Browsing by Author "Xu, Lu"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Coupling of organic and inorganic aerosol systems and the effect on gas-particle partitioning in the southeastern US
    Pye, Havala O. T.; Zuend, Andreas; Fry, Juliane L.; Isaacman-VanWertz, Gabriel; Capps, Shannon L.; Appel, K. Wyat; Foroutan, Hosein; Xu, Lu; Ng, Nga L.; Goldstein, Allen H. (European Geophysical Union, 2018-01-12)
    Several models were used to describe the partitioning of ammonia, water, and organic compounds between the gas and particle phases for conditions in the southeastern US during summer 2013. Existing equilibrium models and frameworks were found to be sufficient, although additional improvements in terms of estimating pure-species vapor pressures are needed. Thermodynamic model predictions were consistent, to first order, with a molar ratio of ammonium to sulfate of approximately 1.6 to 1.8 (ratio of ammonium to 2 x sulfate, R-N/2S approximate to 0.8 to 0.9) with approximately 70% of total ammonia and ammonium (NHx) in the particle. Southeastern Aerosol Research and Characterization Network (SEARCH) gas and aerosol and Southern Oxidant and Aerosol Study (SOAS) Monitor for AeRosols and Gases in Ambient air (MARGA) aerosol measurements were consistent with these conditions. CMAQv5.2 regional chemical transport model predictions did not reflect these conditions due to a factor of 3 overestimate of the nonvolatile cations. In addition, gas-phase ammonia was overestimated in the CMAQ model leading to an even lower fraction of total ammonia in the particle. Chemical Speciation Network (CSN) and aerosol mass spectrometer (AMS) measurements indicated less ammonium per sulfate than SEARCH and MARGA measurements and were inconsistent with thermodynamic model predictions. Organic compounds were predicted to be present to some extent in the same phase as inorganic constituents, modifying their activity and resulting in a decrease in [H+](air) (H+ in mu g m(-3) air), increase in ammonia partitioning to the gas phase, and increase in pH compared to complete organic vs. inorganic liquid-liquid phase separation. In addition, accounting for nonideal mixing modified the pH such that a fully interactive inorganic-organic system had a pH roughly 0.7 units higher than predicted using traditional methods (pH = 1.5 vs. 0.7). Particle-phase interactions of organic and inorganic compounds were found to increase partitioning towards the particle phase (vs. gas phase) for highly oxygenated (O : C >= 0.6) compounds including several isoprene-derived tracers as well as levoglucosan but decrease particle-phase partitioning for low O : C, monoterpene-derived species.
  • Thumbnail Image
    Tetrahydrocurcumin protects against nonalcoholic fatty liver disease by improving lipid metabolism and redox homeostasis
    Gao, Feng; Chen, Manyu; Yu, Jianfeng; Xu, Lu; Yu, Lisha; Jiang, Honglin; Gu, Zhiliang (Elsevier, 2022-02)
    Nonalcoholic fatty liver disease (NAFLD) is the most common liver metabolic disease in the world. In this study we investigated the effect of tetrahydrocurcumin (THC), a potent antioxidant, on NAFLD. We found that THC significantly reduced the body weight, serum and liver lipids, serum malondialdehyde (MDA) and fasting blood glucose (FBG) of male NAFLD mice induced by feeding a high-fat diet (HFD) for 8 weeks. A RNA-seq analysis revealed that THC also affected the expression of many genes involved in lipid metabolism in the liver of NAFLD mice, including increasing the mRNA expression of CYP51 and FOXQ1. Moreover, THC significantly reduced sodium oleate-induced lipid accumulation, activated the NRF2 pathway, and up-regulated the mRNA expression of FGF21 in HepG2 cells. Overall, our study showed that THC can improve the antioxidant capacity of liver, which suggests that dietary THC may be used to treat NAFLD.