栾树叶总多酚的超声波辅助提取工艺及其抗氧化活性北大核心

以10 g栾树叶粉末为原料,在单因素试验基础上,采用响应面法优化栾树叶总多酚超声波辅助提取工艺,以乙醇体积分数、液料比、提取时间、提取温度、超声波功率为因子,总多酚质量分数、总多酚得率为响应值,得到优化提取条件为乙醇体积分数72%、液料比25∶1(m L∶g)、提取时间15 min、提取温度60℃、超声波功率200 W以及提取3次。在此条件下,栾树叶粗提物总多酚质量分数为61.26%、总多酚得率为3.41%。抗氧化实验结果表明:栾树叶粗提物清除1,1-二苯代苦味酰基(DPPH)自由基能力显著高于BHT和Vc,IC_(50)值为103.78 mg/L;栾树叶粗提物的铁离子还原能力与BHT相当,明显高于Vc。     

栾树叶总多酚的超声波辅助提取工艺及其抗氧化活性

以10g栾树叶粉末为原料,在单因素试验基础上,采用响应面法优化栾树叶总多酚超声波辅助提取工艺,以乙醇体积分数、液料比、提取时间、提取温度、超声波功率为因子,总多酚质量分数、总多酚得率为响应值,得到优化提取条件为乙醇体积分数72%、液料比25:1(mL:g)、提取时间15 min、提取温度60℃、超声波功率200 W以及提取3次。在此条件下,栾树叶粗提物总多酚质量分数为61.26%、总多酚得率为3.41%。抗氧化实验结果表明:栾树叶粗提物清除1,1-二苯代苦味酰基(DPPH)自由基能力显著高于BHT和Vc,IC₅₀值为103.78 mg/L;栾树叶粗提物的铁离子还原能力与BHT相当,明显高于Vc。     

响应面法优化花生壳中白藜芦醇提取工艺及其抗氧化活性研究

以单位质量花生壳中白藜芦醇含量为响应值,乙醇体积分数、提取温度和提取时间为响应变量,用响应面法(RSM)确定最佳工艺条件,测定白藜芦醇粗提物对1,1-二苯基-2-三硝基苯肼(DPPH)自由基和羟自由基的清除率,用半抑制率(IC50)评价其抗氧化活性。结果表明,最佳提取条件为:乙醇体积分数62%,提取温度41℃,提取时间91 min,料液比1∶20 g/m L。在此条件下,白藜芦醇的提取量1.054 mg/g,与模型预测值1.041 mg/g基本符合。DPPH自由基和羟自由基的IC_(50)分别为(0.970±5.862)mg/m L,(0.188±2.911)mg/m L。研究表明,花生壳可以作为白藜芦醇的来源,且白藜芦醇具有较好的抗氧化活性。     

响应面法优化花生壳中白藜芦醇提取工艺及其抗氧化活性研究

以单位质量花生壳中白藜芦醇含量为响应值,乙醇体积分数、提取温度和提取时间为响应变量,用响应面法(RSM)确定最佳工艺条件,测定白藜芦醇粗提物对1,1-二苯基-2-三硝基苯肼(DPPH)自由基和羟自由基的清除率,用半抑制率(IC50)评价其抗氧化活性。结果表明,最佳提取条件为:乙醇体积分数62%,提取温度41℃,提取时间91 min,料液比1∶20 g/m L。在此条件下,白藜芦醇的提取量1.054 mg/g,与模型预测值1.041 mg/g基本符合。DPPH自由基和羟自由基的IC_(50)分别为(0.970±5.862)mg/m L,(0.188±2.911)mg/m L。研究表明,花生壳可以作为白藜芦醇的来源,且白藜芦醇具有较好的抗氧化活性。     

响应面法优化石韦多糖提取工艺及其体外抗氧化活性研究

采用水提醇沉法提取石韦多糖,利用苯酚-硫酸法测定多糖质量分数,以石韦多糖得率为指标通过响应面法优化提取工艺,通过DPPH自由基清除率评价石韦多糖的抗氧化能力。结果表明：石韦多糖的最佳提取料液比为1∶27 g·m L^-1、提取时间为110 min、提取温度为76℃,在此条件下石韦多糖的得率为3.96%,对DPPH自由基的半数清除质量浓度(IC50)为0.445 mg·L^-1,与阳性对照维生素Vc比较,石韦多糖具有良好的抗氧化活性。     

响应面法优化红薯叶多酚超声辅助提取工艺及其抗氧化活性研究

以红薯叶多酚提取率为评价指标,以提取温度、乙醇体积分数、料液比、提取时间为考察因素,在单因素实验的基础上,采用响应面法优化红薯叶多酚的超声辅助提取工艺,并通过测定红薯叶多酚对DPPH自由基、ABTS自由基的清除能力,评价其抗氧化活性.确定红薯叶多酚的最佳提取工艺为:提取温度61℃、乙醇体积分数72％、料液比1:21(g...     

黄香楝中黄酮、多酚的提取工艺

利用水浴-回流法提取黄香楝中的黄酮、多酚,并用分光光度法分析其含量。研究了不同乙醇体积分数、液料比、提取温度、时间对样品中黄酮、多酚提取效率的影响。通过实验得出黄香楝中黄酮和多酚提取的最优工艺为:提取温度为85℃,料液质量浓度比为1∶45,时间为4 h,乙醇体积分数为50%。在此条件下黄香楝中黄酮、多酚能够被同时提取,此操作简单、稳定性好、结果准确。黄香楝多酚和黄酮含量分别为4. 85、4. 79 mg/g。结果表明,水浴-回流法能够同步提取黄香楝中的黄酮、多酚类物质。     

响应面法优化秦艽多酚提取工艺及体外抗氧化活性研究

以乙醇体积分数、超声时间、料液比及超声功率为考察因素,以秦艽多酚得率为考察指标,进行单因素实验,在此基础上采用响应面法优化秦艽多酚提取工艺。选取维生素C(VC)作为阳性对照,考察秦艽多酚对DPPH自由基及ABTS自由基的清除能力,评价其体外抗氧化活性。确定秦艽多酚的最佳提取工艺为:料液比1∶21(g∶mL)、乙醇体积分数40%、超声时间50min、超声功率140W,在此条件下,秦艽多酚得率为1.012%。秦艽多酚具有一定的体外抗氧化活性,秦艽多酚和VC抑制DPPH自由基的IC50分别为13.590μg·mL~(-1)和5.757μg·mL~(-1);秦艽多酚和VC抑制ABTS自由基的IC50分别为3.275μg·mL~(-1)和3.419μg·mL~(-1)。该提取工艺稳定、可行。     

枇杷果肉总多酚提取及体外抗氧化活性研究

目的:以枇杷果肉为研究对象,辅以超声波法提取总多酚。方法:通过正交试验确定最优提取工艺条件:提取温度为60℃,料液比1:35(g·mL~(-1)),乙醇体积分数60%,超声提取时间18 min,总多酚提取率达0.94%。通过1,1-二苯基-2-苦肼基(DPPH·)清除率的测定对枇杷果肉总多酚进行体外抗氧化活性评价。结果:枇杷果肉总多酚DPPH·清除率明显高于维生素C(Vc),且枇杷果肉总多酚DPPH·半数抑制浓度(IC50=7.04μg·mL~(-1))优于Vc(IC50=7.70μg·mL~(-1))。结论:枇杷果肉总多酚是一种天然的抗氧化活性剂。     

响应面法优化海带中总多酚提取工艺及抗氧化活性

采用响应面法优化海带总多酚提取工艺,以海带总多酚对二苯代苦味酸(DPPH)自由基的清除作用来评价其抗氧化活性。结果表明,海带总多酚最佳提取工艺是:提取温度72℃,乙醇体积分数52%,液固比60∶1 m L/g,提取时间40 min。在此条件下,海带总多酚提取率达0.945 mg/g,与理论值0.954 mg/g的相对误差为-0.94%。海带总多酚提取液对DPPH自由基有明显的清除作用,其抗氧化性效果随着提取液浓度的增加而增大,且在同等条件下,海带总多酚对DPPH自由基的清除作用优于没食子酸。说明海带总多酚具有较好的抗氧化作用,是一种优良的天然抗氧化剂。     

乙烯酮(双乙烯酮)下游产品废水的治理技术

乙烯酮(双乙烯酮)是十分重要的化工中间体,其下游产品较多。江苏某化工厂开发生产乙烯酮(双乙烯酮)下游产品三十多个,年生产规模三万多吨,是国内以乙烯酮(双乙烯酮)为中间体生产精细化学品的综合骨干企业。针对乙烯酮(双乙烯酮)下游产品废水特点,该厂结合企业实际,开展了产品优化,结构调整,清洁生产,资源循环利用,节水降耗等工作,从源头削减了污染物的生产。同时投资二千多万元新建预处理装置三套,6000m3/d废水生化处理装置一套,使全厂乙烯酮(双乙烯酮)下游产品的废水得到了有效的治理。     

几种乙炔加压设备性能的比较

阐述并比较了几种加压设备在乙炔加压清净过程中的性能和特点。     

三种煤样燃烧热的测定

本文通过三个厂家提供的三种煤样燃烧热的测定,由测定结果综合得出3号煤样燃烧最完全、燃烧热也最大,是三个煤样中最好的一种。     

Semi-empirical equation of state of metals. Equation of state of aluminum

A semi-empirical equation of state for metals is described. Its capabilities are demonstrated by the example of the equation of state for aluminum. New experimental data are presented on the location of the isentrope of aluminum for unloading from the state at p = 229.71 GPa on the shock adiabat to an aerogel (SiO₂) of density 0.08 g/cm³. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 61–75, March–April, 2008.     

水泥水化热测定方法综述

水泥水化热是中、低热水泥和核电工程用水泥的一项关键的技术指标。全球范围内测定水泥水化热的方法有溶解法、直接法/半绝热法、等温传导量热法三种。本文总结了中、美、欧相关方法标准,对其测试原理、仪器设备、试验过程等方面进行了比对,并对其在领域的应用做了简单的概括。     

小议汽车涂装工艺设计对涂装成本的影响

论述了涂装工艺设计对涂装设备投资、涂装生产成本的影响。     

Measurement of the gradient of viscosity with composition of mixtures of non-ideal gases

A perturbation viscometer is a differential capillary viscometer that measures the logarithmic viscosity gradient of the viscosity-composition curve for gas mixtures. Measurements are made at different gas mixture compositions. Integration of the logarithmic viscosity gradients measured over the full composition range gives the mixture viscosity relative to the viscosity of one of the pure components of the gas mixture. This method is attractive because, for measurements of equal precision, integration of the gradients is potentially an order of magnitude more precise than measurement of the viscosities directly. It can also work at high and low temperatures and perhaps high pressures.The perturbation viscometer has been used to make measurements on ideal gas mixtures at ambient and elevated temperatures. The situation is more complicated when the gas mixtures are non-ideal. Extra effects due to density differences, molar volume change on mixing and differential thermal expansion may be measured in addition to the desired viscosity change producing systematic errors in the results. Thus, a more sophisticated apparatus is required. The standard perturbation viscometer has been modified to separate out the extra effects to permit measurement of the true change in viscosity. In addition, the theoretical operation of the modified apparatus has been revised to account for the design changes to permit calculation of the viscosity-composition profiles from the results.The apparatus has been tested using helium-HFC-125 mixtures and two new viscosity-composition profiles are presented for these mixtures at 23 and . Internal consistency tests have been used to confirm that the data produced are of high quality with an estimated uncertainty in the viscosity ratio data at of 0.9% and at of 1.5%.     

Calorimetric and Computational Study of Enthalpy of Formation of Diperoxide of Cyclohexanone

A thermochemical rather simple experimental technique is applied to determine the enthalpy of formation of Diperoxide of ciclohexanone. The study is complemented with suitable theoretical calculations at the semiempirical and ab initio levels. A particular satisfactory agreement between both ways is found for the ab initio calculation at the 6–311G basis This set level. Some possible extensions of the present procedure are pointed out.     

塔设备改造选型的分析

就当前扩产增容中塔设备设计和改造时板式塔和填料塔的选型问题加以分析。在评述目前国内常用的几种塔板和新型填料之后，着重介绍一种新型塔板（导向梯形浮阀塔板）和一种新型填料（波环填料——乾隆帕克）。     

Effect of degree of deacetylation of chitin on the properties of chitin crystallites

In the present article, chitin from crab shell was systematically deacetylated using a NaOH treatment with control of the reaction time. The degree of deacetylation, monitored using solid-state NMR, revealed that the reaction was pseudo-first order. Based on this, swollen and NaOH-saturated particles are proposed as the reaction system. The weight loss of the partially saponified and neutralized samples after HCl hydrolysis increased linearly with the degree of deacetylation. The crystallinity of the samples was found to increase after acid hydrolysis. According to conductimetric titration, the surface charge density of the crystallites, after acid hydrolysis, was found to increase with base treatment time. The effect of surface charge on the formation of a chiral nematic phase, due to the rodlike nature of the crystallites, was explored. These results show that because the contribution of charged particles to the ionic strength was significant the double layer compression was affected, especially since the surface charge density was close to the Manning limit. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:373–380, 1997