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  1. As one of the most powerful approaches to mechanistically understanding complex chemical reaction systems and performing simulations or predictions, kinetic modeling has been widely used to investigate advanced oxidation processes (AOPs). However, most of the available models are built based on limited systems or reaction mechanisms so they cannot be readily extended to other systems or reaction conditions. To overcome such limitations, this study developed a comprehensive model on phenol oxidation with over 550 reactions, covering the most common reaction mechanisms in nine AOPs—four peroxymonosulfate (PMS), four peroxydisulfate (PDS), and one H2O2 systems—and considering the effects of co-existing anions (chloride,more »bromide, and carbonate) and product formation. Existing models in the literature were first gathered and revised by correcting inaccurately used reactions and adding other necessary reactions. Extensive model tuning and validation were then conducted by fitting the model against experimental data from both this study and the literature. When investigating the effects of anions, we found that PDS/CuO suffered the least impact, followed by the H2O2/UV and other PDS systems, and finally the PMS systems. Halogenated organic byproducts were mainly observed in the PMS systems in the presence of halides. Most of the 556 reactions were found to be important based on the sensitivity analysis, with some involving anions even among the most important, which explained why these anions can substantially alter some of the reaction systems. With this comprehensive model, a deep understanding and reliable prediction can be made for the oxidation of phenol (and likely other phenolic compounds) in systems containing one or more of the above AOPs.« less
    Free, publicly-accessible full text available November 30, 2022
  2. The effect of thermal treatment at 220 °C for 10 days on the structure and transport properties of a triptycene-based polybenzoxazole (TPBO) was investigated experimentally and theoretically. Gas and water vapor sorption in TPBO is virtually unaffected by thermal treatment, while diffusion and permeability coefficients decrease by just 20%. Remarkably, the CO2/CH4 selectivity exhibit a negligible change. Fluorescence spectroscopy, WAXD and FTIR analysis indicate that, in sharp contrast with typical behavior of glassy polymers, TPBO does not experience accelerated physical aging, and rule out formation of intermolecular charge transfer complexes upon thermal treatment. According with this physical picture, the diffusion coefficientmore »of penetrant molecules sorbed in the Langmuir's mode, DH, does not change after treatment. Small molecule diffusivity and permeability decline is caused by a decrease in polymer chain mobility, which makes more difficult opening gaps to allow penetrant diffusion jumps. According to this picture, the Henry's mode diffusion coefficient, DD, substantially decreases upon thermal treatment. The higher stability exhibited by TPBO relative to other high Tg glassy polymers is ascribed to the presence of configurational free volume, which is not related to the non-equilibrium transient conformation, but to the molecular configuration and, as such, it is not relaxed upon protracted exposure to high temperatures.« less
  3. Abstract The cosmic web contains filamentary structure on a wide range of scales. On the largest scales, superclustering aligns multiple galaxy clusters along intercluster bridges, visible through their thermal Sunyaev–Zel’dovich signal in the cosmic microwave background. We demonstrate a new, flexible method to analyze the hot gas signal from multiscale extended structures. We use a Compton y -map from the Atacama Cosmology Telescope (ACT) stacked on redMaPPer cluster positions from the optical Dark Energy Survey (DES). Cutout images from the y -map are oriented with large-scale structure information from DES galaxy data such that the superclustering signal is aligned beforemore »being overlaid. We find evidence of an extended quadrupole moment of the stacked y signal at the 3.5 σ level, demonstrating that the large-scale thermal energy surrounding galaxy clusters is anisotropically distributed. We compare our ACT × DES results with the Buzzard simulations, finding broad agreement. Using simulations, we highlight the promise of this novel technique for constraining the evolution of anisotropic, non-Gaussian structure using future combinations of microwave and optical surveys.« less
    Free, publicly-accessible full text available July 1, 2023