We conducted homogeneous nucleation experiments for dilute binary H2O-CO2 mixtures in Ar-N2 carrier gas with different CO2/H2O ratios at temperatures of 57 and 75 K and total pressures of ∼40 and 70 Pa, respectively. Direct experimental information on the number and type of molecules in the clusters and on the cluster number concentration is obtained by mass spectrometric detection of nucleating clusters that form in the uniform region of Laval expansions. Only homo-molecular water clusters are observed in the mass spectra. However, as the CO2/H2O ratio increases, a significant increase in the nucleation rate is observed. A simple kinetic model suggests that this acceleration of nucleation is due to the formation of short-lived, transient hetero-molecular H2O-CO2 dimers. Comparison with homogeneous binary nucleation of toluene-CO2 and unary nucleation of H2O shows that nucleation becomes more efficient in systems with stronger intermolecular interactions and a larger number of degrees of freedom. Such studies at the molecular level will improve our understanding of homogeneous nucleation mechanisms in atmospheric and industrial processes.
To assess the efficacy and safety of application of a toothpaste containing lysozyme to remove extrinsic stains on the tooth surface in an 8-week trial.70 adult participants with extrinsic staining of the tooth surface were recruited to this randomized, parallel-controlled, double-blind clinical trial. Participants were allocated randomly to the test group or the control group and the study procedure and correct usage of the toothpaste were explained to them. Staining, measured by the Lobene stain index, and any side effects, were recorded over the course of the 8 weeks. All data were analyzed using SAS software version 8.0.69 participants completed the study. The value of the Lobene stain index was significantly reduced (P< 0.05) in the treatment group compared with the control group after both 4 and 8 weeks. No obvious side effects were observed.The results of this clinical study showed that the toothpaste containing lysozyme was effective in removing extrinsic staining on the tooth surface.
Abstract Organosulfates (OSs) are important components of secondary organic aerosols (SOA) in the atmosphere. Despite the frequent observation of OSs in field and laboratory studies, the sources and detailed formation pathways of these species, particularly in polluted regions, are still not well understood. In this study, a total of 156 ambient PM 2.5 filter samples were collected in a Chinese megacity (Shanghai) over four seasons in both 2015–2016 and 2018–2019. More than 270 OS formulas were detected in ambient aerosols using high‐resolution liquid chromatography‐mass spectrometry. Interestingly, a series of alkyl OSs, C n H 2n+1 O 4 S − (C 5 –C 11 ), were observed, which are most likely to be produced from the heterogeneous reactions of organic peroxides with sulfur dioxide or sulfate. The observation of these compounds provides the first field evidence for atmospheric OS formation involving organic peroxides. By employing a positive matrix factorization model, the possible precursors of OSs were classified into six groups, that is, isoprene‐derived, monoterpene‐derived, aromatic, short‐chain aliphatic, long‐chain aliphatic, and anthropogenic C 2 /C 3 OSs. Biogenic (isoprene and monoterpenes) and anthropogenic sources (the remaining factors) contributed to 57.2% and 42.8% of OS formation in 2015–2016, respectively, and their contributions just slightly changed in 2018–2019. In addition, the OS sources exhibited strong seasonality. Isoprene‐derived OSs contributed to the largest fraction of total OSs in summer, while anthropogenic sources dominated OS formation in other seasons. Our findings provide valuable insight into OS sources and formation mechanisms in the atmosphere and highlight the importance of both biogenic and anthropogenic emissions for the formation of OSs in a typical Chinese megacity.
In 2020, Fanconi anemia (FA) was classified as a syndrome with insufficient epidemiological evidence in the oral potentially malignant disorder (OPMD) group by the WHO Collaborating Centre. The paucity of case reports on FA-associated OPMD limits evidence-based management, and such cases have not been analyzed collectively in detail. Hence, the objective of this short communication is to summarize the evidence on the onset and progression of OPMD in FA patients, so as to better understand the natural history of oral cancer development in patients affected by FA. A total of 11 eligible papers containing 1332 FA patients are involved in onset and progression of OPMD in FA patients. Of these, 186 (14.0%) were diagnosed with OPMD. With available data from 4 follow-up studies, 30 (41.1%) of 73 FA patients compatible with OPMD further developed into OSCC at young age (10-30 years old). The evidence on FA with malignant potential comprise clinical epidemiology, oral cytology abnormalities, DNA aneuploidy, loss of autofluorescence, loss of heterozygosity, high-risk human papillomavirus infection, DNA mutations in saliva and plasma samples. Collectively, these can consummate the evidence on FA as a syndrome that may potentiate cancer development in oral cavity mentioned by the WHO. Importantly, it highlights close surveillance is instrumental for FA patients with OPMD to early detect oral cancer.
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