茶多酚的加速溶剂萃取与分析

以毛尖茶叶为原料,用加速溶剂萃取法提取茶多酚粗品用单因素试验研究和正交试验考察乙醇体积分数、温度和循环次数对萃取率的影响。用二极管阵列高效液相色谱(DAD-HPLC)对照测定加速溶剂萃取的茶多酚粗品、微波辅助提取的茶多酚粗品和商品茶多酚。结果表明:茶多酚粗品的制备最佳条件为萃取温度160℃、乙醇体积分数60%、循环萃取2次。高温加速溶剂萃取法对茶多酚的粗提率较高,但其中儿茶素的总量却显著下降降低提取温度,则茶多酚中的主要功能成分儿茶素的含量显著高于微波辅助提取法。     

新疆蓝莓中花青素的超声-微波提取及抗氧化活性研究

优选蓝莓中花青素的超声-微波提取工艺,并研究其抗氧化活性。以儿茶素为标准品,选取乙醇浓度、料液比、微波功率、提取时间等考察因素,以花青素提取率为指标,在单因素试验的基础上,通过正交试验筛选出最佳的提取工艺条件。以VC为对照,通过清除羟自由基、DPPH·自由基和超氧阴离子自由基等实验来评价蓝莓中花青素体外抗氧化能力。乙醇浓度50%,液料比1∶60,超声功率50W,微波功率100W,提取时间180s时蓝莓中花青素的提取率最高,其含量达9.93%。蓝莓中花青素对羟自由基,DPPH·和超氧阴离子自由基都有一定清除能力。且在实验所选浓度范围内,抗氧化能力随浓度的增加而增强。     

不同加工形式茶叶茶多酚含量及抗氧化活性比较研究

目的:比较不同加工形式茶叶中茶多酚含量及其抗氧化活性,为不同需求人群提供选择依据。方法:茶叶粉碎后用95%乙醇超声提取,以没食子酸作为对照品,采用福林酚比色法在波长765 nm处测定各种茶叶中茶多酚的含量。抗氧化活性通过紫外分光光度法测定茶叶提取物对Fe3+的还原能力进行评价。结果:不同加工形式茶叶中茶多酚含量及抗氧化活性差异较大,其中绿茶茶多酚含量最高,其抗氧化活性也最好。结论:茶叶中多酚含量与茶叶发酵程度密切相关,发酵程度越大,茶多酚含量越低;茶叶提取物的抗氧化活性与茶多酚含量呈现良好的量效关系,说明茶叶的抗氧化能力主要与其中的茶多酚含量有关。     

马齿苋多糖提取优化及抗氧化活性研究

目的 优化微波辅助水提醇沉法提取马齿苋多糖的条件,并探讨其抗氧化活性.方法 采用微波辅助水提醇沉法,以单因素试验为基础,应用响应面优化提取马齿苋多糖工艺,测定其在体外对DPPH自由基(DPPH·)、羟自由基(·OH)和超氧自由基(O^-₂·)的清除率及对果蝇体内SOD活力和MDA含量的影响.结果 马齿苋多糖的最佳提取条件为粉碎度60目、液料比V(mL)∶m(g)=32∶1、微波时间12 min,在此条件下提取率为6.31%.马齿苋多糖具有体外清除DPPH自由基、羟自由基和超氧自由基的活性,还可提高果蝇体内SOD活力,降低果蝇体内MDA含量.结论 响应面优化工艺合理可行,提取的马齿苋多糖具有一定的综合抗氧化活性.     

超临界CO_2萃取茶叶籽油及其分子蒸馏馏出物抗氧化成分分析

以茶叶籽为原料,采用超临界CO2萃取得到茶叶籽油,通过分子蒸馏富集提取茶叶籽油中抗氧化成分,并采用UHPLC-TOF-MS分析其组成。结果表明,CO2流速对萃取速率影响较大,采用超临界CO2梯度萃取的模式,不同萃取阶段得到的茶叶籽油的酸价存在一定规律,在萃取初期,茶叶籽油的酸价较高,随着萃取过程的进行,酸价逐渐降低,说明游离脂肪酸更容易溶解在超临界CO2中。茶叶籽油分子蒸馏馏出物中主要的抗氧化成分包括:山茶甙C,表儿茶素没食子酸酯,表阿福豆素,表儿茶素及表没食子儿茶素等5种。     

微波萃取茶叶中茶多酚的工艺改进

提出了微波萃取茶叶中茶多酚的改进工艺,以少量水作为茶叶湿润剂和主要的微波接受体,乙酸乙酯作为提取剂,对茶叶的茶多酚进行微波萃取,结果表明,新工艺对茶多酚提取率较高,所得的产品质量较好,且省时、节能显著.     

响应面法优化微波辅助提取豆腐柴果胶工艺及其抗氧化研究

豆腐柴含有丰富的果胶,具有多样的药理活性.在单因素试验基础上,以果胶提取率为指标,采用Box-Behnken优化其微波辅助提取工艺,并通过测定果胶对羟基自由基和超氧阴离子的清除率来研究豆腐柴果胶体外抗氧化活性.结果显示,豆腐柴果胶的最佳提取工艺为:微波功率635 W、提取时间29 s、液料比20:1(m L/g),该条件下果胶提取率平均值为20.31%.豆腐柴果胶对羟基自由基和超氧阴离子自由基有较强的清除作用,显示其具有良好的抗氧化活性.     

近红外光谱法对黔茶6种主要成分的快速测定

以贵州绿茶为研究对象,利用近红外光谱法对茶叶中水分、游离总氨基酸、咖啡碱、儿茶素类总量、茶多酚及水浸出物的含量进行快速同时测定。采用偏最小二乘法结合多元线性回归建立茶叶中水分、游离总氨基酸、咖啡碱、儿茶素类总量、茶多酚及水浸出物的定量校正模型,并用相关系数、交互验证均方差和预测均方差对模型进行评价,验证集中水分、游离总氨基酸、咖啡碱、儿茶素类总量、茶多酚及水浸出物6个内含物成分定量预测模型的相关系数分别为0.971 5、0.910 7、0.970 6、0.922 5、0.964 1、0.903 7;预测均方差(RMSEP)分别为0.574、0.418、0.279、0.959、0.735、0.28。结果表明,该方法简单、准确,更适合于茶叶中主要成分的快速分析。     

茶多酚的功效及提取工艺研究进展

茶多酚是茶叶中儿茶素类、黄酮类、酚酸类和花色素类化合物的总称。主要是儿茶素,因其化学结构中带有多个活性羟基,是一种目前不能人工合成的一种天然抗氧化剂,安全无毒,具有抑菌、杀菌、抗肿瘤、抗辐射等多种功效,作为医药和食品等的添加剂,其开发和应用前景十分看好。主要以茶多酚的提取方法和应用前景开展论述。     

唐古特白刺果油的Box-Behnken设计-效应面法优化微波辅助提取及成分分析

研究以石油醚为溶剂微波辅助提取唐古特白刺果油的工艺,并对其成分进行分析.采用响应曲面优化法(RSM)优化提取工艺,确定最佳提取工艺参数为提取微波功率460 W、提取时间10 min、液料比18∶1 (m L/g),在此条件下,唐古特白刺果油的提取率为5. 45%.利用GC-MS对唐古特白刺果油中脂肪酸成分进行分析,结果表明:唐古特白刺果油的主要脂肪酸成分为亚油酸(62. 99%)和油酸(27. 58%).     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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Brief Introduction to “Journal of Jilin University( Science Edition) ”

<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has