A Study on Online Health Community Users' Information Demands Based on the BERT-LDA Model.

As the economy and society develop and the standard of living improves, people's health awareness increases and the demand for health information grows. This study introduces an advanced BERT-LDA model to conduct topic-sentiment analysis within online health communities. It examines nine primary categories of user information requirements: causes, symptoms and manifestations, examination and diagnosis, treatment, self-management and regulation, impact, prevention, social life, and knowledge acquisition. By analyzing the distribution of positive and negative sentiments across each topic, the correlation between various health information demands and emotional expressions is investigated. The model established in this paper integrates BERT's semantic comprehension with LDA's topic modeling capabilities, enhancing the accuracy of topic identification and sentiment analysis while providing a more comprehensive evaluation of user information demands. This research furthers our understanding of users' emotional reactions and presents valuable insights for delivering personalized health information in online communities.

Bar adsorptive microextraction device coated with polyimide microsphere assembled by nanosheets combined with thermal desorption-gas chromatography for trace analysis of nitroaromatic explosives in environmental waters.

Polyimide (PI) microspheres assembled by nanosheets were used for bar adsorptive microextraction (BAµE) for the first time. The PI microsphere possessed self-organized hierarchical nanostructure, large specific surface area (170 m2/g) and good thermostability (up to 400 °C). The BAµE device was prepared by adhering the PI microspheres on a quartz bar with Kapton double sided tape. Trace nitroaromatic explosives in environmental waters were extracted by the BAµE device, desorbed by thermal desorption (TD), and analyzed by gas chromatography-mass spectrometry (GC-MS). The reproducibility of five BAµE devices prepared in parallel was less than 13.0% (expressed as relative standard deviation, RSD). The BAµE device could stand up to 30 extraction/desorption cycles without decrease of extraction efficiency. The results of method validation showed that the BAµE-TD/GC-MS method possessed wide linearity (0.05-50 µg/L or 0.05-20 µg/L), high correlation coefficients (> 0.9987), good precision (RSDs < 11.8%), low detection limits (0.005-0.013 µg/L) and high enrichment factors (528-1410). Relative recoveries were in the range of 72.2-122.6% with RSDs between 0.1% and 10.5% for real water samples. These results proved that the proposed method was a good choice for determination of organic pollutants in water samples.

Porous polyimide particle-coated adsorptive microextraction bar combined with thermal desorption-gas chromatography for rapid determination of parabens in condiments.

Bar adsorptive microextraction using polyimide (PI) particles as the extraction phase followed by thermal desorption and gas chromatography-mass spectrometry (BAµE/TD-GC-MS) was developed to detect parabens in condiments, such as soy sauce, vinegar, and cooking wine. The PI particles were prepared by pneumatic spray combined with the immersion-precipitation phase transformation method. The prepared particles have highly porous surfaces, on which the 10-60 nm open nanopores are closely packed. Particles between 250-500 µm were then sieved out and used as extraction phase for BAµE. In contrast to the smooth and dense surface of the conventional PI phase transformation bar, the macroscopic rough surface of the PI particle bar and its microscopic porous particle surfaces provided larger extraction interfaces and more surface adsorption sites, both of which enhanced the extraction mass flux. With an extraction time of 2 min, the absolute recoveries of parabens by the PI particle bar were 1.9˜2.7 times those obtained by the conventional PI phase transformation bar. The intrabatch and interbatch precisions of the PI particle bars were less than 4.6% and 7.5%, respectively, and the PI particle bar exhibited a long lifetime of more than 50 extraction/desorption cycles. To realize rapid determination of parabens, the extraction time was fixed at 2 min. The analytical performance for standard water samples showed wide linearity (0.14-50 µg/L) with good correlation coefficients (r > 0.9980), good precision (RSD < 5.6%), appropriate detection limits (0.005-0.008 µg/L), and high enrichment factors (305-626). For the analysis of parabens in diluted condiments, the relative recoveries were between 86.1% and 109.0% with RSDs ranging from 0.1%-8.7%.

Inhibition of water adsorption into polar solid-phase microextraction materials with ultrathin polydimethylsiloxane coating for thermal desorption-gas chromatography analysis.

Solid-phase microextraction (SPME) coupled with thermal desorption-gas chromatography (TD-GC) has become a powerful analysis tool for volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) in water samples. However, water adsorption into polar microextraction phase is usually unavoidable during the extraction process, and the burst of large amounts of water vapour during thermal desorption will cause serious problems to GC separation and detectors. Pawliszyn's group had demonstrated that the tens of micron-thick, defect-free polydimethylsiloxane (PDMS) coating could act as a perfect barrier for water adsorption and offer much better compatibility in complex matrices. However, the PDMS overcoat largely decreased the uptake rate of polar analytes into the inner sorbent. In order to quantify the effect of PDMS coating thickness on water adsorption amount and the extraction kinetics, ultrathin PDMS layer was used to coat the polar extraction phase with polyimide (PI) as a model in this work. It was surprising to find that the PDMS coating with the thickness less than one micron can decrease the water adsorption by 96%, while the extraction efficiency for polar analytes (phenolic compounds and nitroaromatic explosives) was decreased by less than 20% at the extraction time of 30 min. Moreover, the kinetic data showed that the thinner the PDMS coating was, the less the uptake rate of polar analytes into PI extraction phase decreased. Finally, polar poly (phthalazine ether sulfone ketone) (PPESK) extraction phase was also coated with ultrathin PDMS coating to verify the universality of the strategy. Generally, the water adsorption problem in polar SPME was overcome to a great extent, and the extraction efficiency of polar analytes was mainly preserved with this ultrathin PDMS coating, which could broaden the application of SPME in the environmental field.

Electrospun nanofiber cloud for ultrafast solid phase micro-extraction of trace organics in water samples.

In order to achieve ultrafast solid phase micro-extraction (SPME) of trace organics in water samples, the robust polyimide/polyvinylpyrrolidone (PI/PVP) composite nanofiber was prepared by electrospinning. Unlike the nonwoven electrospun membrane bulk widely used for SPME, the hydrophilic PI/PVP nanofibers here can be easily dispersed into and recovered from water sample like a cloud, so nanofiber cloud SPME (NC-SPME) was proposed in this work. The extraction performance of the NC-SPME method was evaluated using phthalates and organochlorine pesticides as model analytes. The extracted analytes were then desorbed by acetone and eventually quantified by gas chromatography-mass spectrometry (GC-MS). The extraction equilibrium was reached in 30 s for most of the phthalates and 2 min for organochlorine pesticides. While for bar-SPME, the equilibrium time was much longer than 2 h. At the extraction time of 5 min, the recoveries of phthalates and organochlorine pesticides were more than 34% and 52% by the NC-SPME method while they were less than 15% and 10% respectively by the bar-SPME method. In a word, the NC-SPME method presented significant advantages such as fast equilibrium and high recoveries compared to bar-SPME. For the phthalates analysis of real samples by NC-SPME, 5 mL of water sample was used for a 5-min extraction, linear range covered 1-2 orders of magnitude with correlation coefficients (r) higher than 0.99 and limits of detection (LODs) at ng/L levels for all of the tested water samples. This method will be useful for the rapid micro-extraction of other kinds of organics in water samples even biological fluid samples due to the stable composition, ultra-hydrophilic surface of PI/PVP nanofiber, and the biocompatible nature of PVP.