In this report, β‐cyclodextrin (β‐CD)‐functionalized silica nanoparticles (SNPs) with dendrimer‐like spacers were synthesized by first grafting the SNPs with different generations of polyamidoamines ...(PAMAMs), followed by modifying the grafted SNPs with mono‐6‐deoxy‐(p‐tolylsulfonyl)‐β‐CD. The β‐cyclodextrin‐modified silica nanoparticle‐cored PAMAMs (SNP‐PAMAM‐β‐CDs) were studied as chiral pseudostationary phases for separating three racemic drugs, namely, chlorpheniramine, nefopam, and verapamil. The β‐CD‐functionalized SNPs with dendrimer‐like spacers were more enantioselective than native β‐CD, and the structures of the dendritic spacers were highly influential on the separation. In 20 mM NaH2PO4, addition of 4.00 mg/mL SNP‐G1.0‐β‐CD (corresponding to 1.12 mM β‐CD) could baseline separate the enantiomers of chlorpheniramine and nefopam, and introduction of 7.00 mg/mL SNP‐G0‐β‐CD (corresponding to 1.68 mM β‐CD) resulted in enantioseparation of the verapamil racemates. On the contrary, the enantiomers of nefopam and verapamil could not be resolved in the presence of 15 mM native β‐CD. Our results suggest that SNP‐PAMAM‐β‐CDs hold great promise for enantioselective separations.
An experimental study was conducted to investigate the discharge characteristics of short air gap and insulation surface under flame conditions. The influence of ac electric field on flame and the ...mechanism leading to the reduction of breakdown voltage under flame conditions are analyzed. Results show that under the ac electric field, the flame is deflected to the high voltage electrode, and compared with normal conditions (without flame), the breakdown voltage of the short air gap and the insulation surface is decreased by 74.4% and 70%, respectively. Besides, arc levitation appears at high probability under the flame conditions. Furthermore, the decrease of the breakdown voltage of short air gap and the flashover voltage of insulation surface under the flame conditions are mainly due to the increase of the air conductivity and the decrease of the air density. For the insulating dielectric, the change of the flashover path is also one of the main reasons for the decrease of the flashover voltage.
Photopolymerization-based 3D printing has emerged as a key technology in hydrogel manufacturing, broadening the attributes of hydrogels and extending their applications into diverse engineering ...fields. However, the mechanical properties of hydrogels dramatically impact the functionality and quality in practice. It is necessary to develop an appropriate theoretical model to predict the evolution of the mechanical properties of hydrogels during the photopolymerization process. In this work, systematical experiments were performed to investigate mechanical properties of PAAm hydrogel under different photopolymerization condition. The results reveal a noticeable increasement in both elastic and viscous behavior of hydrogel with the advancement of polymerization. To fully capture the experimental observations, we developed a coupled photo-chemo-mechanical theoretical framework that integrates reaction kinetics with a physically-based viscoelastic constitutive model. Within this model, the degree of conversion serves as an internal variable, which related to microscopic structures such as correlation length, and tube diameter. The developed model exhibits remarkable prediction ability for hydrogels with various degree of polymerization. The current work paves a potentially new avenue for understanding the evolution of mechanical properties in photopolymerized hydrogels, providing theoretical guidance for the manufacturing of hydrogels through photopolymerization-based 3D printing.
•Ginsenoside Rg3 weakened AngⅡ-induced myocardial hypertrophy and fibrosis.•Rg3 inhibited the levels of NLRP3 inflammasome and oxidative stress in cardiomyocytes.•Rg3 regulated the SIRT1/NF-κB ...signaling pathway.•Rg3 attenuated the progression of myocardial hypertrophy in vivo.
Ginsenoside Rg3 (Rg3), one of the most potent components extracted from the roots of the traditional Chinese herb Panax ginseng, has prominent roles in anti-tumor and anti-inflammation. However, the applications of Rg3 against myocardial hypertrophy are not fully revealed.
Transverse aortic constriction (TAC) was adopted to build the myocardial hypertrophy model in rats. The in vitro model of myocardial hypertrophy was induced by angiotensin II (Ang II) in the human cardiomyocyte cell line AC16 and HCM, which were then treated with different doses of Rg3. The levels of myocardial hypertrophy markers (ANP, BNP, and β-MHC) were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Western blot (WB) was conducted to verify the expressions of myocardial fibrosis-associated proteins (MyHc, Collagen Ⅰ, and TGF-β1) and oxidative stress (OS) proteins (HO-1 and Nrf2). The markers of fibrosis, hypertrophy, NLRP3 inflammasome and OS in cardiomyocytes were evaluated by qRT-PCR, western blot (WB), enzyme-linked immunosorbent assay (ELISA), and cellular immunofluorescence, respectively. Furthermore, pharmacological intervention on sirtuin-1 (SIRT1) was performed to clarify the function of SIRT1 in Rg3-mediated effects.
Rg3 dose-dependently attenuated the Ang II-induced myocardial hypertrophy and fibrosis. What’s more, Rg3 markedly inhibited NLRP3-ASC-Caspase1 inflammasome and OS (reflected by SOD, MDA, HO-1, and Nrf2) in cardiomyocytes treated with Ang II. Mechanistically, Rg3 attenuated NF-κB activation and promoted SIRT1 expression. Inhibiting SIRT1 (by AGK2) mostly reversed Rg3-mediated effects against Ang II-induced myocardial hypertrophy and fibrosis. In the TAC rat model, administration of Rg3 mitigated myocardial hypertrophy and fibrosis through pressing overproduced inflammation and OS.
Rg3 prevents Ang II-induced myocardial hypertrophy via inactivating NLRP3 inflammasome and oxidative stress by modulating the SIRT1/NF-κB pathway.
Knowing more about insulator pollution is of guiding significance to the development of anti-pollution strategies. Traditional methods can be used to determine only the pollution degree of ...insulators. However, the pollution distribution also has a substantial influence on the flashover voltage of insulators even under the same equivalent salt deposit densities (ESDD). In this article, an ESDD spectral density method and a visualization method based on hyperspectral technology are proposed. The proposed method presents the ESDD distribution using hyperspectral images. A detection model based on characteristic wavelengths is established with partial least squares regression to detect the insulator ESDDs. Based on the ESDD detection results, the features of the ESDD spectral density process, including the building of the ESDD probability graph, the overall ESDD, and visualization of the ESDD, are presented. Example analyses of field-operating insulators were conducted, revealing that the ESDD spectral density can be used to track the pollution distribution of insulators and that the pollution degree can be calculated from the overall ESDD. The error of the overall ESDD calculated by this method is within 10%. In addition, visualization of the pollution distribution can more intuitively record the degree of pollution and the nonuniform distribution characteristics. Both the pollution degree and distribution can be obtained by this method. Therefore, hyperspectral technology can overcome the limitations of traditional methods and convert the ESDD results into an image to determine the ESDD distribution. These research results provide theoretical instruction for guiding insulation design and anti-pollution strategies for operating transmission lines.
•Effect of biomass ash on the sintering of Mn-based OC is revealed by TMA.•Apparent activation energy of the sintering (Es) of Mn-based OC is studied.•The liquid sintering rate of Mn-based OC is ...closely related to slag content.•Es of high-Mn OC is increased to 93–107 kJ/mol due to biomass ash addition.•Ca promotes OC expansion by improving Mn-based mineral crystallization.
The Mn-based oxygen carrier (OC) owns a great oxygen carrying capacity and a high reactivity in the chemical looping gasification of biomass. However, the sintering of the Mn-based OC can cause serious defluidization or even the shut-down of the biomass chemical looping gasifier. In this study, the sintering kinetics and mechanism of Mn-based OC in the gasification of two typical biomass ash were revealed by thermomechanical and thermodynamic analysis. It revealed that the manganese silicate was converted to iwakiite (MnFe2O4) and liquid at high temperatures in the high-Mn OC (OC2), leading to the liquid sintering mechanism and high apparent activation energy of sintering (Es), with a maximum shrinkage rate of 6.14 %/oC. Conversely, the solid sintering mechanism of the low-Mn OC (OC1) was attributed to the FeMn2O4 crystallization, leading to a low shrinkage rate (The maximum shrinkage rate was 0.30 %/oC). The sintering rate of Mn-based OC was closely related to the liquid content, and the biomass ash addition advantaged the liquid formation. Therefore, the Es of OC1 was increased from 44 kJ/mol to 151 kJ/mol at the 15 wt% addition of corn straw ash, and Es of OC2 was increased from 72 kJ/mol to 93–107 kJ/mol at 20 wt% addition of biomass ash. Element distribution analysis supported that Ca in sawdust ash improved the bonding between Mn and Si, improving the Mn-based minerals crystallization and OC expansion. However, the K in corn straw ash facilitated the melting of rhodonite(MnSiO3), and the expansion of Mn-based OC was inhibited. This study provides valuable insights into the sintering mechanism of the Mn-based oxygen carrier and its relationship with liquid evolution behavior in the chemical looping gasification of biomass.
Composite insulators are integral to the power grid, providing electrical insulation and mechanical support. However, their prolonged exposure to outdoor conditions renders them vulnerable to ageing. ...This can result in flashovers and economic losses. Hyperspectral imaging (HSI) has been identified as a promising non-contact detection method to effectively assess the microscopic ageing status of these insulators’ surfaces. This study involved conducting artificial accelerated ageing experiments to mimic extended outdoor operational conditions. The static contact angle of ageing silicone rubber samples served as the basis for ageing classification. High-resolution HSIs of samples at various ageing stages were obtained, covering wavelengths from 400 nm to 1040 nm. Singular spectrum analysis was applied to denoise spectral and spatial domains, eliminating environmental and equipment-related noise effectively. Additionally, a convolutional neural network (CNN) was utilised to extract deep features from the spectral domain and combine them with spatial domain features, thus reducing dimensionality. The resulting fused spatial–spectral features were classified using a support vector machine. The joint denoising and feature fusion in this study’s spectral–spatial domain resulted in a notable improvement of 34.9 % in overall accuracy, achieving a score of 98.3 %. This approach exhibited superior performance, particularly in evaluating severely aged samples. The proposed approach enhances the accuracy in assessing the ageing status of composite insulators and enables pixel-level visualisation of ageing distribution. This assists in guiding the design of insulators’ shapes and materials for various environmental conditions. Moreover, this method is potentially applicable in detecting ageing in other electrical equipment.
The acidic environment is one of the main factors leading to the aging of silicone rubber (SiR) insulators. Aging can reduce the surface hydrophobicity and pollution flashover resistance of ...insulators, threatening the safe and stable operation of the power grid. Therefore, evaluating the aging state of insulators is essential to prevent flashover accidents on the transmission line. This paper is based on an optical hyperspectral imaging (HSI) technology for pixel-level assessment of insulator aging status. Firstly, the SiR samples were artificially aged in three typical acidic solutions with different concentrations of HNO
, H
SO
, and HCl, and six aging grades of SiR samples were prepared. The HSI of SiR at each aging grade was extracted using a hyperspectral imager. To reduce the calculation complexity and eliminate the interference of useless information in the band, this paper proposes a joint random forest- principal component analysis (RF-PCA) dimensionality reduction method to reduce the original 256-dimensional hyperspectral data to 7 dimensions. Finally, to capture local features in hyperspectral images more effectively and retain the most significant information of the spectral lines, a convolutional neural network (CNN) was used to build a classification model for pixel-level assessment of the SiR's aging state of and visual prediction of insulators' defects. The research method in this paper provides an important guarantee for the timely detection of safety hazards in the power grid.
PDF
