Two Novel Phenolic Compounds from the Rhizomes of Cyperus rotundus L.

Two novel compounds, 1α-methoxy-3β-hydroxy-4α-(3′,4′-dihydroxyphenyl)-1, 2,3,4-tetrahydronaphthalin (1) and 1α,3β-dihydroxy-4α-(3′,4′-dihydroxyphenyl)-1,2,3,4-tetrahydronaphthalin (2), were isolated along with six known compounds 3–8 from the rhizomes of Cyperus rotundus. This paper reports the isolation and full spectroscopic characterization of these new compounds by NMR, UV, IR and MS data

A Combined Electro-Thermal Breakdown Model for Oil-Impregnated Paper

The breakdown property of oil-impregnated paper is a key factor for converter transformer design and operation, but it is not well understood. In this paper, breakdown voltages of oil-impregnated paper were measured at different temperatures. The results showed that with the increase of temperature, electrical, electro-thermal and thermal breakdown occurred successively. An electro-thermal breakdown model was proposed based on the heat equilibrium and space charge transport, and negative differential mobility was introduced to the model. It was shown that carrier mobility determined whether it was electrical or thermal breakdown, and the model can effectively explain the temperature-dependent breakdown

Dramatically enhanced electrical breakdown strength in cellulose nanopaper

Electrical breakdown behaviors of nanopaper prepared from nanofibrillated cellulose (NFC) were investigated. Compared to conventional insulating paper made from micro softwood fibers, nanopaper has a dramatically enhanced breakdown strength. Breakdown field of nanopaper is 67.7 kV/mm, whereas that of conventional paper is only 20 kV/mm. Air voids in the surface of conventional paper are observed by scanning electron microscope (SEM). Further analyses using mercury intrusion show that pore diameter of conventional paper is around 1.7 μm, while that of nanopaper is below 3 nm. Specific pore size of nanopaper is determined to be approximately 2.8 nm by the gas adsorption technique. In addition, theoretical breakdown strengths of nanopaper and conventional paper are also calculated to evaluate the effect of pore size. It turns out that theoretical values agree well with experimental data, indicating that the improved strength in nanopaper is mainly attributed to the decreased pore size. Due to its outstanding breakdown strength, this study indicates the suitability of nanopaper for electrical insulation in ultra-high voltage convert transformers and other electrical devices

Electrical Trees and Their Growth in Silicone Rubber at Various Voltage Frequencies

The insulation property at high voltage frequencies has become a tough challenge with the rapid development of high-voltage and high-frequency power electronics. In this paper, the electrical treeing behavior of silicone rubber (SIR) is examined and determined at various voltage frequencies, ranging from 50 Hz to 130 kHz. The results show that the initiation voltage of electrical trees decreased by 27.9% monotonically, and they became denser when the voltage frequency increased. A bubble-shaped deterioration phenomenon was observed when the voltage frequency exceeded 100 kHz. We analyze the typical treeing growth pattern at 50 Hz (including pine-like treeing growth and bush-like treeing growth) and the bubble-growing pattern at 130 kHz. Bubbles grew exponentially within several seconds. Moreover, bubble cavities were detected in electrical tree channels at 50 Hz. Combined with the bubble-growing characteristics at 130 kHz, a potential growing model for electrical trees and bubbles in SIR is proposed to explain the growing patterns at various voltage frequencies

Enhancing Insulating Performances of Presspaper by Introduction of Nanofibrillated Cellulose

This study explores the possibility of enhancing both mechanical and breakdown properties of insulating presspaper by the introduction of an organic nano additive. Four different concentrations of nanofibrillated cellulose (NFC) were taken into account: 0.5 wt %, 2.5 wt %, 5 wt %, and 10 wt %. Presspaper containing no NFC was also prepared as a reference. Obtained samples were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Mechanical properties and breakdown behaviors were measured. Results show that the addition of 10 wt % NFC to softwood fibers can achieve the best performance. Tensile strength of reference presspaper is 109 MPa, whereas that of presspaper modified by 10 wt % NFC is 136 MPa, resulting in a 25% increase. The improved tensile strength can be attributed to the increased density and inter fiber bond strength. More importantly, presspaper reinforced by 10 wt % NFC can also achieve enhanced AC and DC breakdown strengths, which are 19% and 21% higher than those of the reference presspaper. It is concluded that NFC is likely to be a promising nano additive for cellulose insulation

Predicting the Dielectric Properties of Nanocellulose-Modified Presspaper Based on the Multivariate Analysis Method

Nanocellulose-modified presspaper is a promising solution to achieve cellulose insulation with better performance, reducing the risk of electrical insulation failures of a converter transformer. Predicting the dielectric properties will help to further design and improvement of presspaper. In this paper, a multivariable method was adopted to determine the effect of softwood fiber on the macroscopic performance of presspaper. Based on the parameters selected using the optimum subset method, a multiple linear regression was built to model the relationship between the fiber properties and insulating performance of presspaper. The results show that the fiber width and crystallinity had an obvious influence on the mechanical properties of presspaper, and fiber length, fines, lignin, and nanocellulose had a significant impact on the breakdown properties. The proposed models exhibit a prediction accuracy of higher than 90% when verified with the experimental results. Finally, the effect of nanocellulose on the breakdown strength of presspaper was taken into account and new models were derived

The anti-hepatic fibrosis effects of chlorogenic acid extracted from Artemisia Capillaris Herba on CCl4-induced mice via regulating TGF-β1/smad3 pathway

Introduction: Artemisia Capillaris Herba, a famous traditional Chinese medicine, is effective for the treatment of hepatic fibrosis(HF) in clinical applications. Research has confirmed that chlorogenic acid (CA), an organic acid compound was extracted from Artemisia Capillaris Herba, could reduce the hepatocyte injury induced by HF, however, its mechanism of anti-HF is still unclear, and we investigated whether CA could help treating HF mice. Methods: In this study, we evaluated the therapeutic effect of CA on HF mice induced by CCl4, which was extracted from Artemisia Capillaris Herba and identified by 1H NMR and 13C NMR spectroscopy. Seventy two NIH mice were divided into following groups: normal group, model group, low, medium and high dose of CA groups (7.5, 15, 30 mg/kg) and colchicine (Colc)-positive control group (0.2 mg/kg). All mice were injected 40% CCl4 for 8 weeks with a 24 h interval except normal mice. Each drug group and Colc group were given intragastric administration for 40 days while modeling. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), collage IV (Col-IV), hyaluronic acid (HA), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), procollagen typeⅢ (PC-Ⅲ), malondialdehyde (MDA) and laminin (LN) levels were detected by ELISA, samd3 and TGF-β1 were examined by immunohistochemistry and western blotting and the liver and kidney tissues were observed by HE. Results: At the end of administrations, the body weight of mice was decreased and the levels of ALT, AST, Col-IV, HA, IL-6, TNF-α, LN, PC-III, and MDA were increased in the HF modle mice compared with that of normal mice. Compared with the HF mice only, treatment with CA significantly decreased the levels of ALT, AST, Col-IV, HA, IL-6, TNF-α, LN, PC-III, and MDA. The HE staining results showed that the hepatic and nephritic injury were significantly alleviated after CA treatment. And the smad3 and TGF-β1 expression were inhibited in the CA-treated mice in comparison with the model mice. Conclusion: Conclusively, CA treatment could attenuate HF through the regulation of TGF-β1/smad3 pathway, suggesting that CA may be an effective component of Artemisia Capillaris Herba in the treatment of HF