Particle shape plays an essential role in deformation characteristics of railway ballast bed. The numerical reconstruction of ballast morphological features, including overall shape and angular distribution, remains a hot issue in research on ballast mechanical behavior simulation. A novel shape reconstruction method was adopted to generate ballast particles that met the desired probability density distribution of morphological indices. On this basis, the numerical model of ballast triaxial tests were established under different confining pressures. The results were compared with those obtained from indoor tests and simulations whose particles were generated from 3D scanning or non-statistical random generation. The results show that the particle shape has a growing effect on the mechanical response of ballast, with an increase in confining pressure. The relation between deviatoric stress and axial strain in the specimen which meets the probability density distribution is more consistent with the experimental results than that of the non-statistical randomly generated specimen. The lateral deformation of ballast is correlated with the adjustment of the packing structure. For non-statistical randomly generated specimen, both the lateral deformation and the particle adjustment are larger than those generated by 3D scanning. The ballast contact force evolution is less influenced by its morphological features. Nevertheless, the difference in the maximum contact force of specimens with various particle shapes is nearly 50%.

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The high chlorine dosages in wastewater treatment plants during the COVID-19 pandemic may result in increased formation of disinfection by-products (DBPs), posing great threat to the aquatic ecosystem of the receiving water body and the public health in the downstream area. However, limited information is available on the effect of biological wastewater treatment processes on the formation of CX3R-type DBPs. This study investigated the effect of oxidation ditch (OD) and anaerobic-anoxic-oxic (AAO), two widely used biological wastewater treatment processes, on the formation of five classes of CX3R-type DBPs, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetaldehydes (HALs), haloacetonitriles (HANs) and halonitromethanes (HNMs), during chlorination. Experimental results showed that biological treatment effectively reduced the dissolved organic carbon (DOC) and UV254, while it increased the dissolved organic nitrogen (DON), and therefore the ratio of DON/DOC. In addition, increases in the contents of soluble microbial product- and humic acid-like matters, and the transformation of high molecular weight (MW) fractions in the dissolved organic matter into low MW fractions were observed after OD and AAO processes. Although biological treatment effectively decreased the formation of Cl-THMs, Cl-HAAs, Cl-HANs and Cl-HNMs, the formation of DBCM, DBAA, BDCAA, DBCAA, DCAL, TCAL and DBAN (where C = chloro, B = bromo, D = di, T = tri) all increased significantly, due to the increased formation reactivity. Moreover, biological treatment increased the ratio of bromide/DOC and bromine incorporation into THMs, HAAs and DHANs except for HALs and THANs. Different from previous studies, this study revealed that biological treatment increased the formation of some DBPs, especially brominated DBPs, despite the efficient removal of organic matters. It provides insights into the DBP risk control in wastewater treatment, particularly during the COVID-19 pandemic.@en

The morphology, size, and surface properties of pharmaceutical particles form an essential role in the therapeutic performance of active pharmaceutical ingredients (APIs) and excipients as constituents in various drug delivery systems and clinical applications. Recent advances in methods for surface modification, however, rely heavily on liquid-phase-based modification processes and afford limited control over the thickness and conformality of the coating. Atomic layer deposition (ALD), on the other hand, enables the formation of conformal nanoscale films on complex structures with thickness control on the molecular level, while maintaining the substrate particle size and morphology. Moreover, this enables nanoengineering of surfaces of pharmaceutical particles also in the dry state. Successful nanoengineeering of crystal and amorphous surfaces of pharmaceutical particles is demonstrated in this study whereby functional properties, such as dissolution and dispersibility, were tailored for drug delivery applications. This expands on our initial work on ALD of alumina on pharmaceutical particles within the lower micro- to higher nanosize ranges to here probe both crystalline and amorphous lactose substrate surfaces (d₅₀ = 3.5 and 21 μm). In addition, both water and ozone coreactants were evaluated, the latter having not been evaluated previously for pharmaceutical particles. The deposition process is carried out at ambient conditions in a fluidized bed reactor for a low number of cycles (i.e., from 4 to 14). Improved dissolution and extended release were achieved by the ALD nanoengineering of both crystalline and amorphous surfaces. This novel concept opens up exciting opportunities to produce more complex materials and structures using temperature- and moisture-sensitive drugs, e.g., targeting and drug delivery opportunities, as well as delivering new functionalities for novel applications in the pharmaceutical, medical, biological, and advanced materials fields. The prospects for advancing inhaled drug delivery are exemplified by the ALD surface nanoengineering concept.

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Atmospheric particulate matter (PM) can be scavenged by rainfall and contribute dissolved organic matter (DOM) to rainwater. Rainwater may serve as a part or the whole of drinking water sources, leading to the introduction of PM-derived DOM into drinking water. However, little information is available on the role of PM-derived DOM as a remarkable precursor of CX₃R-type disinfection by-products (DBPs) in rainwater. In this study, samples were collected from ten occurrences of rainfall in Shanghai and batch experiments were executed to explore the contribution of PM-derived DOM to CX₃R-type DBP formation in rainwater and to further understand some of unknowns regarding its characteristics. Results revealed that a part of PM was scavenged by rainfall and the scavenge performance was better for smaller PM. The formation potentials (FPs) of individual CX₃R-type DBP were similar among size-isolated PM. TCM was predominant (around 0.5–4.5 μg-C/mg-C) and TCAA was the secondary (around 0.6–3.2 μg-C/mg-C) among all detectable CX₃R-type DBPs. Based on the PM removal data and DBP FP results, the contribution of PM-derived DOM to CX₃R-type DBP formation in rainwater was modeled. Furthermore, aromatic proteins and soluble microbial product-like compounds were found to be significant compositions, which were reported to be DBP precursors. And low molecular weight (< 10 kDa) DOM derived from total PM and rainwater exhibited higher CX₃R-type DBP FPs. DOM fractions with higher SUVA₂₅₄ and SUVA₂₈₅ values gave relatively higher yields of CX₃R-type DBPs, indicating that aromatic compounds played an important role in DBP formation.

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