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Khat is a kind of common drug plant. Many experiments have shown that the content of cathinone norpseudoephedrine and norephedrine in some varieties of Khat are similar. However, some studies showed that there are differences in the intensity of psychoactivity between these varieties. Therefore, it is speculated that other substances in Khat may affect the psychoactive strength of Khat. But currently there are some difficulties in non-targeted screening of unknown compounds without mass spectrometry database information and standard solutions. In this paper, the unknown cathinone alkaloids in Khat were discovered and resolved by HPLC-Q-TOF MS in-source fragmentation multistage mass spectrometry. The separation was carried out on a ZORBAX Eclipse Plus Phenyl-Hexyl column (3.0 mm×100 mm×1.8 μm) with a gradient elution using 0.1% formic acid in water (A)-acetonitrile (B) as the mobile phase. The mobile phase flow rate was 0.3 mL/min, and the column temperature was 30 ℃. The screening of unknown cathinone alkaloid components was realized by the in-source cleavage characteristics of cathinone alkaloids in single-stage mass spectrometry under full-scan mode using an ESI ion source, and then the molecular structures of the unknown cathinone alkaloid components were deduced from the multi-stage MS cleavage patterns of the unknown cathinone alkaloid components in the target ion acquisition mode. The results showed that this method can effectively realize the screening and resolution of the unknown alkaloid components in Khat. A total of three cathinone alkaloid components, including methcathinone, ethcathinone and 2-amino-1-phenyl-1-butanone, were identified in Khat. Methcathinone and ethcathinone were corroborated using standard substances, and 2-amino-1-phenyl-1-butanone needs to be further corroborated due to the lack of corresponding standard substances. The work provides a guideline for the further study of the psychoactive components in Khat, and a reference for the analysis of unknown compounds in other fields.

The disconnector fault in gas insulated switchgear (GIS) is commonly caused by the combined effects of mechanical, thermal, and electrical factors. Throughout the progression from defect development to a severe fault, various signals, including abnormal vibration, temperature changes, and partial discharge, are generated. The simultaneous measurement and analysis of multi-parameter information pertaining to the GIS disconnector are crucial for accurately determining its operating condition. This study focuses on simulating typical defects in a 220 kV GIS disconnector to investigate the evolution patterns of vibration signals, temperature variations, and partial discharge signals under different contact states. The aim is to establish the correlation between these signals and the condition of the GIS disconnector. Additionally, the study proposes a comprehensive evaluation method for GIS disconnector by incorporating the health index theory and an improved analytic hierarchy process. The proposed method is subsequently applied to practical GIS, demonstrating consistency between the identified fault and the analysis results obtained through the multi-parameter comprehensive evaluation approach. Overall, this research introduces a highly feasible new method for the detection of GIS disconnector conditions.

The current research mainly focuses on the influence of different voltage forms on partial discharge for the interturn insulation of a transformer, and the discharge characteristics and its mechanism of interturn insulation under the action of preload are unclear. Therefore, a partial discharge test platform under the synergistic action of preloading force and electrical stress is constructed based on the actual operation conditions of the interturn insulation of a 750 kV transformer. Then, the partial discharge characteristics and its mechanism is explored by using (OM, SEM, FTIR, XRD, EDS, FEA). It is found that the statistical parameters and damage degree of interturn insulation decrease first and then increase with the increase in preload. Moreover, there is an inflection point at 1000 N. The reason is that the preload causes the deformation of the holes and air gaps between the layers of insulating paper and in the insulating paper. As a result, the contact area and volume of partial discharge are changed, which further changes the characteristics of partial discharge for interturn insulation. This study can provide a reference for the maintenance and structural optimization of 750 kV transformers. [ABSTRACT FROM AUTHOR]

Transformer oil plays the role of heat dissipation and insulation in power transformers, and its electrical and thermal characteristics are directly related to the stable operation of the transformer. At the same time, it is important to master the electric–thermal characteristics of transformer oil for transformer state evaluation, latent fault prediction, and maintenance planning. Based on this, the gas production rule and electrical characteristics of transformer oil under accelerated aging are studied in this paper. First, the experimental platform for power transformer aging is established to accelerate the aging of power transformers. Second, the accelerated aging transformer oil is taken as the research object, and the power frequency, DC, lightning, and gas chromatography are measured and analyzed. Finally, a transformer oil aging evaluation model is established, which takes into account four factors: carbon and oxygen gas factors in transformers, life loss factors calculated by hotspot temperature, hydrocarbon gas factors dissolved in transformer oil, and oil quality factors, and conducts aging evaluation. The conclusion shows that the T parameter proposed in this paper can effectively evaluate the quality of transformer oil. When T is less than or equal to 0.6, there is no aging of the oil. When T is greater than 0.6 and less than 1, the transformer oil has been aging, but it is not manifested. Those are parameters whose chromatography and breakdown voltage are not far beyond the IEEE standard. When T = 1, the aging of oil with significant changes in gas content and breakdown voltage can be observed. When T is greater than 1, the oil has undergone serious aging. [ABSTRACT FROM AUTHOR]

This paper aimed to research the function and in-depth mechanism of GPR37 in lung adenocarcinoma (LUAD). Herein, based on TCGA and Oncomine databases, we revealed that GPR37 was expressed at high levels in LUAD, and upregulation of GPR37 was related to the poor outcomes. Furthermore, biological function experiments in vitro were utilized to assess whether GPR37 impacts malignant phenotype of LUAD cells. Gain- or loss-of-function assays indicated that the upregulation of GPR37 contributed to improving the proliferation, migration, and invasion of LUAD cells in vitro, while knockdown of GPR37 can inhibit the malignant biological behaviors. Then, we found that depletion of GPR37 resulted in a decrease in the expression of TGF-β1 as well as the extents of Smad2 and Smad3 phosphorylation, while overexpression of GPR37 presented opposite outcomes. Altogether, our findings indicated that GPR37 is a potential oncogene of LUAD, and its promoting effects on the malignant progression of LUAD may be realized via TGF-β/Smad pathway.

Converter transformer is the key equipment in UHVDC transmission. If a local overheating fault occurs, it will inevitably form a local hot spot on the core, winding or other structural parts. Among these faults, multipoint grounding and interlaminar short circuit faults account for 30–50% of core accidents. The continuous overheating of 150–250 °C will cause ablation on the silicon steel sheet, which will destroy the insulation material and reduce the insulation performance. In severe cases, it will cause thermal expansion, resulting in local deformation or displacement of the core. Considering the scale of size and temperature parameters, the scale model of converter transformer is established based on the principle of constant magnetic flux density. By using the homogenization theory, the scaled model under multipoint grounding and interlaminar short circuit fault is simulated by electromagnetic heat. First, the single-phase four-column model of the core is established according to the scaled principle, and the core is refined. Secondly, taking the refined model as the research object, the magnetic thermal coupling simulation and analysis are carried out under multi-point grounding and interlaminar short circuit fault, and the magnetic density, eddy current loss and temperature distribution on each lamination are obtained. Finally, the correctness of the simulation is verified by the one-dimensional eddy current loss analytical equation, which provides a reference for the local overheating problem of converter transformers. [ABSTRACT FROM AUTHOR]