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521.
Four new pregnane steroids, aglaiasterols A–D ( 1 – 4 ), have been isolated from the EtOH extract of stems of Aglaia abbreviata. They were identified as (3α,5α,17Z)‐3‐hydroxypregn‐17‐en‐16‐one ( 1 ), (3β,5α,17E)‐3‐hydroxypregn‐17‐en‐16‐one ( 2 ), (3β,5α,17Z)‐3‐hydroxypregn‐17‐en‐16‐one ( 3 ), and (3α,5α,20S*)‐3‐hydroxy‐16‐oxopregnan‐20‐yl acetate ( 4 ) on the basis of spectroscopic methods, including 1D‐ and 2D‐NMR techniques. Compounds 1 – 4 were evaluated for their cytotoxic activities against K562 (human leukemia), MCF‐7 (human breast cancer), and KB (human oral epithelium cancer) cells, and drug‐resistant cells of K562/A02, MCF‐7/ADM, and KB/VCR. These isolates showed weak to moderate inhibitory effects on the growth of the tested cell lines. 相似文献
522.
We present high-performance enhancement-mode AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs) by a fluorinated gate dielectric technique. A nanolaminate of an Al2O3/LaxAl1-xO3/Al2O3 stack (x≈0.33) grown by atomic layer deposition is employed to avoid fluorine ions implantation into the scaled barrier layer. Fabricated enhancement-mode MOS-HEMTs exhibit an excellent performance as compared to those with the conventional dielectric-last technique, delivering a large maximum drain current of 916 mA/mm and simultaneously a high peak transconductance of 342 mS/mm. The balanced DC characteristics indicate that advanced gate stack dielectrics combined with buffered fluorine ions implantation have a great potential for high speed GaN E/D-mode integrated circuit applications. 相似文献
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525.
Yuxiong Wang Guang Hong Yaoyu Zhang Prof. Yue Liu Dr. Wanglai Cen Prof. Lianzhou Wang Prof. Zhongbiao Wu 《Angewandte Chemie (International ed. in English)》2023,62(42):e202310525
C−H dissociation and C−C coupling are two key steps in converting CH4 into multi-carbon compounds. Here we report a synergy of Au and Ag to greatly promote C2H6 formation over Au1Ag single-atom alloy nanoparticles (Au1Ag NPs)-modified ZnO catalyst via photocatalytic oxidative coupling of methane (POCM) with O2 and H2O. Atomically dispersed Au in Au1Ag NPs effectively promotes the dissociation of O2 and H2O into *OOH, promoting C−H activation of CH4 on the photogenerated O− to form *CH3. Electron-deficient Au single atoms, as hopping ladders, also facilitate the migration of electron donor *CH3 from ZnO to Au1Ag NPs. Finally, *CH3 coupling can readily occur on Ag atoms of Au1Ag NPs. An excellent C2H6 yield of 14.0 mmol g−1 h−1 with a selectivity of 79 % and an apparent quantum yield of 14.6 % at 350 nm is obtained via POCM with O2 and H2O, which is at least two times that of the photocatalytic system. The bimetallic synergistic strategy offers guidance for future catalyst design for POCM with O2 and H2O. 相似文献
526.
Cen Li Lunjing Yan Meijun Wang Jiao Kong Weiren Bao Liping Chang 《Chemical record (New York, N.Y.)》2023,23(2):e202200216
It is significant for saving energy to manufacture superb-property batteries. Carbon is one of the most competitive anode materials in batteries, but it is hard for commercial graphite anodes to meet the increasingly higher energy-storage requirements. Moreover, the price of other better-performing carbon materials (such as graphene) is much higher than graphite, which is not conducive to massive production. Pitch, the cheap by-product in the petroleum and coal industries, has high carbon content and yield, making it possible for commercialization. Developing pitch-based anodes can not only lower raw material costs but also realize the pitch′s high value-added utilization. We comprehensively reviewed the latest synthesis strategies of pitch-derived materials and then introduced their application and research progress in lithium, sodium, and potassium ion batteries (LIBs, SIBs, and PIBs). Finally, we summarize and suggest the pitch′s development trend for anodes and in other fields. 相似文献
527.
Hongping Wei Cen Qi Xiaomin Xu Zhiping Zhang Yafeng Zhou Zongqiang Cui Xian-En Zhang Chengan Zhang 《Chromatographia》2008,67(5-6):491-494
Nucleic acid samples with high concentrations of salt could be stacked and well separated during capillary zone electrophoresis
(CZE) by adding glycerol into the samples and using a Tris-Borate-EDTA (TBE) buffer (pH 8.3) as the separation medium. The
so-called glycerol-salt mediated stacking was found applicable to different types of nucleic acids. Three nucleic acids: a
16s rRNA (1,542 nt), a double stranded DNA (1.6 k bp), and a single stranded DNA (30 nt), were tested as demos in the experiments.
When the sample matrix contained 50 mM KCl and 50% (w/v) glycerol, the 16s rRNA sample could be stacked as high as 30 times compared with the sample without KCl. All the nucleic
acids could be stacked effectively when high concentrations of glycerol (>50%) and salt (more than 50 mM) were present in
the sample matrix, while the dsDNA could be stacked with high concentrations of glycerol (>50%) alone.
Cen Qi and Hongping Wei contributed equally to this work. 相似文献
528.
Cen Yu Xiang Zhouyang Han Tingting Long Yu Song Tao 《Cellulose (London, England)》2022,29(13):7193-7209
Cellulose - In recent years, a new strategy of using citric acid (CA) to produce carboxylic cellulose nanocrystals (CNCs) has received attractive interest. However, mainly due to the weak acidity... 相似文献
529.
合成气经费托合成(Fischer-Tropsch synthesis,FTs)转化为燃料和高附加值化学品是解决煤炭等资源清洁利用问题的重要途径,是现代煤化工的重要组成部分,对于降低石油进口依赖度,保证国家能源战略安全具有重要意义。钴基催化剂因活性高、链增长活性强、CO2选择性低、寿命长等而成为目前研究最为广泛的FTs催化剂之一。如何通过调控表界面性质来打破还原度和分散度的依赖关系,提高催化剂的反应活性以及一定碳链范围内的产物选择性依然是高效钴基FTs催化剂开发面临的重要挑战。本文分别从结构敏感性(尺寸和晶面效应)、金属-载体间相互作用和限域效应三个方面阐述钴基FTs催化剂表界面性质调控策略的最新研究进展,以期为钴基FTs催化剂微观结构设计及反应性能调控提供理论依据。 相似文献
530.
All-optical high-speed binary data pattern recognition is one of the key technologies in network security applications.A serial pattern recognition scheme is presented,which can detect and locate a spe... 相似文献