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Few studies have explored the effects of fine particulate matter (PM2.5) and its constituents on the progression of cerebral blood flow velocity (BFV) and the potential modifying role of greenness. In this study, we investigated the association of PM2.5 and its constituents, including sulfate (SO42−), nitrate (NO3−), ammonium (NH4+), organic matter (OM), and black carbon (BC), with the progression of BFV in the middle cerebral artery. Participants from the Beijing Health Management Cohort who underwent at least two transcranial Doppler sonography examinations during 2015–2020 were recruited. BFV change and BFV change rate were used to define the progression of cerebral BFV. Linear mixed effects models were employed to analyze the data, and the weighted quantile sum regression assessed the contribution of PM2.5 constituents. Additionally, greenness was examined as a modifier. Among the examined constituents, OM exhibited the strongest association with BFV progression. An interquartile range increase in PM2.5 and OM exposure concentrations was associated with a decrease of −16.519 cm/s (95% CI: −17.837, −15.201) and −15.403 cm/s (95% CI: −16.681, −14.126) in BFV change, and −10.369 cm/s/year (95% CI: −11.387, −9.352) and −9.615 cm/s/year (95% CI: −10.599, −8.632) in BFV change rate, respectively. Furthermore, stronger associations between PM2.5 and BFV progression were observed in individuals working in areas with lower greenness, those aged under 45 years, and females. In conclusion, reducing PM2.5 levels in the air, particularly the OM constituent, and enhancing greenness could potentially contribute to the protection of cerebrovascular health. Plain Language Summary: Fine particulate matter in the atmosphere has been shown to be associated with cerebrovascular disease, however, the adverse effects of fine particulate matter chemical constituents on cerebral hemodynamics and the role of greenness in this are yet to be evaluated. In this study, we evaluated the association of fine particulate matter and its constituents (sulfate, nitrate, ammonium, black carbon, and organic matter) with cerebral arterial blood flow velocity (BFV) and the modifying effect of greenness. We found that fine particulate matter and its constituents accelerate the reduction of cerebral arterial BFV and that the association is stronger where greenness levels are low. Our findings provide new evidence that reducing fine particle exposure and enhancing urban greenery may be an effective way to protect cerebrovascular health. Key Points: PM2.5 and its constituents were associated with a greater and faster reduction in the cerebral artery blood flow velocityThe impacts of PM2.5 and its constituents were modified by greennessYounger people and females were found to be more vulnerable [ABSTRACT FROM AUTHOR]

Mass transfer characteristics in a rotor-stator reactor in terms of the overall volumetric mass-transfer coefficient ( Kxa) using the N2-H2O-O2 system were investigated. The effects of various operating parameters including rotation speed, liquid volumetric flow rate, and gas volumetric flow rate on Kxa were systematically examined, and a gas-liquid mass transfer model was established to predict Kxa. Results reveal that Kxa increased with higher rotation speed, liquid volumetric flow rate, and gas volumetric flow rate. The results also confirm that the predicted values of Kxa were in agreement with the experimental values with deviation within 15 %. The results contribute to a better understanding of mass transfer characteristics in rotor-stator reactors. [ABSTRACT FROM AUTHOR]