应用蚕豆根尖微核试验测定维生素C的抑突变性

目的:了解水果蔬菜中维生素C的抑突变性.方法:应用荧光法测定水果、蔬菜中维生素C的含量,蚕豆根尖微核技术检验维生素C的抑突变性.结果:9种水果蔬菜的维生素C含量为(39.19±29.65)mg/100 g,蚕豆根尖微核率(MCN‰)与阳性对照比较均有统计学意义(P<0.05).结论:水果、蔬菜中的维生素C对诱变中的蚕豆根尖细胞有一定的抑突变性,且抑制细胞突变与水果、蔬菜中维生素C的含量有剂量一效应关系.维生素C越高,抑突变的效应越明显.     

水温对饮料中维生素C含量的影响

采用紫外分光光度法,Cu2 做催化剂氧化抗坏血酸(还原型维生素C),差值法消除样品中其他成分的干扰吸收,检测了不同温度水冲泡卡夫柠檬C冲剂得到的溶液中还原型维生素C含量的差别.结果显示,冲泡冲剂所用的水温越高,得到的溶液中还原型维生素C越少,对维生素C的有效摄取有显著影响.     

紫外分光光度法测定维生素C

维生素C是一种对人体重要的物质.人体严重缺乏维生素C将引起坏血病.维生素C的含量测定中国药典1995年版采用碘量法[1],需标定滴定液磺,麻烦费时,基准物毒性大.光度法测定维生素C的方法很多[2～6].     

二阶导数光谱法测定非酶褐变反应中抗坏血酸的含量

在抗坏血酸—氨基酸的体系中探讨发生非酶褐变反应后的抗坏血酸含量的测定方法.用偏磷酸溶液作为提取剂,采用二阶导数光谱法测定了非酶褐变反应中的抗坏血酸含量.测定的线性范围1.00~12.00μg/mL,回归方程:C=6 721.304A-0.058 8,线性相关系数为γ=0.999 9,加标回收率96.50%~103.75%.该方法简便,干扰小,适合发生了非酶褐变反应的体系中的抗坏血酸含量的测定.     

Q&A

<正>Q:吃水果可以代替吃蔬菜吗?(读者:傅天任)A:水果和蔬菜在营养上各有特点,是不能相互取代的。蔬菜对健康尤为重要,不能用水果代替。通常来说,蔬菜所含的无机盐(矿物质)和维生素要比水果丰富。特别是绿叶菜,维生素C、胡萝卜素、膳食纤维以及铁、钙等矿物质的含量丰富。而除了柑橘、猕猴桃、草莓、枣、山楂等之外,常见水果的矿物质与维生素C含量都比蔬菜少。蔬菜中维生素A和B、胡萝卜、素等的含量也高于水果。     

RP-HPLC直接测定水果中维生素C含量

应用反相高效液相色谱法对时令水果中维生素C含量进行直接测定.方法: 色谱柱Eclipse XDB-C18 (5 μm 4.6×250 mm);流动相乙腈-水(40∶ 60 v/v);流速1.0 mL/min;检测波长275 nm.实验结果表明维生素C在(10 ～ 640) μg/mL范围内呈良好线性,R2=0.999 96,回收率为99.3% ～ 104.5%,RSD=1.65%.本法操作简便,结果准确、重现性好,为测定水果中维生素C的含量提供了一种有效方法.     

库仑滴定法测定水果、蔬菜中Vc含量的研究

以1mol·L-1碘化钾和1mol·L-1磷酸(1∶1VV)为电解液,在阳极电生I2与抗坏血酸分子中—CC—不饱和双键发生加成反应,据此以恒电流库仑滴定法进行抗坏血酸的定量测定.测定了多种水果及蔬菜中抗坏血酸含量并与文献方法(碘量法)相对比,结果表明,本法具有设备简单、快速、灵敏,更准确等优点.     

毛细滴管数滴法测定几种果蔬中维生素C含量研究

以自制的液滴体积为0.01～0.02mL的聚乙烯毛细滴管对果蔬中维生素C的含量进行数滴分析，其主要仪器外形小巧、便于携带，滴定快速、准确，试剂消耗量约为常量法的1／20，滴定剂用量约为30～150滴，维生素C含量不确定度Urel（C）为0.56％，与常量法相当，相对标准偏差比常量法略小。该法克服了常量法中滴定管、移液管、铁架台和蝴蝶夹等仪器携带不方便的不足，适用于水果、蔬菜、饮料等维生素含量的快速分析。     

用氧化锌代替氯化锌测定乙二胺四乙酸和乙二胺四乙酸二钠的含量

1.前言国家标准GB/T1401-1998乙二胺四乙酸二钠和行标HG/T3457-1976乙二胺四乙酸的含量测定方法规定用氯化锌作为标准滴定溶液。氯化锌标准溶液必须用乙二胺四乙酸二钠标准滴定溶液进行间接滴定,而乙二胺四乙酸二钠标准滴定溶液是用氧化锌基准物进行标定。这种方法既费时又麻烦,在间接标定过程中存在的系统误差大。本文介绍用工作基准试剂(容量)氧化锌代替氯化锌直接作为标准滴定溶液,既省事又准确,收到良好的效果。     

L-赖氨酸修饰玻碳电极测定维生素C片中抗坏血酸含量的研究

文章研究了L-赖氨酸修饰玻碳电极的制备,采用快速循环伏安法测定维生素C片剂中抗坏血酸含量,并对实验条件进行了选择。结果表明,在pH值为4.8的磷酸盐缓冲溶液中测抗坏血酸浓度时,其线性形范围为0.0600～0.6000g.L-1,R2=0.9872。该修饰电极用于抗坏血酸含量的分析,有良好的稳定性和抗干扰能力,结果令人满意。     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

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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