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Journal article(2025)
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Anran Ren, Mingchen Yao, Yue Zhang, Lihua Chen, Xiaoming Li, Wei Yan, Walter van der Meer, Joan Rose, Gang Liu
Shower systems create conditions conducive to the growth of opportunistic pathogens, but the timing and location of associated risks are poorly understood. In this study, we constructed 48 full size shower units with six incubation periods (4, 10, 16, 22, 30, and 40 weeks) and four water heater temperature (39, 45, 51, and 58 °C) to examine the dynamics of microbial growth and pathogen distribution. Results showed that during the initial stage (4 weeks), peak biomass was observed for all biofilms, ranked as shower hose (SHE) > cold-water pipe (CWP) > hot-water pipe (HWP), followed by a sharp decline by the 10th-week. At the 4th-week, the biofilm was loose and easily detached into the water, possibly promoted by leached organic carbon from plastic material, fostering the growth of specific microorganisms. The impacts of stagnation and temperature became more pronounced in CWP and HWP over time. Legionella pneumophila appeared in biofilms at the 4th-week, disappeared, and reappeared in large numbers since the 22nd-week. Differently, Mycobacterium spp. emerged in large numbers after 30 weeks. Both pathogens were notably enriched in showerheads and shower hoses. This study highlights critical periods of higher risk in shower systems, particularly in the early stages (4 weeks) and after 22 weeks, suggesting that risks can be mitigated by pre-soaking pipes or regularly cleaning (e.g., heat shock flushing) and replacing showerheads and hoses.
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Shower systems create conditions conducive to the growth of opportunistic pathogens, but the timing and location of associated risks are poorly understood. In this study, we constructed 48 full size shower units with six incubation periods (4, 10, 16, 22, 30, and 40 weeks) and four water heater temperature (39, 45, 51, and 58 °C) to examine the dynamics of microbial growth and pathogen distribution. Results showed that during the initial stage (4 weeks), peak biomass was observed for all biofilms, ranked as shower hose (SHE) > cold-water pipe (CWP) > hot-water pipe (HWP), followed by a sharp decline by the 10th-week. At the 4th-week, the biofilm was loose and easily detached into the water, possibly promoted by leached organic carbon from plastic material, fostering the growth of specific microorganisms. The impacts of stagnation and temperature became more pronounced in CWP and HWP over time. Legionella pneumophila appeared in biofilms at the 4th-week, disappeared, and reappeared in large numbers since the 22nd-week. Differently, Mycobacterium spp. emerged in large numbers after 30 weeks. Both pathogens were notably enriched in showerheads and shower hoses. This study highlights critical periods of higher risk in shower systems, particularly in the early stages (4 weeks) and after 22 weeks, suggesting that risks can be mitigated by pre-soaking pipes or regularly cleaning (e.g., heat shock flushing) and replacing showerheads and hoses.
Journal article(2025)
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Bowen Shi, Tianyi Zeng, Nairong Tao, Xianbo Shi, Jiarong Zhang, Wei Wang, Sybrand van der Zwaag, Yiyin Shan, Wei Yan
A novel oxide-dispersed strengthened T250 maraging steel (ODS-T250 steel) was prepared by mechanical ball milling followed by hot isostatic pressing. Martensitic transformation behavior, ultrafine-grained martensite microstructure and tensile properties of the ODS-T250 steel were compared to its oxide-free counterpart (T250 steel). The results indicated that ODS-T250 steel exhibited excellent microstructural thermal stability, maintaining an effective grain size of 0.348 μm even after quenching from 1200 °C, whereas T250 steel exhibited a much larger grain size of 5.473 μm. After quenching, the ODS-T250 steel showed significantly distinct variant selectivity, and its martensite morphology was unprecedented equiaxed structure rather than typical lath-type. Statistical analysis revealed that there was only a single variant formed when the prior austenite grain size (PAGS) was below 0.43 μm. Moreover, the martensite start (Ms) temperature of ODS-T250 steel was lower than the T250 steel due to its ultrafine PAGS and the dispersed oxide particles. The refinement of PAGS and the presence of oxide particles led to a simultaneous improvement in both strength and ductility of ODS-T250 steel.
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A novel oxide-dispersed strengthened T250 maraging steel (ODS-T250 steel) was prepared by mechanical ball milling followed by hot isostatic pressing. Martensitic transformation behavior, ultrafine-grained martensite microstructure and tensile properties of the ODS-T250 steel were compared to its oxide-free counterpart (T250 steel). The results indicated that ODS-T250 steel exhibited excellent microstructural thermal stability, maintaining an effective grain size of 0.348 μm even after quenching from 1200 °C, whereas T250 steel exhibited a much larger grain size of 5.473 μm. After quenching, the ODS-T250 steel showed significantly distinct variant selectivity, and its martensite morphology was unprecedented equiaxed structure rather than typical lath-type. Statistical analysis revealed that there was only a single variant formed when the prior austenite grain size (PAGS) was below 0.43 μm. Moreover, the martensite start (Ms) temperature of ODS-T250 steel was lower than the T250 steel due to its ultrafine PAGS and the dispersed oxide particles. The refinement of PAGS and the presence of oxide particles led to a simultaneous improvement in both strength and ductility of ODS-T250 steel.
