桑叶黄酮类化合物的研究进展

黄酮类化合物是桑叶中重要的活性成分,具有抗氧化、降血糖、抗癌等药理学作用。对近年来桑叶黄酮类化合物的提取方法、分离纯化方法、含量检测及药理学作用等进行了综述。     

仙人掌黄酮类化合物的研究进展

对仙人掌黄酮类化合物的结构与分类、提取方法、分离纯化、药理作用等方面的研究进展进行了综述,指出仙人掌黄酮类化合物研究存在的问题,为进一步开发利用仙人掌资源提供依据。     

黄酮类化合物提取和纯化工艺研究进展

黄酮类化合物是一类活性物质,具有特殊的保健及治疗功能.本文分析了黄酮的结构特征,介绍了黄酮的提取工艺和分离纯化,并对各工艺利弊进行了分析.     

杜仲叶黄酮类化合物的提取纯化及功能活性分析

目前杜仲叶应用主要为动物饲料,导致了资源的极大浪费.以杜仲叶黄酮类化合物为主要活性成分进行资料汇总,分别探讨了杜仲叶黄酮类化合物的提取工艺、分离纯化方法、功能活性研究等内容,希望对杜仲叶的功能食品开发和深度资源利用提供一定的理论依据.     

双水相萃取法分离纯化黄酮类化合物的研究进展

综述双水相体系的组成、特点和双水相萃取法分离纯化黄酮类化合物的研究进展。双水相萃取是一项利用不复杂的设备,并在温和条件下进行简单的操作就可获得较高收率和有效成分的新型分离技术,该技术在黄酮类化合物的分离分析中取得了较好的效果,有望成为一种新型的黄酮类化合物的分离纯化方法。     

中药石韦中黄酮类化合物的含量及抗氧化活性研究

目的:对中药石韦中黄酮类化合物进行分离纯化,并对分离纯化后的不同极性的黄酮类成分进行体外抗氧化活性研究。方法:利用超声法提取中药石韦中的黄酮类成分,用乙酸乙酯和正丁醇反复萃取后,将乙酸乙酯萃取液(S_1)用聚酰胺柱分离纯化,分别用体积分数30%、50%、75%乙醇溶液进行洗脱,蒸干后得到3个样品S_2、S_3、S_4(正丁醇萃取液得到的样品记为S_5)。对所得样品进行体外抗氧化活性分析。结果:黄酮类化合物含量:S_4S_1S_5S_3S_2;体外抗氧化活性:S_4S_5S_3S_2。结论:中药石韦中黄酮类化合物有较好的抗氧化活性。其中,75%乙醇洗脱的样品(S_4)黄酮类化合物含量最高,且抗氧化活性最好。说明中药石韦中的黄酮类化合物有较好的抗氧化活性。     

银杏双黄酮类化合物研究进展

我国有着丰富的银杏叶资源,而银杏叶中双黄酮类化合物具有多种生物活性,本文介绍了银杏叶中双黄酮类化合物的发现过程,综述了双黄酮类化合物的提取纯化方法,并详细介绍了双黄酮类化合物的各种生物活性,展望了双黄酮类化合物的应用前景。     

聚酰胺在黄酮类化合物分离纯化中的应用

聚酰胺是一类大分子主链重复单元中含有酰胺基团的高聚物的总称。黄酮类化合物是存在于自然界的、具有2-苯基色原酮结构的一类化合物。可利用聚酰胺氢键吸附的原理,对天然药物中黄酮类化合物进行分离纯化。在查阅近几年来国内相关文献的基础上,对聚酰胺在黄酮类化合物分离提纯中的应用进行综合叙述,旨在为聚酰胺在天然产物提取的应用提供思路。     

紫花苜蓿中黄酮类化合物分离及特殊显色反应研究

本研究旨在分离紫花苜蓿中的黄酮类化合物,并进行特殊显色反应相关研究。研究人员通过植物采集和样品制备,获得了紫花苜蓿的植物材料。研究人员采用萃取方法和分离富集方法,成功地从植物材料中提取出黄酮类化合物。其中,柱色谱技术和液液萃取是本研究中主要的分离富集手段。通过黄铜色素的纯化步骤,获得了高纯度的黄酮类化合物。在黄酮色素的紫外光谱分析中,实验过程中采用了先进的光谱技术,得到了详细的实验结果。通过实验结果的分析,确定了所得黄酮类化合物的结构和纯度,为后续研究奠定了坚实的基础。综合研究结果,本研究成功地实现了紫花苜蓿中黄酮类化合物的分离、富集和特殊显色反应的研究目标。所获得的高纯度黄酮类化合物为进一步的生物活性研究提供了有力的实验基础,为紫花苜蓿及相关植物资源的开发利用提供了重要的科学依据。     

大孔吸附树脂分离纯化黄酮类化合物的研究进展

黄酮类化合物是在植物中分布非常广泛的一类天然产物,具有多种生物活性。大孔吸附树脂纯化是一项不需复杂设备、操作条件温和的新型分离技术。综述了大孔吸附树脂分离纯化黄酮类化合物的研究进展。     

乙苯,苯乙烯的生产及合成乙苯,苯乙烯催化剂的研究进展

苯乙烯是重要的石油化工原料。本文介绍了国内外苯乙烯生产的发展概况，合成乙苯，苯乙烯所用的催化剂种类，并就苯乙烯生产及催化剂的发展趋势提出了自己的观点。     

Synthesis and characterization of homopolymers and copolymers of various acrylates and acrylonitrile

Various homopolymers and copolymers of methyl acrylate, ethyl acrylate, butyl acrylate, and acrylonitrile in different feed ratios were synthesized. These were characterized by IR, ¹³C-NMR, DSC, DTA, and TGA. Spectroscopic characterization helped in differentiating copolymers of different mol ratios. Thermal analysis revealed different degradation patterns for homopolymers and copolymers. The temperature and energy changes associated with various phase transitions were dependent on the chemical composition of homo- and copolymers, as expected. © 1993 John Wiley & Sons, Inc.     

生物质气化及生物质与煤共气化技术的研发与应用

总结了生物质原料的特点及生物质单独气化的缺点;介绍了国内外生物质气化技术及生物质与煤共气化技术的研发与应用现状;分析了在此领域国内外的发展趋势与前景;概括了开展生物质与煤共气化技术研发的意义。     

责任和责任心的涵义与结构

责任是人应主动承担的角色义务和对其因过失所造成后果应承担的责罚.有两层涵义:一是义务;二是后果.责任心是个体自觉做好分内事务和履行道德义务的心理倾向,是个性心理品质成分中自我特征维度上的重要内容.责任心具有两个方面的涵义:一是角色分内职责;二是角色道德义务.责任心是一种通过责任认知、责任个性和责任适应的动态形式表现出来的静态品质,责任心是责任心过程结构与责任心关系结构相互制约、相互影响的统一体.     

二甲基二烯丙基氯化铵和丙烯酰胺的合成及应用

用复合引发体系(过硫酸盐-偶氮类引发剂)和脂肪胺类氧化还原体系引发,在实验室获得了单体转化率≥98%,特性粘数高于13.6 dL/g的阳离子共聚物PDA,探讨了控制聚合物分子量的影响因素.     

Comparison of the Adhesion and Cohesion of Triblock and Random Copolymers of Styrene and Butadiene

A substantially greater detachment energy is required to strip a polyethylene tereph-thalate (Mylar) film from a styrene-butadiene-styrene (SBS) triblock copolymer compared to that for peeling from a random styrene-butadiene (SBR) copolymer. This is true even though the intrinsic interaction between the Mylar and each elastomer is expected to be similar because of their virtually identical chemical composition. It is proposed that this difference in peel strength (between the SBS and SBR) is a consequence of the much higher dissipative capacity of the former elastomer. Another manifestation of this is the higher cohesive tear strength of the SBS compared to the SBR. Extents of energy dissipation within each elastomer during detachment of the Mylar adherend are consistent with the hypothesis that the average maximum stress experience before detachment is some similar fraction of each elastomer's tensile strength.     

Kinetics and Mechanism of Oxidation of Mono- and Polyacetals

Abstract

Kinetics and mechanisms of oxidation of 6 acetals by molecular oxygen and ozone in liquid phase have been studied. Reaction with molecular oxygen (70°C, 15–16 hr) leads to the formation monoethers of the corresponding glycols with 68–90% selectivity. Salts of metals and complexes with crown-ethers have increased the reaction rate significally. Ozone have reacted with acetals with formation similar products. The mechanisms of intermediate stages have been proposed.     

钾盐资源及钾肥供需情况分析及预测

阐述了国内外钾盐资源及钾肥生产现状,对国内外钾盐的供需形势进行了分析及预测,从资源、原材料、国际市场三方面提出了解决我国钾盐短缺的措施。     

Electronic structures and reactivities of monometallic and bimetallic clusters of Au and Cu

The variation of the Au 4f binding energy of Au clusters with the cluster size has been established by measuring the binding energies of clusters whose size distributions were independently determined by HREM and STM. The binding energy increases significantly when the cluster size is less than 2 nm. Au-Cu bimetallic clusters of the composition Cu₃Au have been deposited for the first time on carbon substrates. The shifts in the core level binding energies of the bimetallic clusters show the effect of alloying in the case of large clusters, but show effects of both alloying and cluster size in the case of the small clusters. The interaction of CO with Cu₃Au clusters is stronger than with a bulk Cu metal. The interaction of CO with small Cu clusters also seems to be stronger than with bulk Cu or with large Cu clusters.     

Wetting properties of homopolymers and copolymers of pentafluorostyrene and methylacrylate and homopolymer blends

Polypentafluorostyrene (PPFS), polymethylacrylate (PMA), and poly(pentafluorostyrene-co-methylacrylate), poly(PFS-co-MA) were prepared and the wetting characteristics of polymer blends of PPFS and PMA were compared with that of poly(PFS-co-MA) via contact angle measurements. The critical surface tension of polypentafluorostyrene was found to be 22.6 dyne/cm, which is comparable to the value reported for polytrifluoroethylene (22 dyne/cm). The critical surface tension of poly(PFS-co-MA) is not linearly related to its composition. The polymer blends of PPFS and PMA exhibit significant surface enrichment of the fluoropolymer. The harmonic-mean method¹ was employed to determine surface tensions of these polymers and many known polymers. It is found that the method produces useful surface tension data provided the contact angle values are derived from testing liquids of dissimilar polarity.