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The heterocharge accumulated in the oil‐paper insulation system of the converter transformer will enhance the local electric field and cause insulation deterioration. Numerical simulation is an effective method to analyze heterocharge. Currently, the numerical simulation of heterocharge is mainly based on the bipolar charge transport (BCT) model and the impurity ion transport (IIT) model. However, the effects of temperature, conductivity, and thickness of oil‐impregnated paper on charge transport have not been considered in these models. In view of this, a modified charge transport (MCT) model by introducing the Maxwell–Wagner model and heat conduction equation is proposed in this paper based on the BCT model and IIT model. Then, the influence of multi‐factors (temperature gradient, moisture content, and oil‐impregnated paper thickness) on heterocharge accumulation is investigated by using the MCT model. The simulation results obtained by the MCT model are more consistent with the experimental results than the BCT model, which proves the accuracy and superiority of the MCT model. Moreover, the increase in temperature gradient, moisture content, and oil‐impregnated paper thickness will enlarge the ion dissociation rate, conductivity, and trap density, and thus promote the generation of heterocharge. In that respect, the MCT model is expected to optimize the insulation design and provide a reference for space charge dynamic simulation. [ABSTRACT FROM AUTHOR]

The accuracy and feasibility of the traditional XY model of transformer oil–paper insulation system are disputable since it ignored the effect of non‐uniform aging and conductance on dielectric response property. Given this issue, this work attempted to report a modified XY model to overcome these defects. The novelty of this work is in the exploration of the modified XY model as a potential tool for establishing the quantitative correlation among the complex relative permittivity of the liquid insulation, solid insulation, and liquid–solid composite insulation. In that respect, the presented verification experiments proved the feasibility and accuracy of the reported model. The contributions are expected to provide a theoretical basis for the condition evaluation of transformer solid insulation under non‐uniform aging conditions. [ABSTRACT FROM AUTHOR]

Accumulating evidence has suggested that extracellular vesicles (EVs) play a crucial role in lung cancer treatment. Thus, we aimed to investigate the modulatory role of bone marrow mesenchymal stem cell (BMSC)‐EV‐derived let‐7i and their molecular mechanism in lung cancer progression. Microarray‐based analysis was applied to predict lung cancer‐related miRNAs and their downstream genes. RT‐qPCR and Western blot analyses were conducted to determine Let‐7i, lysine demethylase 3A (KDM3A), doublecortin‐like kinase 1 (DCLK1) and FXYD domain‐containing ion transport regulator 3 (FXYD3) expressions, after which dual‐luciferase reporter gene assay and ChIP assay were used to identify the relationship among them. After loss‐ and gain‐of‐function assays, the effects of let‐7i, KDM3A, DCLK1 and FXYD3 on the biological characteristics of lung cancer cells were assessed. Finally, tumour growth in nude mice was assessed by xenograft tumours in nude mice. Bioinformatics analysis screened out the let‐7i and its downstream gene, that is KDM3A. The findings showed the presence of a high expression of KDM3A and DCLK1 and reduced expression of let‐7i and FXYD3 in lung cancer. KDM3A elevated DCLK1 by removing the methylation of H3K9me2. Moreover, DCLK1 suppressed the FXYD3 expression. BMSC‐EV‐derived let‐7i resulted in the down‐regulation of KDM3A expression and reversed its promoting role in lung cancer development. Consistently, in vivo experiments in nude mice also confirmed that tumour growth was suppressed by the BMSC‐EV‐derived let‐7i. In conclusion, our findings demonstrated that the BMSC‐EV‐derived let‐7i possesses an inhibitory role in lung cancer progression through the KDM3A/DCLK1/FXYD3 axis, suggesting a new molecular target for lung cancer treatment. [ABSTRACT FROM AUTHOR]

In recent years, MXene has become a hotspot because of its good conductivity, strong broadband absorption, and tunable band gap. In this contribution, 0D MXene Ti3C2Tx quantum dots are synthesized by a liquid exfoliation method and a wideband nonlinear optical response from 800 to 1550 nm is studied, which have a larger nonlinear absorption coefficient β of –(11.24 ± 0.14) × 10–2 cm GW–1. The carrier dynamic processes of 0D MXene are explored with ultrahigh time resolution nondegenerate transient absorption (TA) spectroscopy, which indicates that the TA signal reaches its maximum in 1.28 ps. Furthermore, 0D MXene is used to generate ultrashort pulses in erbium or ytterbium‐doped fiber laser cavity. High signal‐to‐noise (72 dB) femtosecond lasers with pulse durations as short as 170 fs with spectrum bandwidth of 14.8 nm are obtained. Finally, an ultranarrow fiber laser based on 0D MXene is also investigated and has a full width at half maximum of only 5 kHz, and the power fluctuation is less than 0.75% of the average power. The experimental works prove that 0D MXene is an excellent SA and has a promising application in ultrafast and ultranarrow photonics. [ABSTRACT FROM AUTHOR]

The ageing rate of cellulose insulation materials (paper/pressboard) in oil‐impregnated transformers is largely determined by moisture. In this paper, several experiments were conducted under controlled laboratory conditions to quantitatively diagnose the amount of moisture in cellulose insulation using frequency domain spectroscopy (FDS) technique, which has been proven to be an effective tool to predict the insulation condition in oil‐impregnated power equipment. The frequency dielectric response in oil‐impregnated pressboards, moisture content as well as test temperature, was monitored carefully, and a new dielectric characteristic parameter for the diagnosis of moisture content was proposed. In addition, the master curve technique was introduced to calibrate the temperature effect on FDS measurement results. These experiments revealed that a strong correlation exists between frequency dielectric parameter and moisture content in cellulose insulation. Such correlation can be utilised for better prediction of moisture content in paper–oil insulation. A modified assessment method for the diagnosis of moisture content in paper–oil insulation was investigated and its effectiveness was also demonstrated using a case. [ABSTRACT FROM AUTHOR]

Photodetectors fabricated from very thin two‐dimensional (2D) materials with high photoelectric conversion efficiency have unprecedented potential to overcome the limitations of conventional photodetectors. In particular, recent interest in 2D metal phosphorus trichalcogenides (MPTs) has derived from their strong light absorption, tunable bandgap, and robust stability. Here, large and atomically thin NiPS3 flakes, prepared by electrochemical cathodic exfoliation, are used as electrodes for a self‐powered photo‐electrochemical (PEC) detector. It exhibits high photocurrent density, sensitive responsivity, cycling stability, and excellent on/off behavior under sunlight in a 0.1 m KOH solution. The KOH concentration and the external potential affect the performance, indicating that it can be an excellent PEC‐type detector. This work provides fundamental knowledge about PEC‐type MPT photodetectors and reveals the great potential of NiPS3 as an optoelectronic device. [ABSTRACT FROM AUTHOR]