15 research outputs found
Enhanced daytime secondary aerosol formation driven by gas-particle partitioning in downwind urban plumes
Anthropogenic emissions from city clusters can significantly enhance secondary organic aerosol (SOA) formation in the downwind regions, while the mechanism is poorly understood. To investigate the effect of pollutants within urban plumes on organic aerosol (OA) evolution, a field campaign was conducted at a downwind site of the Pearl River Delta region of China in the fall of 2019. A time-of-flight chemical ionization mass spectrometer coupled with a Filter Inlet for Gases and Aerosol (FIGAERO-CIMS) was used to probe the gas- and particle-phase molecular composition and thermograms of organic compounds. For air masses influenced by urban pollution, strong daytime SOA formation through gas-particle partitioning was observed, resulting in higher OA volatility. The obvious SOA enhancement was mainly attributed to the equilibrium partitioning of non-condensable (C * ≥ 100.5 μg m-3) organic vapors. We speculated that the elevated NOx concentration could suppress the formation of highly oxidized products, resulting in a smooth increase of condensable (C * < 100.5 μg m-3) organic vapors. Evidence showed that urban pollutants (NOx and VOCs) could enhance the oxidizing capacity, while the elevated VOCs was mainly responsible for promoting daytime SOA formation by increasing the RO2 production rate. Our results highlight the important role of urban anthropogenic pollutants in SOA control in the suburban region
Kartogenin (KGN)/synthetic melanin nanoparticles (SMNP) loaded theranostic hydrogel scaffold system for multiparametric magnetic resonance imaging guided cartilage regeneration
Abstract Cartilage regeneration after injury is still a great challenge in clinics, which suffers from its avascularity and poor proliferative ability. Herein we designed a novel biocompatible cellulose nanocrystal/GelMA (gelatin‐methacrylate anhydride)/HAMA (hyaluronic acid‐methacrylate anhydride)‐blended hydrogel scaffold system, loaded with synthetic melanin nanoparticles (SMNP) and a bioactive drug kartogenin (KGN) for theranostic purpose. We found that the SMNP‐KGN/Gel showed favorable mechanical property, thermal stability, and distinct magnetic resonance imaging (MRI) contrast enhancement. Meanwhile, the sustained release of KGN could recruit bone‐derived mesenchymal stem cells to proliferate and differentiate into chondrocytes, which promoted cartilage regeneration in vitro and in vivo. The hydrogel degradation and cartilage restoration were simultaneously monitored by multiparametric MRI for 12 weeks, and further confirmed by histological analysis. Together, these results validated the multifunctional hydrogel as a promising tissue engineering platform for noninvasive imaging‐guided precision therapy in cartilage regenerative medicine
Different Mechanisms of Coke Precursor Formation in Thermal Conversion and Deep Hydroprocessing of Vacuum Residue
Coke
formation during the refining of heavy oils has attracted extensive
attention as a result of the effects on the liquid yield, catalyst
deactivation, and operating period. Polycyclic aromatic hydrocarbons
(PAHs) generally have the strongest tendencies to form coke during
the refining processes, which are considered as coke precursors. In
this work, a vacuum residue was treated by thermal conversion and
deep hydroprocessing. The feedstock and products were characterized
by Fourier transform ion cyclotron resonance mass spectrometry. The
detailed distributions of aromatic hydrocarbons of the products behaved
with clear boundaries, which were described in limit lines. The slopes
of the limit lines differed greatly between the two kinds of products,
indicating different mechanisms for the growth of PAHs. Thermal conversion
and deep hydroprocessing of model compounds were also conducted. Thermal
conversion products of phenanthrene and pyrene proved that only condensation
reactions occurred at a temperature of 450 °C and the aromatic
rings were not ruptured. Deep hydroprocessing of pyrene revealed that
the aromatic ring structures were cracked and then the smaller aromatic
substrates combined together to form highly condensed aromatic rings.
As a conclusion, the different mechanisms of coke precursor formation
resulted in the different slopes of limit lines for thermal conversion
and deep hydroprocessing products