Fostering a Holistic Understanding of the Full Volatility Spectrum of Organic Compounds from Benzene Series Precursors through Mechanistic Modeling.

A comprehensive understanding of the full volatility spectrum of organic oxidation products from the benzene series precursors is important to quantify the air quality and climate effects of secondary organic aerosol (SOA) and new particle formation (NPF). However, current models fail to capture the full volatility spectrum due to the absence of important reaction pathways. Here, we develop a novel unified model framework, the integrated two-dimensional volatility basis set (I2D-VBS), to simulate the full volatility spectrum of products from benzene series precursors by simultaneously representing first-generational oxidation, multigenerational aging, autoxidation, dimerization, nitrate formation, etc. The model successfully reproduces the volatility and O/C distributions of oxygenated organic molecules (OOMs) as well as the concentrations and the O/C of SOA over wide-ranging experimental conditions. In typical urban environments, autoxidation and multigenerational oxidation are the two main pathways for the formation of OOMs and SOA with similar contributions, but autoxidation contributes more to low-volatility products. NOx can reduce about two-thirds of OOMs and SOA, and most of the extremely low-volatility products compared to clean conditions, by suppressing dimerization and autoxidation. The I2D-VBS facilitates a holistic understanding of full volatility product formation, which helps fill the large gap in the predictions of organic NPF, particle growth, and SOA formation.

Secondary Organic Aerosol Formation from the Photooxidation of Aromatic Ketone Intermediate Volatile Organic Compounds.

Oxygenated aromatics are substantial secondary organic aerosol (SOA) precursors, such as benzyl alcohol and phenolic compounds. Aromatic ketone intermediate volatile organic compounds (IVOCs), as a subclass of oxygenated aromatics, were found in anthropogenic source emissions and may contribute to SOA formation. However, the SOA yields and formation pathways of aromatic ketone IVOCs remain unknown. In this study, the photooxidations of aromatic ketone IVOCs in the absence and presence of NOx were studied in an oxidation flow reactor, and the particle- and gas-phase oxidation products were measured. The maximum SOA yields of benzophenone and 1,2-diphenylethanone are 0.24 and 0.33-0.35, respectively, relatively high among oxygenated aromatics. The SOA yields in the presence of NOx are 2-3 times higher than those in the absence of NOx in the late stage of oxidation. As the photooxidation proceeds, H/C of SOA slightly increases with O/C, and a greater amount of more-oxidized ring-retaining products exists in the particle phase in the presence of NOx. Based on gas-phase products and possible reaction pathways, functionalization of benzoic acid via the phenolic pathway is favored in the presence of NOx. Thus, our study highlights the significant SOA formation from aromatic ketone IVOCs, especially in the presence of NOx during long-time photooxidation.

In vitro evaluation of the toxicological effects of cooking oil fumes using a self-designed microfluidic chip.

Cooking oil fumes (COFs) are widely acknowledged as substantial contributors to indoor air pollution, having detrimental effects on human health. Despite the existence of commercialized in vitro aerosol exposure platforms, assessment risks of aerosol pollutants are primarily evaluated based on multiwell plate experiments by trapping and redissolving aerosols to conduct comprehensive in vitro immersion exposure manner. Therefore, an innovative real-time exposure system for COF aerosol was constructed, featuring a self-designed microfluidic chip as its focal component. The chip was used to assess toxicological effects of in vitro exposure to COF aerosol on cells cultured at the gas-liquid interface. Meanwhile, we used transcriptomics to analyze genes that exhibited differential expression in cells induced by COF aerosol. The findings indicated that the MAPK signaling pathway, known for its involvement in inflammatory response and oxidative stress, played a crucial role in the biological effects induced by COF aerosol. Biomarkers associated with inflammatory response and oxidative stress exhibited corresponding alterations. Furthermore, the concentration of COF aerosol exposure and post-exposure duration exert decisive effects on these biomarkers. Thus, the study suggests that COF can induce oxidative stress and inflammatory response in BEAS-2B cells, potentially exerting a discernible impact on human health.

Significant feature suppression and cross-feature fusion networks for fine-grained visual classification.

The technique of extracting different distinguishing features by locating different part regions to achieve fine-grained visual classification (FGVC) has made significant improvements. Utilizing attention mechanisms for feature extraction has become one of the mainstream methods in computer vision, but these methods have certain limitations. They typically focus on the most discriminative regions and directly combine the features of these parts, neglecting other less prominent yet still discriminative regions. Additionally, these methods may not fully explore the intrinsic connections between higher-order and lower-order features to optimize model classification performance. By considering the potential relationships between different higher-order feature representations in the object image, we can enable the integrated higher-order features to contribute more significantly to the model's classification decision-making capabilities. To this end, we propose a saliency feature suppression and cross-feature fusion network model (SFSCF-Net) to explore the interaction learning between different higher-order feature representations. These include (1) an object-level image generator (OIG): the intersection of the output feature maps of the last two convolutional blocks of the backbone network is used as an object mask and mapped to the original image for cropping to obtain an object-level image, which can effectively reduce the interference caused by complex backgrounds. (2) A saliency feature suppression module (SFSM): the most distinguishing part of the object image is obtained by a feature extractor, and the part is masked by a two-dimensional suppression method, which improves the accuracy of feature suppression. (3) A cross-feature fusion method (CFM) based on inter-layer interaction: the output feature maps of different network layers are interactively integrated to obtain high-dimensional features, and then the high-dimensional features are channel compressed to obtain the inter-layer interaction feature representation, which enriches the output feature semantic information. The proposed SFSCF-Net can be trained end-to-end and achieves state-of-the-art or competitive results on four FGVC benchmark datasets.

Analysis of the response to cigarette smoke exposure in cell coculture and monoculture based on bionic-lung microfluidic chips.

BACKGROUND: In vitro toxicity assessment studies with various experimental models and exposure modalities frequently generate diverse outcomes. In the prevalent experimental, aerosol pollutants are dissolved in culture medium through capture for exposure to two-dimensional planar cellular models in multiwell plates via immersion. However, this approach can generate restricted and inconclusive experimental data, significantly constraining the applicability of risk assessment outcomes. Herein, the in vitro cocultivation of lung epithelial and/or vascular endothelial cells was performed using self-designed bionic-lung microfluidic chip housing a gas-concentration gradient generator (GCGG) unit. Exposure experiments involving a concentration gradient of cigarette smoke (CS) aerosol were then conducted through an original assembled real-time aerosol exposure system. RESULTS: Transcriptomic analysis revealed a potential involvement of the cGMP-signaling pathway following online CS aerosol exposure on different cell culture models. Furthermore, distinct responses to different concentrations of CS aerosol exposure on different culture models were highlighted by detecting inflammation- and oxidative stress-related biomarkers (i.e., cell viability, reactive oxygen species, nitric oxide, IL-6, IL-8, TNF-α, GM-CSF, malondialdehyde, and superoxide dismutase). SIGNIFICANT: The results underscore the importance of improving chip biomimicry while addressing multi-throughput demands, given the substantial influence of the coculture model on cellular responses triggered by CS. Furthermore, the coculture model exhibited a mutually beneficial protective effect on cells at low CS concentrations within the GCGG unit, yet revealed a mutually amplified damaging effect at higher CS concentrations in contrast to the monoculture model.

Investigation of the in vitro toxic effects induced by real-time aerosol of electronic cigarette solvents using microfluidic chips.

The safety of propylene glycol (PG) and vegetable glycerin (VG) as solvents in electronic cigarette liquid has received increasing attention and discussion. However, the conclusions derived from toxicity assessments conducted through animal experiments and traditional in vitro methodologies have consistently been contentious. This study constructed an original real-time aerosol exposure system, centered around a self-designed microfluidic bionic-lung chip, to assess the biological effects following exposure to aerosols from different solvents (PG, PG/VG mixture alone and PG/VG mixture in combination with nicotine) on BEAS-2B cells. The study aimed to investigate the impact of aerosols from different solvents on gene expression profiles, intracellular biomarkers (i.e., reactive oxygen species content, nitric oxide content, and caspase-3/7 activity), and extracellular biomarkers (i.e., IL-6, IL-8, TNF-α, and malondialdehyde) of BEAS-2B cells on-chip. Transcriptome analyses suggest that ribosomal function could serve as a potential target for the impact of aerosols derived from various solvents on the biological responses of BEAS-2B cells on-chip. And the results showed that aerosols of PG/VG mixtures had significantly less effect on intracellular and extracellular biomarkers in BEAS-2B cells than aerosols of PG, whereas increasing nicotine levels might elevate these effects of aerosol from PG/VG mixture.

Differentiated emissions and secondary organic aerosol formation potential of organic vapor from industrial coatings in China.

Organic vapors emitted during solvent use are important precursors of secondary organic aerosols (SOAs). Industrial coatings are a major class of solvents that emit volatile and intermediate volatile organic compounds (VOCs and IVOCs, respectively). However, the emission factors and source profiles of VOCs and IVOCs from industrial coatings remain unclear. In this study, representative solvent- and water-based industrial paints were evaporated, sampled and tested using online and offline instruments. The VOC and IVOC emission factors for solvent-based paints are 129-254 and 25-80 g/kg, while for water-based paint are 13 and 32 g/kg, respectively. In solvent-based paints, the VOCs are mainly aromatics, while the IVOCs are composed of long-chain alkanes, alkenes, carbonyls and halocarbons. The VOCs and IVOCs in water-based paint are mostly oxygenates, such as ethanol, acetone, ethylene glycol, and Texanol. During the evaporation of solvent-based paints, the fraction of IVOCs increases along with those of alkenes and aldehydes, while the proportion of aromatics decreases. For water-based paint, the fraction of IVOCs slightly decreases with evaporation. The SOA formation potentials of solvent-based paints are 8.6-28.0 g/kg, much higher than that of water-based paint (0.65 g/kg); thus, substituting solvent-based paints with water-based paints may significantly decrease SOA formation.

The application of a self-designed microfluidic lung chip in the assessment of different inhalable aerosols.

Microfluidic-based assessment platforms have recently attracted considerable attention and have been widely used for evaluating in vitro toxic effects. In the present study, we developed an original real-time aerosol exposure system, which focused on a self-designed microfluidic chip, in order to evaluate the toxicological effects following exposure to inhalable aerosols. The three-layer structured microfluidic chip enables real-time aerosol exposure at the gas-liquid interface. The comprehensive detection of toxic effect biomarkers based on this assessment platform encompasses transcriptomics, in situ fluorescence detection, and the identification of extracellular secretagogues. Correspondingly, the effects of selected inhalable aerosols such as cigarette smoke (CS), heated tobacco product smoke (HS), and electronic cigarette smoke (ES) on gene expression profiles, cell viability, intracellular biomarkers (reactive oxygen species and nitric oxide), apoptosis (caspase-3/7 activity), and extracellular biomarkers (IL-8, IL-1ß, TNF-α, and malondialdehyde) in the BEAS-2B cells present on the chip were investigated. Following exposure to aerosols derived from CS, HS, and ES, the transcriptome analysis revealed differential expression in these cells. In addition, the overlapping DEGs from the different treatment groups were found to be primarily associated with stimuli and inflammatory responses. Correspondingly, each of the three categories of selected inhalable aerosols was confirmed to induce significant changes in biomarkers that were associated with toxic effects. These results suggest that the original real-time aerosol exposure system centered around a self-designed chip can be applied to the toxic effect evaluation of inhalable aerosol exposure.

Combining a lung microfluidic chip exposure model with transcriptomic analysis to evaluate the inflammation in BEAS-2B cells exposed to cigarette smoke.

BACKGROUND: Typically, in vitro studies on the exposure of complex gaseous substances are performed in multi-well plate experiments by trapping and redissolving them, which could introduce potential bias into the results due to the use of inadequate trapping methods. Therefore, a more effective method is to expose complex gaseous substances in gaseous form online, such as using microfluidic chips in experiments. To address these challenges, we introduce a methodology that integrates a self-designed bionic-lung chip with transcriptome analysis to assess the impact of cigarette smoke (CS) exposure on changes in BEAS-2B cells cultured on-chip. RESULTS: After the microfluidic chip underwent online gas exposure, total RNA was extracted via in situ cell lysis, and RNA-Seq transcriptome analysis was conducted. And the RNA-Seq findings revealed the significant involvement of the MAPK signaling pathway associated with the inflammatory response in the cellular effects induced by CS exposure. Moreover, the validation of inflammatory response-related biomarkers through in situ fluorescence corroborated the outcomes of the transcriptome analysis. Besides, the experiment involving the inhibition of inflammation by DEX on the microfluidic chip provided additional confirmation of the previous experimental findings. SIGNIFICANT: In this study, we present an analytical strategy that combines microfluidic-based CS in situ exposure method with RNA-Seq technology. This strategy offers an experimental scheme for in situ exposure to complex gases, transcriptome analysis, and in situ fluorescence detection. Through the integration of the comprehensiveness of transcriptome analysis with the chip's direct and intuitive in situ fluorescence detection with the stability and reliability of RT-PCR and Western blot experiments, we have successfully addressed the challenges associated with in vitro risk assessment for online exposure to complex gaseous substances.

Response of organic aerosol in Beijing to emission reductions during the XXIV Olympic Winter Games.

Organic aerosol (OA) serves as a crucial component of fine particulate matter. However, the response of OA to changes in anthropogenic emissions remains unclear due to its complexity. The XXIV Olympic Winter Games (OWG) provided real atmospheric experimental conditions on studying the response of OA to substantial emission reductions in winter. Here, we explored the sources and variations of OA based on the observation of aerosol mass spectrometer (AMS) combined with positive matrix factorization (PMF) analysis in urban Beijing during the 2022 Olympic Winter Games. The influences of meteorological conditions on OA concentrations were corrected by CO and verified by deweathered model. The CO-normalized primary OA (POA) concentrations from traffic, cooking, coal and biomass burning during the OWG decreased by 39.8 %, 23.2 % and 65.0 %, respectively. Measures controlling coal and biomass burning were most effective in reducing POA during the OWG. For the CO-normalized concentration of secondary OA (SOA), aqueous-phase related oxygenated OA decreased by 51.8 % due to the lower relative humidity and emission reduction in precursors, while the less oxidized­oxygenated OA even slightly increased as the enhanced atmospheric oxidation processes may partially offset the efficacy of emission control. Therefore, more targeted reduction of organic precursors shall be enhanced to lower atmospheric oxidation capacity and mitigate SOA pollution.