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991.
Ge Ma Qianshu Wang Jun Ye Lifan He Longhai Guo Xiaoyu Li Teng Qiu Xinlin Tuo 《Molecules (Basel, Switzerland)》2022,27(21)
The comprehensive balance of the mechanical, interfacial, and environmental requirements of waterborne polyurethane (WPU) has proved challenging, but crucial in the specific application as the binder for high-performance polymer fiber composites. In this work, a multi-step chain extension (MCE) method was demonstrated using three kinds of small extenders and one kind of macro-chain extender (CE) for different chain extension steps. One dihydroxyl blocked small molecular urea (1,3-dimethylolurea, DMU) was applied as one of the CEs and, through the hybrid macrodiol/diamine systems of polyether, polyester, and polysiloxane, the WPU was developed by the step-by-step optimization on each chain extending reaction via the characterization on the H-bonding association, microphase separation, and mechanical properties. The best performance was achieved when the ratio of polyether/polyester was controlled at 6:4, while 2% of DMU and 1% of polysiloxane diamine was incorporated in the third and fourth chain extension steps, respectively. Under the condition, the WPU exhibited not only excellent tensile strength of 30 MPa, elongation of break of about 1300%, and hydrophobicity indicated by the water contact angle of 98°, but also effective interfacial adhesion to para-aramid fabrics. The peeling strength of the joint based on the polysiloxane incorporated WPU after four steps of chain extension was 430% higher than that prepared through only two steps of chain extension. Moreover, about 44% of the peeling strength was sustained after the joint had been boiling for 40 min in water, suggesting the potential application for high-performance fabric composites. 相似文献
992.
993.
为了实现在大气压下低触发电压的多通道放电,以阵列微孔阴极结构作为触发装置设计了一种新型纳秒脉冲开关。以激光打孔的双面环氧板为阵列微孔阴极,研究了开关工作系数、微孔阴极放电电流、微孔阴极孔数及微孔阴极孔径对开关触发电压、延迟和抖动时间的影响。实验结果表明:更多的阵列微孔、100 m的微孔孔径能够降低开关的触发电压,同时高开关工作系数、大触发电流、多阵列微孔能够减少开关的延迟和抖动时间。因此,为了获得更高性能的纳秒脉冲开关,除了对开关结构的进一步改善,这几个影响开关性能的因素是设计开关时应主要考虑的。 相似文献
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996.
The dual-interference fiber optical gyroscope (DIFOG) is a novel gyroscope that makes use of both birefringent axes in a polarization maintained fiber to generate two Sagnac interferometers. The Sagnac effect is doubled in the DIFOG, resulting in the same precision for a smaller fiber coil and shorter fiber, so it has some potential applications in miniaturized and low-cost situations. The mechanism of polarization nonreciprocity (PNR) in the DIFOG is investigated and the influence of PNR is analyzed theoretically. Simulation results based on the theoretical analysis indicate that PNR error causes the bias of interference signals and the output of the DIFOG to vary with the inherent nonreciprocal phase that arises from the optical configuration. The experiment verifies the theoretical and simulation results. 相似文献
997.
998.
Chemical fingerprint and simultaneous determination of alkaloids and flavonoids in aerial parts of genus Peganum indigenous to China based on HPLC‐UV: application of analysis on secondary metabolites accumulation
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Wei Liu Min Xuan Lei Zhang Xin Zhao Meng Shan Yan Li Liang Teng Zhengtao Wang Changhong Wang 《Biomedical chromatography : BMC》2014,28(12):1763-1773
The aerial parts of genus Peganum are officially used in traditional Chinese medicine. The paper aims to establish a high‐performance liquid chromatography (HPLC) method for fingerprint analysis and simultaneous determination of three alkaloids and two flavonoids in aerial parts of genus Peganum, and to analyze accumulative difference of secondary metabolites in inter‐species, individuals of plants, inter‐/intra‐population and from different growing seasons. HPLC analysis was performed on a C18 column with gradient elution using 0.1% trifloroacetic acid and acetonitrile as mobile phase and detected at 265 nm, by conventional methodology validation. For fingerprint analysis, the RSDs of relative retention time and relative peak area of the characteristic peaks were within 0.07–0.78 and 0.94–9.09%, respectively. For simultaneous determination of vasicine, harmaline, harmine, deacetylpeganetin and peganetin, all calibration curves showed good linearity (r > 0.9990) within the test range. The relative standard deviations of precision, repeatability and stability test did not exceed 2.37, 2.68 and 2.67%, respectively. The average recoveries for the five analytes were between 96.47 and 101.20%. HPLC fingerprints play a minor role in authenticating and differentiating the herbs of different species of genus Peganum. However, the secondary metabolites levels of alkaloids and flavonoids in aerial parts of genus Peganum rely on species‐, habitat‐, and growth season‐dependent accumulation. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
999.
Xiaoxu Teng Mingyu Tian Jinwen Zhang Lijun Tang Junna Xin 《Tetrahedron letters》2018,59(29):2804-2808
A new fluorescent probe (TCF-AC) that contains 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) skeleton has been developed. Probe TCF-AC exhibits highly selective and sensitive detection toward Pd0 in EtOH/H2O (1:1, v/v, PBS 20?mM, pH?=?7.4) solution with fluorescence “turn on” and colorimetric changes. The Pd0 detection by TCF-AC holds some advantages including good anti-interference ability, a relative large Stokes shift (>100?nm), and a low detection limit (7.05?×?10?7?M). Cell imaging studies demonstrate that TCF-AC is applicable to detect Pd0 in living HeLa cells. 相似文献
1000.
Simultaneous determination of sesquiterpene lactones isoalantolactone and alantolactone isomers in rat plasma by liquid chromatography with tandem mass spectrometry: Application to a pharmacokinetic study
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A selective, sensitive, and accurate LC–MS/MS method for the simultaneous determination of isoalantolactone and alantolactone in rat plasma has been developed using psoralen as the internal standard. LC–MS/MS analysis was carried out on a Triple Quadrupole mass spectrometer using positive ion ESI and the selected reaction monitoring mode. The assays were linear in the range of 7.5–750 ng/mL for isoalantolactone and 5.5–550 ng/mL for alantolactone. The average recoveries in plasma samples both were better than 85%. The intra‐ and inter‐day precision and accuracy values were found to be within the assay variability criteria limits according to the US FDA guidelines. The method was successfully applied to pharmacokinetic studies of the two structural isomers after an intravenous injection of Inula helenium formulation to rats. 相似文献