Extracellular DNA (eDNA) is an important polymeric substance that plays essential roles in cell aggregation and nutrient provision for the sessile bacteria. eDNA in bacterial biofilms was extensively studied. Here we found that eDNA also exists in symplasmata, a bacterial cell aggregate, which is different to a biofilm, in the rice enophyte Pantoea agglomerans YS19. We found that exogenous eDNA enhanced the formation and stability of symplasmata significantly, and that, exogenous eDNA also improved the stress resistance and colonization ability of the bacterium on host rice. These results strongly indicate novel roles of the eDNA in Pantoea agglomerans YS19, showing its special relation to the stress-resistance and endophyte-host association of the strain.

Due to the narrow operating range with the high efficiency of Wells turbines, the performance of Oscillating Water Column (OWC) systems is extremely limited by the stall issue. In this study, a detailed investigation on the flow physics at three typical flow rates corresponding to the design, stall inception, and deep stall conditions is performed, aiming to explore the mechanisms governing the evolution of the leading-edge vortex in terms of the circulation budget analysis. For this purpose, 3D unsteady Reynolds-averaged Navier-Stokes equations with the shear-stress-transport turbulence model are solved for a monoplane Wells turbine with high solidity under the steady-state inflow conditions. The numerical results show encouraging agreement with the available experimental data. The transient flow behaviors of stall inception and deep stall mode are captured by the Proper Orthogonal Decomposition (POD) method. Furthermore, the contributions of the spanwise convection of the vorticity gradient, vorticity tilting term, and the shear layer flux to the circulation of the leading-edge vortex are quantitatively determined within the spanwise control surface. The results indicate that, for stall inception condition, the high turbulent kinetic energy regions are attached to the leading edge of the suction surface with a disturbance of 0.33 times of the rotor frequency. The leading-edge vortex appears after the turbine stall, and its stable development time is less than 1/4 of the rotor period. Although leading-edge vortex occurs periodically after the first shedding with a significant decrease of circulation, it is almost not reattached to the blade surface, which speeds up the shedding and vorticity dissipation. The first shedding of the leading-edge vortex is related to the increase of radial vorticity gradient, but not directly related to the radial velocity. Furthermore, the spatiotemporal distribution of the circulation is similar to the spanwise convection, but there is a phase difference. In addition, the tilting term changes greatly in the evolution of the leading-edge vortex, indicating that the tangential and axial vorticity are tilted, which is verified by the spatial streamlines.

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Summary A combined power conversion system, which consists of a supercritical carbon dioxide recompression cycle with an organic Rankine cycle as the bottoming cycle, has broad potential for maritime propulsion applications. However, the performance of the combined system under the off‐design condition and operating states of compressors with a wide range of load variations and different control strategies have not been comprehensively investigated. Therefore, a simulation model for the combined system under off‐design conditions is established in the present study to investigate the compressors operating states and the performance of the system under different control strategies. The result shows that a peak efficiency of 42.82% and total production unit cost of 11.6 $/GJ are achieved at the design point for the combined system, where the pressure ratio, flow split ratio, and evaporating pressure are 2.7, 0.27, and 770 kPa, respectively. When the relative load varies from 100% to 10%, the efficiency of the inventory‐controlled system decreases by 19.07%, and the efficiency of the bypass‐controlled system decreases by 34.3%. For the 10% load scenario, the compressors tend to surge under the inventory‐controlled strategy and approach the choke area under the bypass‐controlled strategy. The adoption of the inventory‐bypass hybrid control strategy keeps the compressors of the low‐load system away from the surge and choke areas, and the efficiency is between those of the systems controlled by the two separate strategies.