Search

Silicon‐containing arylacetylene resin (PSA)‐matrix composites hold great potential for aerospace applications due to their excellent heat resistance. In recent years, many PSAs with specific functions have been designed via materials genome approach (MGA), and appropriate resin transfer molding (RTM) curing processes need to be screened to strike a balance between low cost and high quality. In this study, a novel tool based on finite element curing simulation and multiobjective genetic algorithm was developed to optimize the RTM curing process for novel PSA‐matrix composites. The silicon‐containing fluorenylacetylene resin (PSA‐VBF) was selected as the object to systematically characterize its apparent curing kinetics. To address the problem of explosive polymerization of the resin at the injection port during the RTM process, a multiobjective optimization of the curing process using a genetic algorithm was performed to obtain the Pareto front with the maximum temperature gradient at the injection port of the resin, the maximum degree of cure gradient of the composites, and the process time as the objectives. A global sensitivity analysis was also conducted to identify the key parameters. The results demonstrate that the optimized curing process can significantly reduce the temperature gradient and the curing degree gradient with improved curing efficiency. [ABSTRACT FROM AUTHOR]

Timely and accurate detection of water pipe leakage is critical to preventing the loss of freshwater and predicting potential hazards induced by the change in underground water conditions, thereby developing mitigation strategies to improve the resilience of pipeline infrastructure. Ground‐penetrating radar (GPR) has been widely applied to investigating ground conditions and detecting pipe leakage. However, due to uncertainties of complex underground environments and time‐lapse change, a proper interpretation of GPR data has been a challenging task. This paper aims to leverage hydromechanical (HM) modelling to predict electromagnetic (EM) responses of water leakage detection in diverse leakage cases. A high‐fidelity 3D digital model of an actual pipeline network, hosting pipes with various sizes and materials, was reconstructed to represent the complex geometry and various mediums. The interoperability between the digital model and the numerical models utilized in HM and EM simulations was improved to better capture the irregular pipelines. Based on Kriging interpolation and the volumetric complex refractive index model, a linking technique was employed to replicate material heterogeneity caused by water intrusion. Thus, a framework was developed to accommodate the interoperability among digital modelling, HM modelling and finite‐difference time‐domain forward modelling. Moreover, sensitivity studies were conducted to evaluate the influences of different time stages, leak positions and pipe types on GPR responses. In GPR B‐scans, the presence of hyperbolic motion and horizontal reflections serve as indicators to estimate the location and scale of water leakage. Specifically, a downward‐shifting hyperbola indicates that the pipeline is submerged by leaked water, whereas the emergence of horizontal reflection is linked to the wetting front of saturated areas. The developed framework can be expanded for complicated applications, such as unknown locations and unforeseen failure modes of pipelines. It will increase the efficiency and accuracy of traditional interpretations of GPR‐based water leakage detection and thus enable automated interpretations by data‐driven methods. [ABSTRACT FROM AUTHOR]

Background: Men who have sex with men (MSM) face significant risks of Chlamydia trachomatis (CT) and/or Neisseria gonorrhoeae (NG) infection. Nevertheless, only limited studies have looked into the site-specific infection and clearance of CT/NG. In order to prevent transmission, it is essential to understand the underlying factors that drive infection and spontaneous clearance., Methods: A 12-week cohort study examined the association between CT/NG infection, self-clearance, and sexual behaviors among MSM. The Willingness Service recruited participants who completed weekly questionnaires and provided urine, throat, and rectal swab samples., Results: The study involved 151 men, in which 51 (33.8%) were diagnosed with CT/NG infection during the study period. HIV (OR = 11.31), kissing (OR = 1.59), receptive oral sex (OR = 36.64), and insertive anal sex (OR = 19.73) constituted significant risk factors. 100% condom use (OR = 5.78) and antibiotic (OR = 7.53) were more likely to cause spontaneous clearance., Discussion: MSM may engage in riskier sexual behaviors due to insufficient knowledge and awareness of STI prevention, leading to increased susceptibility to NG/CT. It is crucial to concentrate on enhancing health education for MSM., Conclusion: This study found that the rectum was the most prevalent site of CT/NG and sexual behavior can influence the infection. Additionally, the appropriate use of antibiotics and consistent condom use may contribute to clear spontaneously., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer PZ declared a shared affiliation with the author WT to the handling editor at the time of review., (Copyright © 2024 Lyu, Tang, Feng, Hu, Wang, Zhou, Huang, Li, Zhu, He, Tang, Zhou and Zhang.)

A poly(methyl methacrylate)-supported Pd 0 nanocatalyst was successfully prepared from solution reaction of Pd(CH 3 COO) 2 with a copolymer acid, poly(methyl methacrylate- ran -methacrylic acid) (MMA-MAA). The reaction was carried out in a benzene/methanol mixed solvent in the dark at room temperature (∼25 °C) in the absence of a typical chemical reductant. There was coordination between the Pd 0 nanoclusters and MMA-MAA, resulting in Pd 0 nanoclusters being stably and uniformly dispersed in the MMA-MAA matrix, with an average particle size of ∼2.5 ± 0.5 nm. Mechanistically, it can tentatively be proposed that PMMA-ionomerization of the Pd 2+ ions produces intramolecular -2COO - -Pd 2+ aggregate cross-links in the solution. On swelling of the chain-segments that are covalently bound via multiple C-C bonds, the resultant elastic forces cause instantaneous dissociation at the O-Pd coordination bonds to give transient bare ( i.e. , uncoordinated), highly-oxidative Pd 2+ ions and H + -associative carboxylate groups, both of which rapidly scavenge electrons and protons, respectively, of the active α-H atoms abstracted from the methanol molecules of the solvent to make Pd 0 nanoclusters supported by the re-formed MMA-MAA. The MMA-MAA acid copolymer, without itself undergoing any permanent chemical change, serves as a mechanical activator or catalyst for the mechanochemical reduction of Pd(CH 3 COO) 2 under mild conditions. Compared with traditional Pd/C catalysts, this Pd 0 nanocatalyst exhibited more excellent catalytic efficiency and reusability in the Heck reaction between iodobenzene and styrene, and it could be easily separated. The supported Pd 0 nanocatalyst prepared using this novel and simple preparation method may display high-efficiency catalytic properties for other cross coupling reactions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)