检索结果-南通市图书馆

老挝厚叶沉香中1个新的2-(2-苯乙基)色酮和木脂素杂合物及其抑制一氧化氮作用

在线全文

学校读者我要写书评

暂无评论

中草药 2024年第15期55卷 5011-5017页

作者：李薇王昊董文化曾军袁靖喆王雅丽吴妃梅文莉戴好富中国热带农业科学院热带生物技术研究所沉香国际联合研究中心/海南省黎药资源天然产物研究与利用重点实验室/海南热带农业资源研究院海南省热带农业生物资源保护与利用重点实验室海南海口571101

目的研究老挝厚叶沉香Aquilaria crassna植物所产沉香的化学成分及其抑制一氧化氮作用。方法采用硅胶、Sephadex LH-20凝胶、高效液相色谱等多种色谱技术分离纯化得到单体化合物;通过质谱、核磁共振等谱学方法并结合理化性质鉴定其结构... 详细信息

目的研究老挝厚叶沉香Aquilaria crassna植物所产沉香的化学成分及其抑制一氧化氮作用。方法采用硅胶、Sephadex LH-20凝胶、高效液相色谱等多种色谱技术分离纯化得到单体化合物;通过质谱、核磁共振等谱学方法并结合理化性质鉴定其结构;采用脂多糖诱导的小鼠单核巨噬细胞RAW264.7模型测试化合物抑制一氧化氮产生的抗炎活性。结果从老挝沉香的乙醇提取物中分离鉴定3个化合物,分别是厚叶沉香醇(1)、8-氯-6-羟基-2-(2-苯乙基)色酮(2)和8-氯-6-羟基-2-[2-(4-甲氧基苯)乙基]色酮(3)。化合物1对脂多糖诱导的小鼠单核巨噬细胞RAW264.7产生一氧化氮具有抑制作用,其半数抑制浓度值为(47.53±2.14)μmol/L。结论化合物1为新化合物,命名为厚叶沉香醇,是从沉香中首个发现的由2-(2-苯乙基)色酮和木脂素形成的杂合物,且对脂多糖诱导的RAW264.7细胞株产生一氧化氮呈现抑制活性。

关键词：沉香厚叶沉香厚叶沉香醇 2-(2-苯乙基)色酮杂聚体抑制一氧化氮产生活性

Chemical constituents from agarwood of Aquilaria filaria

在线全文

学校读者我要写书评

暂无评论

Journal of Chinese Pharmaceutical Sciences 2021年第6期30卷 505-517页

作者： Chengneng Mi Wenli Mei jingzhe yuan Wenxing Long HaofU Dai Hainan Engineering Research Center of Agarwood Institute of Tropical Bioscience and BiotechnologyChinese Academy of Tropical Agricultural SciencesHaikou 571101China Hainan Key Laboratory for Research and Development of Natural Products from Li Folk Medicine Haikou 571101China Institute of Tropical Agriculture and Forestry Hainan UniversityHaikou 570228China

Investigations on the chemical constituents from the ethanol extract of the agarwood originating from Aquilaria filaria led to the isolation of 26 compounds by column chromatography,including silica gel,Sephadex LH-20,and semi-preparative high-performance liquid *** structures were determined to beβ-sitostenone(1),24α-ethyl-cholestan-3α-ol(2),ergosta-4,6,8(14),22-tetraene-3-one(3),gypsogenin(4),hederagenin(5),17αH-trisnorhopanone(6),lupeol(7),friedelin(8),(-)-episyringaresinol(9),(-)-syringaresinol(10),5-hydroxy-7,4′-dimethoxyflavone(11),5,4’-dihydroxy-7,3′-dimethoxyflavone(12),2′-hydroxy-4,3′,6′,4′′-tetramethoxy-p-terphenyl(13),scopularide A(14),4-(4-hydroxyphenyl)butan-2-one(15),zingerone(16),coniferaldehyde(17),scopoletin(18),acetovanillon(19),isovanillin(20),vanillin(21),p-hydroxybenzaldehyde(22),p-hydroxybenzoic acid(23),protocatechuic acid(24),vanillic acid(25)and 4,5-dihydroxy-3-methoxybenzoic acid(26)by using spectroscopic *** compounds were isolated from agarwood of *** for the first time,and this was also the first report about the isolation of compounds 2,4,6,7,9,10,13-15,17-20,22,24 and 26 from agarwood and Aquilaria plants.

关键词： Agarwood of Aquilaria filaria Chemical constituents Triterpene Steroid

在线全文

学校读者我要写书评

暂无评论

二臂超支化聚羧酸减水剂的合成表征及性能

高分子材料科学与工程 2022年第2期38卷 46-55页

作者：姚方袁靖喆孙妍潘莉莎徐鼐庞素娟海南大学化学工程与技术学院海南海口570228

以氯化亚砜和甲氧基聚乙二醇(MPEG)为原料合成氯代甲氧基聚乙二醇(Cl-MPEG),对乙醇胺表面的氨基进行聚乙二醇(PEG)长链接枝,通过丙烯酰氯进一步引入双键合成二臂超支化聚氧乙烯醚大单体(TAHBPE)。将TAHBPE与丙烯酸小单体采用水溶液自由... 详细信息

以氯化亚砜和甲氧基聚乙二醇(MPEG)为原料合成氯代甲氧基聚乙二醇(Cl-MPEG),对乙醇胺表面的氨基进行聚乙二醇(PEG)长链接枝,通过丙烯酰氯进一步引入双键合成二臂超支化聚氧乙烯醚大单体(TAHBPE)。将TAHBPE与丙烯酸小单体采用水溶液自由基共聚法合成二臂侧链超支化型聚羧酸减水剂(TAHB-PCEs)。采用红外光谱、核磁共振、质谱、凝胶渗透色谱对合成过程的中间和最终产物进行了结构表征。结果表明,成功合成了Cl-MPEG,TAHBPE和TAHB-PCEs。净浆流动度和流变性测试结果表明,TAHB-PCEs的净浆流动度达到298.5 mm,屈服应力和黏度均小于传统梳型聚羧酸减水剂。通过表面张力、接触角对TAHB-PCEs的分散作用机理进行了探讨,保持聚羧酸减水剂的羧酸根密度不变、缩短侧链长度、增大侧链密度可降低其表面张力和表面能,有利于其在水泥表面的润湿,达到更好的减水分散性能。

关键词：聚羧酸减水剂二臂侧链超支化

Robustness of the octupole collectivity in 144Ba within the cranking covariant density functional theory in 3D lattice

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第8期35卷 124-131页

作者： Ze‑Kai Li yuan‑yuan Wang Mathematics and Physics Department North China Electric Power UniversityBeijing 102206China Hebei Key Laboratory of Physics and Energy Technology North China Electric Power UniversityBaoding 071000China

The octupole deformation and collectivity in octupole double-magic nucleus 144Ba are investigated using the Cranking covariant density functional theory in a three-dimensional lattice *** reduced B(E3)transition probability is implemented for the first time in semiclassical approximation based on the microscopically calculated electric octupole *** available data,including the I-ωrelation and electric transitional probabilities B(E2)and B(E3)are well ***,it is shown that the ground state of 144Ba exhibits axial octupole and quadrupole deformations that persist up to high spins(I≈24h).

关键词： Octupole collectivity Cranking covariant density functional theory Rotational spectrum Electric transitional probabilities

Global adaptive output-feedback tracking with prescribed performance for uncertain nonlinear systems

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2024年第5期67卷 150-164页

作者： yuan WANG Yungang LIU School of Control Science and Engineering Shandong University

At present, one typical control strategy for guaranteeing transient and steady-state performance is funnel control and prescribed performance control. The strategy features completely discarding the system nonlinearities, even if they are completely known and available. Such an intrinsic feature requires the controller to produce a larger control effect to eliminate the negative impact caused by the high nonlinearities, leading to a conservative controller. In this paper, we fully take advantage of known information on nonlinearities in control design, instead of completely discarding it as done in funnel control. Particularly, we leverage adaptive techniques(i.e., high-gain dynamic compensation) to deal with unknown system nonlinearities. Meanwhile, we integrate the tools of output feedback, tracking control, and the performance *** such, an adaptive output-feedback scheme is developed for global tracking with spatiotemporal performance specifications: arbitrarily given tracking accuracy and accuracy-ensured time. A simulation example supports the developed approach.

关键词： uncertain nonlinear systems output feedback prescribed performance unknown control direction dynamic high gain global tracking

Collective Molecular Machines: Multidimensionality and Reconfigurability

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Nano-Micro Letters 2024年第8期16卷 309-340页

作者： Bin Wang yuan Lu Department of Chemical Engineering Tsinghua UniversityBeijing 100084People’s Republic of China Key Laboratory of Industrial Biocatalysis Ministry of EducationTsinghua UniversityBeijing 100084People’s Republic of China

Molecular machines are key to cellular activity where they are involved in converting chemical and light energy into efficient mechanical *** the last 60 years,designing molecular structures capable of generating unidirectional mechanical motion at the nanoscale has been the topic of intense *** progress has been made,attributed to advances in various fields such as supramolecular chemistry,biology and nanotechnology,and ***,individual molecular machines are only capable of producing nanometer work and generally have only a single *** order to address these problems,collective behaviors realized by integrating several or more of these individual mechanical units in space and time have become a new *** this review,we comprehensively discuss recent developments in the collective behaviors of molecular *** particular,collective behavior is divided into two *** is the appropriate integration of molecular machines to efficiently amplify molecular motions and deformations to construct novel functional *** other is the construction of swarming modes at the supramolecular level to perform nanoscale or microscale *** discuss design strategies for both modes and focus on the modulation of features and ***,in order to address existing challenges,the idea of transferring experience gained in the field of micro/nano robotics is presented,offering prospects for future developments in the collective behavior of molecular machines.

关键词： Molecular machines Collective control Collective behaviors DNA Biomolecular motors

MAUN:Memory-Augmented Deep Unfolding Network for Hyperspectral Image Reconstruction

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2024年第5期11卷 1139-1150页

作者： Qian Hu Jiayi Ma yuan Gao Junjun Jiang Yixuan yuan Electronic Information School Wuhan UniversityWuhan 430072China School of Computer Science and Technology Harbin Institute of TechnologyHarbin 150001China Department of Electronic Engineering Chinese University of Hong KongHong Kong 999077China

Spectral compressive imaging has emerged as a powerful technique to collect the 3D spectral information as 2D *** algorithm for restoring the original 3D hyperspectral images(HSIs)from compressive measurements is pivotal in the imaging *** approaches painstakingly designed networks to directly map compressive measurements to HSIs,resulting in the lack of interpretability without exploiting the imaging *** some recent works have introduced the deep unfolding framework for explainable reconstruction,the performance of these methods is still limited by the weak information transmission between iterative *** this paper,we propose a Memory-Augmented deep Unfolding Network,termed MAUN,for explainable and accurate HSI ***,MAUN implements a novel CNN scheme to facilitate a better extrapolation step of the fast iterative shrinkage-thresholding algorithm,introducing an extra momentum incorporation step for each iteration to alleviate the information ***,to exploit the high correlation of intermediate images from neighboring iterations,we customize a cross-stage transformer(CSFormer)as the deep denoiser to simultaneously capture self-similarity from both in-stage and cross-stage features,which is the first attempt to model the long-distance dependencies between iteration *** experiments demonstrate that the proposed MAUN is superior to other state-of-the-art methods both visually and *** code is publicly available at https://***/HuQ1an/MAUN.

关键词： Deep folding iteration

Gradient microstructure and superior strength-ductility synergy of AZ61 magnesium alloy bars processed by radial forging with different deformation temperatures

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2024年第3期170卷 65-77页

作者： Jingfeng Zou Lifeng Ma Yanchun Zhu Ling Qin yuan yuan School of Mechanical Engineering Taiyuan University of Science and TechnologyTaiyuan 030024China Heavy Machinery Engineering Research Center of the Ministry Education Taiyuan University of Science and TechnologyTaiyuan 030024China Department of Engineering University of HullCottingham RdHull HU67RXUK National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing 400044China

Gradient microstructure modification is a cost-efficient strategy for high strength without compromising ductility,which is urgently needed in the fundamental science of engineering *** this study,heterogeneous structures of AZ61 alloy bars with anisotropic gradients(with different grain size distributions from the surface to the center)were observed to exhibit strong strength-ductility synergies under different deformation tem *** results reveal that the grain refinement process under mediumlow temperature deformation conditions(≤350℃)consists of four transition stages along the radial direction,i.e.,twin activations and deformation band formations,dislocation cells and pile-ups,ultrafine sub-grains,and randomly orientated quasi-micron *** deformation temperatures have a great influence on twin activations and deformation band formations,and the high temperature can easily provoke the initiation of non-basal *** deformation bands were determined as a primary nucleation site due to their highly unstable dislocation hindrance *** in combination with the Radial forging(RF)deformation process,the differences of dynamic precipitates can be attributed to microstructural difference and solubility limit of Al at different tem *** summarizing the tensile test results,the sample forged at 350℃exhibited the best strength-ductility synergy,exhibiting the highest elongation(EL)of 23.2%with a 251 MPa yield strength(YS)and 394 MPa ultimate tensile strength(UTS)in center region,and combined with the highest strength value of 256 MPa YS and 420 MPa UTS in the center region,while the EL was slightly degraded to 19.8%.

关键词： Gradient microstructure Radial forging Strength-ductility synergy Magnesium alloy Strengthening mechanism

Pyrolysis Empirical Modeling of Polyester Glass Fiber Reinforced Plastics Using Sestak-Berggren Model Method

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Thermal Science 2024年第2期33卷 725-738页

作者： NAN Wei JI Wenhui yuan Yanping yuan Zhongyuan SUN Yong School of Mechanical Engineering Southwest Jiaotong UniversityChengdu610031China CRRC Changchun Railway Vehicles Co. LtdChangchun130062China

Polyester Glass Fiber Reinforced Plastic(Polyester GFRP),a thermosetting plastic comprised of glass fiber and polyester polymer compounds,is extensively utilized in high-speed *** its pyrolysis mechanism is crucial as it significantly influences the combustion characteristics and fire safety ***,kinetic research on polyester GFRP primarily focuses on employing the Coats-Redfern method to derive a theoretical kinetic ***,the pyrolysis process of polyester GFRP is complex and the aforementioned theoretical model fails to accurately describe the pyrolysis ***,this study seeks to utilize the Sestak and Berggren(SB) model as a methodological approach to reveal the complex reaction mechanism during the pyrolysis *** on thermogravimetric analysis,the entire pyrolysis process of polyester GFRP is divided into two primary ***,model-free methods are employed to ascertain the activation energy and pre-exponential *** results show that the fitted empirical models of the two main pyrolysis stages are f(α)=(1-α)^(1.47)[-ln(1-α)]^(1.50) and f(α)=(1-α)^(1.77)[-ln(1-α)]^(1.72),*** predicted results are in good agreement with experimental data under different heating rates,which indicates that the empirical model can sufficiently describe the pyrolysis process of polyester GFRP.

关键词： polyester GFRP model-fitting methods empirical models pyrolysis