advection, and oscillations. As an application, we use this adaptive spectral method to numerically solve Schrödinger’s equation in an unbounded domain and successfully capture the solution’s oscillatory behavior at infinity.