Pore-Scale Investigation of Coupled Two-Phase and Reactive Transport in the Cathode Electrode of Proton Exchange Membrane Fuel Cells

A three-dimensional multicomponent multiphase lattice Boltzmann model(LBM)is established to model the coupled two-phase and reactive transport phenomena in the cathode electrode of proton exchange membrane fuel cells.The gas diff usion layer(GDL)and microporous layer(MPL)are stochastically reconstructed with the inside dynamic distribution of oxygen and liquid water resolved,and the catalyst layer is simplifi ed as a superthin layer to address the electrochemical reaction,which provides a clear description of the fl ooding eff ect on mass transport and performance.Diff erent kinds of electrodes are reconstructed to determine the optimum porosity and structure design of the GDL and MPL by comparing the transport resistance and per-formance under the fl ooding condition.The simulation results show that gradient porosity GDL helps to increase the reactive area and average concentration under fl ooding.The presence of the MPL ensures the oxygen transport space and reaction area because liquid water cannot transport through micropores.Moreover,the MPL helps in the uniform distribution of oxygen for an effi cient in-plane transport capacity.Crack and perforation structures can accelerate the water transport in the assembly.The systematic perforation design yields the best performance under fl ooding by separating the transport of liquid water and oxygen.

Functional Metabolomics Reveals that Astragalus Polysaccharides Improve Lipids Metabolism through Microbial Metabolite 2-Hydroxybutyric Acid in Obese Mice

Polysaccharides are widely present in herbs with multiple activities,especially immunity regulation and metabolic benefits for metabolic disorders.However,the underlying mechanisms are not well under-stood.Functional metabolomics is increasingly used to investigate systemic effects on the host by iden-tifying metabolites with particular functions.This study explores the mechanisms underlying the metabolic benefits of Astragalus polysaccharides(APS)by adopting a functional metabolomics strategy.The effects of APS were determined in eight-week high-fat diet(HFD)-fed obese mice.Then,gas chromatography–time-of-flight mass spectrometry(GC–TOFMS)-based untargeted metabolomics was performed for an analysis of serum and liver tissues,and liquid chromatography–tandem mass spectrom-etry(LC–MS/MS)-based targeted metabolomics was performed.The potential functions of the metabo-lites were tested with in vitro and in vivo models of metabolic disorders.Our results first confirmed the metabolic benefits of APS in obese mice.Then,metabolomics analysis revealed that APS supplemen-tation reversed the HFD-induced metabolic changes,and identified 2-hydroxybutyric acid(2-HB)as a potential functional metabolite for APS activity that was significantly decreased by a HFD and reversed by APS.Further study indicated that 2-HB inhibited oleic acid(OA)-induced triglyceride(TG)accumula-tion.It was also found to stimulate the expression of proteins in lipid degradation in hepatocytes and TG lipolysis in 3T3-L1 cells.Moreover,it was found to reduce serum TG and regulate the proteins involved in lipid degradation in high-fat and high-sucrose(HFHS)-fed mice.In conclusion,our study demonstrates that the metabolic benefits of APS are at least partially due to 2-HB generation,which modulated lipid metabolism both in vitro and in vivo.Our results also highlight that functional metabolomics is practical for investigating the mechanism underlying the systemic benefits of plant polysaccharides.