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A mathematical model for the formation of condensation aerosols from highly supersaturated vapor-air mixtures is presented. The model is suitable for systems with very high nucleation rates that result in aerosol mass densities >1 g/m3. It accounts for nucleation, non-isothermal condensation, coagulation and indirectly for coalescence of the newly formed particles. It applies kinetic theory to determine the nucleation rate and treats nucleation and coagulation in separate stages, but both are coupled with non-isothermal condensation. A statistical approach based on the Weibull function is used to estimate the size distribution of the droplets (particles). The model has been applied to study the formation of glycerol aerosols in Electronic Nicotine Delivery Systems. The model qualitatively reproduces the observed trend that the aerosol particle size decreases as the puff flow rate increases. Within the model framework, at lower puff flow rates higher particle concentrations occur leading to higher rates of coagulation which result in larger particle size aerosol. Copyright © 2021 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Measuring the aerosol particle size of electronic cigarettes can be particularly challenging due to the volatile and dynamic nature of these aerosols. In particular, electronic cigarette aerosol particle size measurements may be convoluted by evaporation due to the high dilution ratios and coagulation when there are long residence times between sampling and measurement. To address these measurement issues, we have developed a particle size measurement system using a low flow cascade impactor with a sampling system that is capable of generating a puff on an e-cigarette and directly introducing the aerosol into the inlet flow of the impactor. The system has been used to investigate factors that may affect the aerosol size distribution, including puffing conditions, carrier composition and device construction. It was found that decreasing the puff flow rate from 2 to 0.5 L/min at a constant puff duration of 5 s, the mass median aerodynamic diameter (MMAD) of the aerosol size distribution increased from 0.5 to 1.1 µm. Increasing the mass delivery from 0.67 to 6 mg/5 s puff also resulted in increasing MMAD from 0.48 to 0.87 µm. Furthermore, the addition of a small amount of glycerin (1% by weight) to a propylene glycol based flavor formulation caused a decrease in the MMAD, while the other factors studied did not have a significant effect on the MMAD. Copyright © 2020 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

This research was designed to investigate if antioxidant sulforaphane (SFN) alleviates methamphetamine (METH)-induced neurotoxicity by activation of the Nrf2-mediated pathway. Oxidative damage, apoptosis and mitochondrial membrane potential were evaluated in PC12 cells or the prefrontal cortex of SD rats post METH treatment with/without SFN. In addition, knockdown of Nrf2 expression in PC12 cells was used to further study the underlying mechanism. The results showed that METH exposure induced increased oxidative damage and apoptosis accompanied by decreased expressions of Nrf2, HO-1 and GCS in PC12 cells and the prefrontal cortex of SD rats. Meanwhile SFN effectively prevented METH-induced cell oxidative damage, apoptosis and mitochondrial membrane potential; however, the knockdown of Nrf2 expression partly reversed the protective effect of SFN in reducing METH-induced oxidative damage and apoptosis in PC12 cells. These results indicate that SFN might be a promising functional food-derived compound for preventing METH-induced neurotoxicity via the Nrf2-mediated pathway. [ABSTRACT FROM AUTHOR]

Tissue inhibitor of metalloproteinases (TIMPs) are endogenous inhibitors of matrix metalloproteinases that are involved in normal cellular processes and in the development and progression of atherosclerosis. Our purpose was to evaluate the polymorphisms of the TIMP-3 genes for their associations with carotid plaques or with serum protein levels in the Han Chinese population. Two promoter variants, −915A/G (rs2234921) and −1296T/C (rs9619311), were genotyped in 548 subjects with no plaques, 462 subjects with echogenic plaques, and 427 subjects with mixture plaques. The serum TIMP-3 levels were measured using an enzyme-linked immunosorbent assay (ELISA). There was a strong linkage disequilibrium between −1296T/C and −915A/G (D′ = 1.0, r2 = 0.991). The individuals with the genotype (TC+CC) were 1.8 times more likely to have mixture plaques than the individuals with the TT genotype (P = 0.001, OR: 1.836, 95%CI: 1.269-2.665). The frequency of the C allele in the mixture plaque group was significantly higher than in the no plaque group (P = 0.009, CI: 1.119-2.187). We observed a significant elevation of the TIMP-3 levels in the serum of patients affected with mixture plaques compared to those with no plaques (P = 0.013). The current data suggest that genetic variation in the TIMP-3 genes may contribute to individual differences in mixture plaque susceptibility in the Han Chinese population. [ABSTRACT FROM AUTHOR]

The polarization ratio method is used for fast in-situ characterization of unimodal condensed aerosols of e-cigarettes. The method is based on 90°-light scattering of polarized 680 nm laser light by the droplet ensemble inside an optically defined measuring volume. Mass median droplet diameter (MMD) is derived from the ratio of scattered light from horizontally and vertically polarized incident light beams assuming a fixed value of the geometric standard deviation of the aerosol mass distribution. MMD is used to correct for the size dependence of the mass-based scattering signal of vertically polarized light to obtain the mass concentration if the sensor is calibrated once with an aerosol with a fixed MMD. The sensor uses commercially available aerosol photometers, and its application to e-cigarette aerosols was validated with an impactor for MMD and with a filter measurement for mass concentration. Good correlation (r2 > 0.97) for both parameters was observed. Application ranges are mass concentration range 0.5-50 mg/L, MMD 0.2-1.2 µm, 100 ms time resolution, and 0.2-3 L/min flow rate. The usefulness of this simple sensor for e-cigarette aerosol characterization is demonstrated by developing a scaling law between MMD and operating parameters of an e-cigarette, i.e., puff flow rate and mass concentration. Copyright © 2018 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

A new DMA column has been designed with the capability of simultaneously extracting monodisperse particles of different sizes in multiple stages. We call this design a multistage DMA, or MDMA. A prototype MDMA has been constructed and experimentally evaluated in this study. The new column enables the fast measurement of particles in a wide size range, while preserving the powerful particle classification function of a DMA. The prototype MDMA has three sampling stages, capable of classifying monodisperse particles of three different sizes simultaneously. The scanning voltage operation of a DMA can be applied to this new column. Each stage of MDMA column covers a fraction of the entire particle size range to be measured. The covered size fractions of two adjacent stages of the MDMA are designed somewhat overlapped. The arrangement leads to the reduction of scanning voltage range and thus the cycling time of the measurement. The modular sampling stage design of the MDMA allows the flexible configuration of desired particle classification lengths and variable number of stages in the MDMA. The design of our MDMA also permits operation at high sheath flow, enabling high-resolution particle size measurement and/or reduction of the lower sizing limit. Using the tandem DMA technique, the performance of the MDMA, i.e., sizing accuracy, resolution, and transmission efficiency, was evaluated at different ratios of aerosol and sheath flowrates. Two aerosol sampling schemes were investigated. One was to extract aerosol flows at an evenly partitioned flowrate at each stage, and the other was to extract aerosol at a rate the same as the polydisperse aerosol flowrate at each stage. We detail the prototype design of the MDMA and the evaluation result on the transfer functions of the MDMA at different particle sizes and operational conditions. [ABSTRACT FROM AUTHOR]

A new deconvolution scheme is proposed to retrieve the true transfer function of differential mobility analyzers (DMAs) from tandem DMA (TDMA) experimental data. Apart from the existing methods in which the transfer function is represented as either a triangular or a Gaussian shape, the true DMA transfer function in the new scheme is represented by a piecewise linear function. The conjugate gradient optimization method is used to find the best fit between the calculated and experimental TDMA data. It is shown that the scheme is insensitive to experimental error and able to differentiate the shapes of DMA transfer functions for different particle sizes. The scheme is further applied to obtain the true transfer function of Nano-DMA (Chen et al. 1998). [ABSTRACT FROM AUTHOR]