Observation of anti-damping spin-orbit torques generated by in-plane and out-of-plane spin polarizations in MnPd3.

Large spin-orbit torques (SOTs) generated by topological materials and heavy metals interfaced with ferromagnets are promising for next-generation magnetic memory and logic devices. SOTs generated from y spin originating from spin Hall and Edelstein effects can realize field-free magnetization switching only when the magnetization and spin are collinear. Here we circumvent the above limitation by utilizing unconventional spins generated in a MnPd3 thin film grown on an oxidized silicon substrate. We observe conventional SOT due to y spin, and out-of-plane and in-plane anti-damping-like torques originated from z spin and x spin, respectively, in MnPd3/CoFeB heterostructures. Notably, we have demonstrated complete field-free switching of perpendicular cobalt via out-of-plane anti-damping-like SOT. Density functional theory calculations show that the observed unconventional torques are due to the low symmetry of the (114)-oriented MnPd3 films. Altogether our results provide a path toward realization of a practical spin channel in ultrafast magnetic memory and logic devices.

Seasonal meropenem resistance in Acinetobacter baumannii and influence of temperature-driven adaptation.

BACKGROUND: Recognition of seasonal trends in bacterial infection and drug resistance rates may enhance diagnosis, direct therapeutic strategies, and inform preventive measures. Limited data exist on the seasonal variability of Acinetobacter baumannii. We investigated the seasonality of A. baumannii, the correlation between temperature and meropenem resistance, and the impact of temperature on this bacterium. RESULTS: Meropenem resistance rates increased with lower temperatures, peaking in winter/colder months. Nonresistant strain detection exhibited temperature-dependent seasonality, rising in summer/warmer months and declining in winter/colder months. In contrast, resistant strains showed no seasonality. Variations in meropenem-resistant and nonresistant bacterial resilience to temperature changes were observed. Nonresistant strains displayed growth advantages at temperatures ≥ 25 °C, whereas meropenem-resistant A. baumannii with ß-lactamase OXA-23 exhibited greater resistance to low-temperature (4 °C) stress. Furthermore, at 4 °C, A. baumannii upregulated carbapenem resistance-related genes (adeJ, oxa-51, and oxa-23) and increased meropenem stress tolerance. CONCLUSIONS: Meropenem resistance rates in A. baumannii display seasonality and are negatively correlated with local temperature, with rates peaking in winter, possibly linked to the differential adaptation of resistant and nonresistant isolates to temperature fluctuations. Furthermore, due to significant resistance rate variations between quarters, compiling monthly or quarterly reports might enhance comprehension of antibiotic resistance trends. Consequently, this could assist in formulating strategies to control and prevent resistance within healthcare facilities.

Rare-Earth Metal Complexes Bearing Electrophilic Carbon and Strongly Polarized Metallacyclopropane Moiety: Synthesis and Diverse Reactivity toward Small Molecules.

Metallacyclopropanes are highly strained and very reactive organometallics; the rare-earth metal complexes bearing both highly reactive electrophilic carbon and strongly polarized metallacyclopropanes are extremely rare. This type of rare-earth metal complexes (κ2-L)RE(η2-C2B10H10)·(THF)3 [L = 1-(2-N-C5H10NCH2CH2)-3-(2,6-iPr2C6H3N═CH)-C8H4N, RE = Lu(1a), Yb(1b), Er(1c), Y(1d), Dy(1e)] bearing the indol-2-yl electrophilic carbon and carboryne-based strongly polarized metallacyclopropanes have been synthesized. Structures of complexes 1 are further confirmed by single-crystal X-ray diffraction and DFT theoretical calculations. It is found that complexes 1 have remarkable reactivity toward different polar unsaturated small molecules, elemental sulfur, and selenium to provide different products (2-15) through the selective reactions of the RE-Ccage, and RE-C2-ind bonds with the given small molecules, respectively. The reactivities of these complexes are different from those of the reported rare-earth metallacyclopropenes and d-block metal-carborynes.

Oxidation of Polycyclic Aromatic Hydrocarbons (PAHs) Triggered by a Photochemical Synergistic Effect between High- and Low-Molecular-Weight PAHs.

Photooxidation of polycyclic aromatic hydrocarbons (PAHs), which are widely observed in atmospheric particulate matter (PM), largely determines their atmospheric fate. In the environment, PAHs are highly complex in chemical composition, and a great variety of PAHs tend to co-occur. Despite extensive investigation on the photochemical behavior of individual PAH molecules, the photochemical interaction among these coexisting PAHs is still not well understood. Here, we show that during photooxidation, there is a strong photochemical synergistic effect among PAHs extracted from soot particles. We find that neither small PAHs with low molecular weights of 200-350 Da and 4-8 aromatic rings (named PAHsmall) nor large PAHs with high molecular weights of 350-600 Da and 8-14 aromatic rings (named PAHlarge) undergo photooxidation under red-light irradiation (λ = 648 nm), even though PAHlarge can absorb light with this wavelength. Interestingly, when PAHlarge is mixed with PAHsmall, substantial photooxidation is observed for both PAHlarge and PAHsmall. Comparisons of in situ infrared (IR), high-resolution mass spectrometry, and electron paramagnetic resonance analysis indicate that the presence of PAHsmall inhibits the light quenching effect arising from the π-π stacking of PAHlarge. This leads to the formation of singlet oxygen (1O2), which initiates the photooxidation. Our findings reveal a new mechanism for the photooxidation of PAHs and suggest that complex atmospheric PAHs exhibit distinct photoreactivity from simple systems.

Single Droplet Tweezer Revealing the Reaction Mechanism of Mn(II)-Catalyzed SO2 Oxidation.

Sulfate aerosol is one of the major components of secondary fine particulate matter in urban haze that has crucial impacts on the social economy and public health. Among the atmospheric sulfate sources, Mn(II)-catalyzed SO2 oxidation on aerosol surfaces has been regarded as a dominating one. In this work, we measured the reaction kinetics of Mn(II)-catalyzed SO2 oxidation in single droplets using an aerosol optical tweezer. We show that the SO2 oxidation occurs at the Mn(II)-active sites on the aerosol surface, per a piecewise kinetic formulation, one that is characterized by a threshold surface Mn(II) concentration and gaseous SO2 concentration. When the surface Mn(II) concentration is lower than the threshold value, the reaction rate is first order with respect to both Mn(II) and SO2, agreeing with our traditional knowledge. But when surface Mn(II) concentration is above the threshold, the reaction rate becomes independent of Mn(II) concentration, and the reaction order with respect to SO2 becomes greater than unity. The measured reaction rate can serve as a tool to estimate sulfate formation based on field observation, and our established parametrization corrects these calculations. This framework for reaction kinetics and parametrization holds promising potential for generalization to various heterogeneous reaction pathways.

Global, regional, and national total burden related to hepatitis B in children and adolescents from 1990 to 2021.

BACKGROUND: Hepatitis B remains a significant global health concern with widespread communicability. Nevertheless, data on its burden and trends in children and adolescents were limited. We aim to evaluate the global, regional, and national trends of total burden related to hepatitis B in children and adolescents aged 0-19 years from 1990 to 2021. METHODS: The age-standardized incidence, prevalence, mortality, and disability-adjusted life years (DALYs) were calculated by the Global Burden of Disease (GBD) study from 1990 to 2021. These indicators were stratified by sex, age, socio-demographic index (SDI), and disease stage. We calculated the correlation between them and SDI. The temporal trends were examined using the annual average percentage change (AAPC) and joinpoint regression. RESULTS: The global age-standardized incidence of hepatitis B in children and adolescents decreased from 1385.20 per 100,000 population in 1990 to 418.68 per 100,000 population in 2021, with an AAPC of -3.76%. Similarly, age-standardized DALYs decreased from 70.78 per 100,000 population to 36.31 per 100,000 population, with an AAPC of -2.13%. The age-standardized prevalence (AAPC - 3.53%) and mortality (AAPC - 2.09%) of hepatitis B also decreased significantly. From 1990 to 2021, the age-standardized incidence and prevalence among males exhibited a higher trend compared to females, although both declined over time. These two indicators also decreased across all age subgroups, with consistently higher rates observed in the 15-19 age group compared to other age groups. The burden of hepatitis B demonstrated a notable reduction in countries with high-middle SDI, while it was highest in countries with low SDI. In 2021, Central sub-Saharan Africa and West sub-Saharan Africa reported the highest age-standardized incidence. For age-standardized DALYs, South Asia was the only region to experience an increase (AAPC 1.09%), while East Asia showed the largest decline (AAPC - 7.58%). Alcohol and drug use remained important risk factors for DALYs among people aged 15-19 years. Furthermore, the impact of drug use on disease burden was increasing, particularly in high-SDI countries. CONCLUSIONS: The global burden and trends of hepatitis B decreased significantly in children and adolescents, exhibiting regional and national variations. Management of alcohol and drug use remains a major challenge for people aged 15-19 years.

The predicting role of serum tumor-specific growth factor for prognosis of esophageal squamous cell carcinoma.

OBJECTIVE: Tumor-specific growth factor (TSGF) is an immune-related factor that offers good performance in the clinical management of human cancers. However, the role of serum TSGF in esophageal squamous cell carcinoma (ESCC) has not been fully clarified. METHODS: A total of 562 ESCC cases were collected in our study, with available information on preoperative serum levels of TSGF at diagnosis. Preoperative serum TSGF was detected using the rate method. We retrospectively analyzed its correlation with clinicopathological features of ESCC and survival. RESULTS: The cut-off value of serum TSGF was determined to be 60.5 U/mL by receiver operating characteristic (ROC) analysis. Serum TSGF was associated with gender (P < 0.001), tumor location (P = 0.022), tobacco use (P < 0.001), alcohol consumption (P < 0.001), lymph node involvement (P = 0.007), and TNM staging (P = 0.004). The survival analysis revealed that ESCC patients with high levels of serum TSGF had poorer prognosis than those with high TSGF (P = 0.006), especially for male ESCC cases (P = 0.001), under 60 year (P = 0.036), male middle location (P = 0.023), tobacco consumption (P = 0.004), G1 + G2 (P = 0.031), advanced T staging (P = 0.033), lymph node involvement (P = 0.003), TNM staging (P = 0.003). Univariate Cox regression analysis indicated that exposure to smoking and drinking, tumor grade, T staging, lymph node metastasis, TNM staging, and serum TSGF level were the prognosis-related factors of ESCC. Multivariate regression analysis revealed that smoking history, higher serum TSGF levels, and advanced T stage enhanced the risk of ESCC-related death. CONCLUSION: In brief, serum TSGF levels had in relation to malignant features of ESCC. It was positively correlated with survival but was identified as an independent risk factor for ESCC.

Remarkable nucleation and growth of ultrafine particles from vehicular exhaust.

High levels of ultrafine particles (UFPs; diameter of less than 50 nm) are frequently produced from new particle formation under urban conditions, with profound implications on human health, weather, and climate. However, the fundamental mechanisms of new particle formation remain elusive, and few experimental studies have realistically replicated the relevant atmospheric conditions. Previous experimental studies simulated oxidation of one compound or a mixture of a few compounds, and extrapolation of the laboratory results to chemically complex air was uncertain. Here, we show striking formation of UFPs in urban air from combining ambient and chamber measurements. By capturing the ambient conditions (i.e., temperature, relative humidity, sunlight, and the types and abundances of chemical species), we elucidate the roles of existing particles, photochemistry, and synergy of multipollutants in new particle formation. Aerosol nucleation in urban air is limited by existing particles but negligibly by nitrogen oxides. Photooxidation of vehicular exhaust yields abundant precursors, and organics, rather than sulfuric acid or base species, dominate formation of UFPs under urban conditions. Recognition of this source of UFPs is essential to assessing their impacts and developing mitigation policies. Our results imply that reduction of primary particles or removal of existing particles without simultaneously limiting organics from automobile emissions is ineffective and can even exacerbate this problem.

Clinical features and prognostic factors of breast cancer in young women: a retrospective single-center study.

PURPOSE: This research aims to characterize the differences in clinical features and prognostic factors between younger and older breast cancer (BC) patients in China. METHODS: All patients who were recently diagnosed with BC between January 1, 2015 and December 31, 2016 at Shanxi Province Cancer Hospital were recruited. We collected the epidemiological and clinical data as well as the follow-up information. RESULTS: Out of the 1968 BC patients who met the criteria for analysis, 227 (11.53%) were under 40 years of age with a median age of 34 years at diagnosis. All patients were classified into the age < 40, age 40-59, and age ≥ 60 groups. There were significant differences in the histology, tumor size, T stage, grade, and human epidermal growth factor receptor-2 (HER-2) levels among the three groups (all P < 0.05). The 5-year overall survival (OS) rates were 86.34%, 89.58%, and 84.84% for the age < 40, age 40-59, and age ≥ 60 groups, respectively. The TNM stage was the only predictor of clinical outcome in all BC patients. The prognostic value of intrinsic subtypes for OS was different among the three groups. CONCLUSION: Our study helped identify an age-related prognostic indicator of adverse events in BC patients and showed that young women with BC exhibited more aggressive clinical and pathological features. Our findings may facilitate clinical management and therapeutic interventions in young BC patients, especially in young women with a history of exposure to risk factors and age < 40 years.

Recent Progress in Atmospheric Chemistry Research in China: Establishing a Theoretical Framework for the "Air Pollution Complex".

Atmospheric chemistry research has been growing rapidly in China in the last 25 years since the concept of the "air pollution complex" was first proposed by Professor Xiaoyan TANG in 1997. For papers published in 2021 on air pollution (only papers included in the Web of Science Core Collection database were considered), more than 24 000 papers were authored or co-authored by scientists working in China. In this paper, we review a limited number of representative and significant studies on atmospheric chemistry in China in the last few years, including studies on (1) sources and emission inventories, (2) atmospheric chemical processes, (3) interactions of air pollution with meteorology, weather and climate, (4) interactions between the biosphere and atmosphere, and (5) data assimilation. The intention was not to provide a complete review of all progress made in the last few years, but rather to serve as a starting point for learning more about atmospheric chemistry research in China. The advances reviewed in this paper have enabled a theoretical framework for the air pollution complex to be established, provided robust scientific support to highly successful air pollution control policies in China, and created great opportunities in education, training, and career development for many graduate students and young scientists. This paper further highlights that developing and low-income countries that are heavily affected by air pollution can benefit from these research advances, whilst at the same time acknowledging that many challenges and opportunities still remain in atmospheric chemistry research in China, to hopefully be addressed over the next few decades.

Measurement of atmospheric nanoparticles: Bridging the gap between gas-phase molecules and larger particles.

Atmospheric nanoparticles are crucial components contributing to fine particulate matter (PM2.5), and therefore have significant effects on visibility, climate, and human health. Due to the unique role of atmospheric nanoparticles during the evolution process from gas-phase molecules to larger particles, a number of sophisticated experimental techniques have been developed and employed for online monitoring and characterization of the physical and chemical properties of atmospheric nanoparticles, helping us to better understand the formation and growth of new particles. In this paper, we firstly review these state-of-the-art techniques for investigating the formation and growth of atmospheric nanoparticles (e.g., the gas-phase precursor species, molecular clusters, physicochemical properties, and chemical composition). Secondly, we present findings from recent field studies on the formation and growth of atmospheric nanoparticles, utilizing several advanced techniques. Furthermore, perspectives are proposed for technique development and improvements in measuring atmospheric nanoparticles.

Atmospheric environment monitoring technology and equipment in China: A review and outlook.

Accurate monitoring of the atmospheric environment and its evolution are important for understanding the sources, chemical mechanisms, and transport processes of air pollution and carbon emissions in China, and for regulatory and control purposes. This study gives an overview of atmospheric environment monitoring technology and equipment in China and summarizes the major achievements obtained in recent years. China has made great progress in the development of atmospheric environment monitoring technology and equipment with decades of effort. The manufacturing level of atmospheric environment monitoring equipment and the quality of products have steadily improved, and a technical & production system that can meet the requirements of routine monitoring activities has been initiated. It is expected that domestic atmospheric environment monitoring technology and equipment will be able to meet future demands for routine monitoring activities in China and provide scientific assistance for addressing air pollution problems.

Toxicological Effects of Secondary Air Pollutants.

Secondary air pollutants, originating from gaseous pollutants and primary particulate matter emitted by natural sources and human activities, undergo complex atmospheric chemical reactions and multiphase processes. Secondary gaseous pollutants represented by ozone and secondary particulate matter, including sulfates, nitrates, ammonium salts, and secondary organic aerosols, are formed in the atmosphere, affecting air quality and human health. This paper summarizes the formation pathways and mechanisms of important atmospheric secondary pollutants. Meanwhile, different secondary pollutants' toxicological effects and corresponding health risks are evaluated. Studies have shown that secondary pollutants are generally more toxic than primary ones. However, due to their diverse source and complex generation mechanism, the study of the toxicological effects of secondary pollutants is still in its early stages. Therefore, this paper first introduces the formation mechanism of secondary gaseous pollutants and focuses mainly on ozone's toxicological effects. In terms of particulate matter, secondary inorganic and organic particulate matters are summarized separately, then the contribution and toxicological effects of secondary components formed from primary carbonaceous aerosols are discussed. Finally, secondary pollutants generated in the indoor environment are briefly introduced. Overall, a comprehensive review of secondary air pollutants may shed light on the future toxicological and health effects research of secondary air pollutants.

Single-Cell VEGF Analysis by Fluorescence Imaging-Microfluidic Droplet Platform: An Immunosandwich Strategy on the Cell Surface.

Despite recent advances in single-cell analysis techniques, the ability of single-cell analysis platforms to track specific cells that secreted cytokines remains limited. Here, we report a microfluidic droplet-based fluorescence imaging platform that can analyze single cell-secreted vascular endothelial growth factor (VEGF), an important regulator of physiological and pathological angiogenesis, to explore cellular physiological clues at the single-cell level. Two kinds of silica nanoparticle (NP)-based immunoprobes were developed, and they were bioconjugated to the membrane proteins of the probed cell surface via the bridging of secreted VEGF. Thus, an immunosandwich assay was built above the probed cell via fluorescence imaging analysis of each cell in isolated droplets. This analytical platform was used to compare the single-cell VEGF secretion ability of three cell lines (MCF-7, HeLa, and H8), which experimentally demonstrates the cellular heterogeneity of cells in secreting cytokines. The uniqueness of this method is that the single-cell assay is carried out above the cell of interest, and no additional carriers (beads or reporter cells) for capturing analytes are needed, which dramatically improves the availability of microdroplets. This single-cell analytical platform can be applied for determining other secreted cytokines at the single-cell level by changing other immune pairs, which will be an available tool for exploring single-cell metabonomics.

Microfluidic Droplet-SERS Platform for Single-Cell Cytokine Analysis via a Cell Surface Bioconjugation Strategy.

A microfluidic-based surface-enhanced Raman scattering (SERS) platform for analyzing cytokines secreted by single cells is reported based on the elaborate bioconjugation of the immuno-sandwich complex on the probed cell surface. This platform integrates the dual functions of microfluidic droplet separation of single cells and SERS measurement. Two immune nanoprobes (capture probe and SERS probe) are introduced into a microfluidic droplet along with a single cell. They were anchored to the cell membrane protein surface by capturing secreted cytokines to form an immune sandwich structure, realizing the enrichment effect of cytokines above the cell membrane surface and the amplification effect of SERS detection probes. This single-cell analytical platform was applied to track specific cell-secreted vascular endothelial growth factor (VEGF) of different cell lines (MCF-7, SGC, and T24), and highly sensitive detection of VEGF was achieved. Chemometric methods (principal component analysis and t-distributed stochastic neighbor embedding) were adopted for the SERS data analysis, and the support vector machine (SVM) discriminant model was established to test the data. These chemometric methods successfully identify significant differences in the secreting ability of cytokines among three kinds of cancer cell lines, revealing cell heterogeneity. In addition, the behavior of single cells secreting VEGF was monitored time-dependently and was shown to increase with time. This work demonstrates the importance of tracking specific cells secreting cytokines based on the cell surface bioconjugation strategy. Our developed platform provides guidelines for using the single-cell exocytosis factors as biomarkers to assess the early diagnosis of cancer and provide physiological cues for learning single-cell secretions.

Silencing of lncRNA SNHG17 inhibits the tumorigenesis of epithelial ovarian cancer through regulation of miR-485-5p/AKT1 axis.

BACKGROUND: Epithelial ovarian cancer (EOC) stands up for about 90% of ovarian cancer cases, which is the frequent cause of death among women. LncRNAs are involved in progression of EOC. Meanwhile, lncRNA SNHG17 was upregulated in EOC, while the detailed function of SNHG17 in EOC remains unclear. METHODS: Protein and mRNA levels were assessed by western blot and RT-qPCR, respectively. The function of SNHG17 in EOC cells was tested by CCK-8, Ki-67 staining, flow cytometry and transwell assay. Dual luciferase was applied for assessing the relation among SNHG17, miR-485-5p and AKT1. Furthermore, in vivo experiments were applied to test the impact of SNHG17 in EOC. RESULTS: SNHG17 knockdown reduced the proliferation and promoted the apoptosis of EOC cells. Consistently, si-SNHG17 obviously reduced the invasion and epithelial-to-mesenchymal transition (EMT) process of EOC cells. MiR-485-5p was proved to be the target miRNA of SNHG17, and SNHG17 negatively regulated the level of miR-485-5p. MiR-485-5p inhibitor significantly abolished the anti-tumor impact of si-SNHG17 on EOC. AKT1 was identified to be targeted by miR-485-5p, and miR-485-5p negatively modulated AKT1 and p-mTOR levels. Moreover, miR-485-5p mimics reduced the proliferation, migration and promoted the apoptosis of EOC cells via targeting AKT1. Furthermore, si-SNHG17 markedly suppressed EOC growth in vivo. CONCLUSION: SNHG17 silencing inhibits the development of EOC via regulation of miR-485-5p/AKT1 axis. Thus, our study might supply a novel strategy against EOC.

Comparison of the pharmacokinetics of Crocin-I in normoxic and hypoxic rats.

An ultra-performance liquid chromatography with quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS) method for the simultaneous determination of Crocin-I and its primary metabolites Crocetin was established, and a comparison of metabolic characteristics in vivo is made to Crocin-I and Crocetin in normoxic and hypoxic rats after intragastric administration. The acute hypoxic rat model was established by simulating high altitude environment in a hypobaric hypoxia animal experimental chamber. After intragastric administration of 400 mg•kg-1 Crocin-I. UPLC-Q-TOF-MS method was used to detect the plasma concentrations of Crocin-I and Crocetin in plasma at different times. Compared with normoxic rats, the area under the curve (AUC), mean residence time (MRT), time to peak (Tmax), half-life (T1/2) and plasma concentration (Cmax) of plasma Crocin-I in hypoxic rats were significantly increased (P < 0.01). The apparent distribution (Vz/F) and clearance (CLz/F) of plasma Crocin-I in hypoxic rats were significantly decreased (P < 0.01). Under hypoxic conditions, the pharmacokinetic parameters of Crocin-I and its metabolite Crocetin change significantly. The results provide a theoretical basis for the feasibility of Crocin-I for anti-hypoxia treatment in terms of pharmacokinetics and provide an essential experimental basis for optimizing the drug dosing regimen.

Rapid Sulfate Formation via Uncatalyzed Autoxidation of Sulfur Dioxide in Aerosol Microdroplets.

Severe winter haze events in Beijing and North China Plain are characterized by rapid production of sulfate aerosols with unresolved mechanisms. Oxidation of SO2 by O2 in the absence of metal catalysts (uncatalyzed autoxidation) represents the most ubiquitous SO2 conversion pathway in the atmosphere. However, this reaction has long been regarded as too slow to be atmospherically meaningful. This traditional view was based on the kinetic studies conducted in bulk dilute solutions that mimic cloudwater but deviate from urban aerosols. Here, we directly measure the sulfate formation rate via uncatalyzed SO2 autoxidation in single (NH4)2SO4 microdroplets, by using an aerosol optical tweezer coupled with a cavity-enhanced Raman spectroscopy technique. We find that the aqueous reaction of uncatalyzed SO2 autoxidation is accelerated by two orders of magnitude at the high ionic strength (∼36 molal) conditions in the supersaturated aerosol water. Furthermore, at acidic conditions (pH 3.5-4.5), uncatalyzed autoxidation predominately occurs on droplet surface, with a reaction rate unconstrained by SO2 solubility. With these rate enhancements, we estimate that the uncatalyzed SO2 autoxidation in aerosols can produce sulfate at a rate up to 0.20 µg m-3 hr-1, under the winter air pollution condition in Beijing.

Sulfate Formation Apportionment during Winter Haze Events in North China.

There is a large gap between the simulated and observed sulfate concentrations during winter haze events in North China. Although multiphase sulfate formation mechanisms have been proposed, they have not been evaluated using chemical transport models. In this study, the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) was used to apportion sulfate formation. It was found that Mn-catalyzed oxidation on aerosol surfaces was the dominant sulfate formation pathway, accounting for 92.3 ± 3.5% of the sulfate formation during haze events. Gas-phase oxidation contributed 3.1 ± 0.5% to the sulfate formation due to the low OH levels. The H2O2 oxidation in aerosol water accounted for 4.2 ± 3.6% of the sulfate formation, caused by the rapid consumption of H2O2. The contributions of O3, NO2 oxidation, and transition metal ion-catalyzed reactions in aerosol water could be negligible owing to the low aerosol water content, low pH, and high ionic strength. The contributions from in-cloud reactions were negligible due to the barrier provided by stable stratification during winter haze events.

Reactions of C12-C14 n-Alkylcyclohexanes with Cl Atoms: Kinetics and Secondary Organic Aerosol Formation.

Long-chain alkanes are a type of intermediate volatility organic compound (IVOC) in the atmosphere and a potential source of secondary organic aerosols (SOAs). C12-C14 n-alkylcyclohexanes are important compositions of IVOCs, with considerable concentrations and emission rates. The reaction rate constants and SOA formation of the reactions of C12-C14 n-alkylcyclohexanes with Cl atoms were investigated in the present study. The reaction rate constants of the long-chain alkanes obtained via the relative-rate method at 298 ± 0.2 K (in units of ×10-10 cm3 molecule-1 s-1) were as follows: khexylcyclohexane = 5.11 ± 0.28, kheptylcyclohexane = 5.56 ± 0.30, and koctylcyclohexane = 5.74 ± 0.31. The gas-phase products of the reactions were identified as mainly small molecules of aldehydes, ketones, and acids. The particle-phase products were mostly monomers and oligomers, but there were still trimers even under high-NOx conditions. Moreover, under high-NOx conditions (urban atmosphere), the SOA yields of hexylcyclohexane are higher than that under low-NOx conditions (remote atmosphere), indicating that more attention should be given to the SOA formation of Cl-initiated n-alkylcyclohexane oxidations in polluted regions. This research can further clarify the oxidation processes and SOA formation of n-alkylcyclohexanes in the atmosphere.