Effects of Solid Matrix and Porosity of Porous Medium on Heat Transfer of Marangoni Boundary Layer Flow Saturated with Power-Law Nanofluids

The effect of the solid matrix and porosity of the porous medium are first introduced to the study of power-law nanofluids, and the Marangoni boundary layer flow with heat generation is investigated. Two cases of solid matrix of porous medium including glass balls and aluminum foam are considered. The governing partial differential equations are simplified by dimensionless variables and similarity transformations, and are solved numerically by using a shooting method with the fourth-fifth-order Runge-Kutta integration technique. It is indicated that the increase of the porosity leads to the enhancement of heat transfer in the surface of the Marangoni boundary layer flow.

Rheological behavior of semi-solid Mg_2Si/AM60 magnesium matrix composites at steady state

The microstructure and rheological behavior of semi-solid Mg2Si/AM60 magnesium matrix composite at steady state were investigated.The results show that the primary α-Mg phases are knapped by mechanical stirring and the Chinese script type reinforced Mg2Si phases exist in liquid phase and grain boundary.The analysis of apparent viscosity indicates that the apparent viscosity of semi-solid Mg2Si/AM60 magnesium matrix composite at steady state increases with increasing the volume fraction of Mg2Si and solid fraction of primary α-Mg,but decreases with increasing the shearing rate and shearing time,and the apparent viscosity keeps stable when shearing time reaches 300 s.

Determination of Tebuconazole Residue in Apples and Vegetables by Matrix Solid Phase Dispersion-Gas Chromatography

[ Objective] The study aimed to determine tebuconazole residue in apples and vegetables using matrix solid phase dispersion-gas chro- matography （MSPD-GC）. [ Method] The effects of extraction and determination conditions on the detection of tebuconazole left in apples and veg- etables were analyzed, and the optimum extraction conditions were determined. [ Result] The recovery rate of tebucenazole was the highest when the ratio of a sample to florisil dispersant was 1 ： 4, and the mixture of hexane and acetone （ 1 ： 1 ） with total volume of 8 ml was as the eluant. Under the optimum conditions, the relative standard deviation （RSD） of the method was 4.9% -7.6%, and the detection limit was 0.1 tJg/g, while the re- covery rate of tebuconazole changed from 86.7% to 95. 2% . [ Conclusion] The method was simple, accurate, sensitive and applicable to the de- termination of tebuconazole in aaricultural Droducts.

Damage prediction for magnesium matrix composites formed by liquid-solid extrusion process based on finite element simulation

A damage prediction method based on FE simulation was proposed to predict the occurrence of hot shortness cracks and surface cracks in liquid-solid extrusion process.This method integrated the critical temperature criterion and Cockcroft & Latham ductile damage model, which were used to predict the initiation of hot shortness cracks and surface cracks of products, respectively.A coupling simulation of deformation with heat transfer as well as ductile damage was carried out to investigate the effect of extrusion temperature and extrusion speed on the damage behavior of Csf/AZ91D composites.It is concluded that the semisolid zone moves gradually toward deformation zone with the punch descending.The amplitude of the temperature rise at the exit of die from the initial billet temperature increases with the increase of extrusion speed during steady-state extrusion at a given punch displacement.In order to prevent the surface temperature of products beyond the incipient melting temperature of composites, the critical extrusion speed is decreased with the increase of extrusion temperature, otherwise the hot shortness cracks will occur.The maximum damage values increase with increasing extrusion speed or extrusion temperature.Theoretical results obtained by the DeformTM-2D simulation agree well with the experiments.

Elimination of matrix effects during analysis of perfluorinated acids in solid samples by liquid chromatography tandem mass spectrometry

Matrix effects can significantly hamper the accuracy and precision of the analysis results of perfluorinated acids(PFAs) in environmental solid samples.Several methods,such as standard addition,isotopically labeled internal standards,clean-up of SPE(solid phase extraction) eluents by dispersive graphitized carbon sorbent and substitution of eletrospray ionization(ESI) source by atmosphere pressure photoionization(APPI) source,were demonstrated for elimination of matrix effects in quantitative analysis of PFAs in solid samples.The results indicate that matrix effects can be effectively eliminated by standard addition,but instrumental analysis time will be multiplied.Isotopically labeled internal standards can effectively negate matrix effects of PFAs with the same perfluorocarbon chain length,but is not valid for the other analytes.Although APPI can eliminate matrix effects for all analytes,it is only suitable for analysis of high pollution levels samples.Clean-up of SPE eluents by dispersive graphitized carbon sorbent not only effectively negate the impact of matrix effect,but also avoid frequent clean of the ESI in order to maintain instrumental sensitivity.Therefore,the best method for elimination of matrix effects is the usage of dispersive graphitized carbon sorbent for clean-up of SPE elution.

Matrix Solid-phase Dispersion Extraction of Alkaloids from the Roots of Aconitum kusnezoffii Reichb

Matrix solid-phase dispersion（MSPD） was developed for the extraction of four alkaloids, including aconitine, mesaconitine, hypaconitine and deoxyaconitine, from the roots ofAconitum kusnezoffii Reichb. The determination of the analyte was carried out by high performance liquid chromatography with UV detection. The alkaline alumina was used as sorbent. The mixture of acetonitrile and water was used as elution solvent. Several extraction parameters, such as type of sorbent, the ratio of sample to solid support material, type of the elution solvent and the volume of the elution solvent were tested. Mean recoveries ranged from 93.16% to 102.73%, with relative standard deviations from 0.27% to 4.17%. With the extraction efficiency and time expenditure taken into account, MSPD extraction should be a comparatively good method.

Effect of interfacial reactions on solid erosion of Al_(18) B_4O_(33) whisker-reinforced AC4C Al alloy matrix composites

Solid erosion of as cast and treated 19.5%(volume fraction) Al 18 B 4O 33 whisker/AC4C Al composites was investigated at room temperature under steady state conditions. The results indicated that the interfacial reaction between the whisker and matrix alloy have an effect on the erosion characteristics of the composites. The erosion resistance of the composites with a strongly bonded whisker matrix interface and the higher whisker strength resulted from suitable reaction treatment can be improved at high impact angles and is the same as the as cast composites at low angle. For the composites after excessive reaction treatment, the weak and brittle interface fractures easily at small strains, and the whiskers with relative low strength and low hardness at the specimen surface can not effectively resist the microcutting or microploughing action, thus the composites exhibit reduced erosion resistance.

Determination of seven active components in Salvia miltiorrhiza herb by matrix solid phase dispersion combined with ion liquid extraction followed by high performance liquid chromatography

A low cost,rapid and sensitive preparation method of silica gel supported ionic liquid(SGSIL)combined with matrix solid phase dispersion(MSPD)followed by high performance liquid chromatography(HPLC)with ultraviolet detection(UV)is proposed,and it was applied to determine the seven active compounds in Salvia Miltiorrhiza herb.SGSIL and ionic liquid[BMIM]BF4 were used as the adsorbent and the green elution reagent in the MSPD procedure.Several extraction conditions including type of filler and elution solvent,the volume of elution solvent,material liquid ratio were optimized.Under the optimum conditions,the SGSIL-MSPD-HPLC method showed a low limit of detection(LOD,S/N=3)of 0.0122-0.8788μg/mL for standard solution,limit of quantification(LOQ,S/N=10)of 0.0406-2.9292μg/mL for standard solution,wide linear range from 1.56 to 2000μg/mL for all compounds for standard solution,correlation coefficients(r)of more than 0.9990,acceptable reproducibility(relative standard deviations,RSDs<3.54%),and precision of RSDs<3.36%for intra-day,RSDs<3.50%for inter-day.The satisfactory recoveries ranged from 96.4 to 102.5,with RSDs less than 3.45%.The developed SGSIL-MSPD method is easier and more suitable for the determination of the seven active compounds in Salvia Miltiorrhiza herb than the traditional ultrasonic extraction.It was an effective and efficient method for the extraction and quantification of the seven active compounds in traditional Chinese herbal samples.

INTERACTION OF PARTICLES WITH A SOLIDIFIED INTERFACE DURING SOLIDIFICATION OF METAL MATRIX COMPOSITE REINFORCED WITH PARTICLES

The interaction of particles with a solid-liquid interface during solidification of metal matrix composites has been investigated theoretically in this paper.Owing to the presence of particles in the melt,the shape of the solidification front and solute concentration field in front of solidification interface have been disturbed The thermodynamic method was employed,and a mathematical expression of the shape of the solidification interface and solute concentration field were deduced.Meanwhile,a theory is developed for evaluation of critical velocities of particles pushed by the solidification interface.A numerical simulation is done in which the critical velocity is evaluated as a function of particle size,thermal conductivity,diffusion coefficient,temperature gradient at the solidification front,the solid-liquid interfacial energy and the melt viscosity.The critical velocity is shown to be closely linked to the shape of the solidification interface and solute concentration field, and hence all the parameters also affect the shape of the solidification interface and solute concentration field of the front.

降雨入渗对防军隧道浅埋小净距段围岩稳定性的影响

为控制降雨入渗对浅埋小净距隧道围岩稳定性的影响,以义东高速公路防军隧道为依托,基于流固耦合理论和水土特征曲线,采用MIDAS GTS NX有限元软件建立浅埋小净距隧道数值模型,对雨季施工时的土体孔隙水压力、围岩变形特征和边仰坡安全系数展开分析。结果表明:随着降雨入渗的持续,围岩及边仰坡土体基质吸力逐渐减小,其土体抗剪强度也随之降低,稳定性变差。经过7 d累积降雨,孔隙水压力增大趋势逐渐放缓,围岩变形达到最大值,工况1的拱顶沉降增大了21.48%,且边仰坡安全系数小于1,处于失稳状态。洞口段采取加固和排水措施来控制围岩的稳定性,边仰坡的安全系数较加固前提升了17.27%,取得了良好的效果,保证了隧道后期的安全施工。

基于响应面法的基质固相分散萃取土壤中有机磷阻燃剂

有机磷阻燃剂(OPFRs)被广泛添加于商业品和日用品中,由于具有环境持久性、生物富集性和潜在毒性,已成为一种新兴的持久性有机污染物。因此需要建立能准确定量环境中OPFRs的检测方法。该文基于基质固相分散萃取(MSPD),结合气相色谱-串联质谱(GC-MS/MS)法测定土壤中10种有机磷阻燃剂,筛选对OPFRs具有高选择性的吸附剂,最终确定MSPD最佳萃取条件。该文基于单因素分析法考察了常见吸附剂(C18、PSA、Florisil、石墨化炭黑(GCB)和多壁碳纳米管(MWCNT))及其用量、洗脱溶剂及其体积、研磨时间对OPFRs萃取效率的影响。在此结果基础上,进一步利用响应面法(RSM)考察了3个关键因素(吸附剂用量、洗脱剂用量和研磨时间)以及交互作用对OPFRs萃取效率的影响。最终确定最优条件:吸附剂GCB,用量0.3 g;洗脱溶剂乙酸乙酯,用量10 mL;研磨时间5 min,此时10种OPFR的萃取效率为87.5%。在GC-MS/MS的多反应监测模式(MRM)下,以13C-PCB208为内标物进行定量。10种OPFRs在6个浓度梯度下,获得较好的线性,相关系数大于0.998。该方法的LOD和LOQ分别为0.006~0.161 ng/g和0.020~0.531 ng/g。在最佳条件下,加标土壤中OPFRs的加标回收率为70.4%~115.4%,相对标准偏差(RSD)为0.7%~6.7%。将该方法用于苏州不同功能土壤中OPFRs的含量测定,结果表明电子厂和汽修厂土壤中OPFRs总含量显著高于稻田土和校园土,电子厂和汽修厂土壤中主要污染物为磷酸三(2-氯异丙基)酯(TCIPP)、三苯基氧化膦(TPPO)、磷酸三(2-氯乙基)酯(TCEP)和磷酸三(1,3-二氯-2-丙基)酯(TDCPP),它们在电子厂土壤中含量分别为5.30、4.44、4.54、4.20 ng/g,在汽修厂土壤中的含量分别2.70、3.93、7.60、5.04 ng/g。目前关于TPPO的土壤污染报道较少,该研究在苏州工业区土壤中检出了高浓度TPPO污染。该方法成功用于土壤中10种OPFRs的检测。

磁性氮化碳复合材料的制备及其对磷酸化肽的富集

蛋白质的磷酸化在细胞信号传导和疾病发生发展中起着重要作用,但磷酸化的动态变化和低丰度的特点使得对其直接分析有着较大的困难。为了解决磷酸化肽难离子化、检测丰度低的瓶颈问题,本研究制备了一种磁性氮化碳复合材料,结合基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS),建立了一种对复杂样品中低丰度磷酸化肽富集与分析的方法。采用电子显微镜、红外光谱分析及X射线衍射分析等手段对合成的磁性氮化碳材料进行表征。以酪蛋白酶解产物为实验模型,发现磁性氮化碳材料能够实现对磷酸化肽的高选择性富集和高灵敏度检测,检出限为0.1 fmol。选择脱脂牛奶、人唾液和人血清为实际分析样品,发现磁性氮化碳材料对微量蛋白生物样品中磷酸化肽的分析具有较高的应用潜力。

SOLID MATRICES FOR EXPANDED BED ADSORPTION OF PROTEINS

Expanded bed adsorption (EBA) has been introduced as a primary recovery step for protein purification from a whole fermentation broth or unclarified cell homogenates. It can also be integrated with a fermentation or cell disruption process. Solid matrix is the principal pillar supporting the successful application of the EBA technology. This article summarizes the solid matrices employed in and developed for the EBA process to date. Further development of solid matrices for the expanded bed technique in the recovery of various biological substances from different sources has been addressed.

固体推进剂黏弹性参数的确定及细观损伤演化

固体推进剂力学模型参数的准确性对其宏观力学响应预测具有重要的意义,为解耦标定固体推进剂非线性黏弹性模型参数,提出一种基于台阶应力松弛试验的模型参数确定方法。通过台阶应力松弛平衡响应确定固体推进剂弹性部分参数,通过小变形下的应力松弛确定无量纲松弛模量,分析一种固体推进剂力学响应。研究结果表明:固体推进剂在台阶应力松弛及单轴拉伸条件下的力学性能预测结果与试验结果吻合,验证了所提方法的有效性;由于平衡响应包含损伤,采用该方法标定的参数可用于预测含损伤固体推进剂力学响应。在此基础上,提出一种基于推进剂模型参数标定等效黏合剂力学参数的方法,并通过引入基于黏弹性脱湿准则的相界面模型建立代表性体积单元计算模型,实现在宽应变(~100%)范围内推进剂脱湿损伤分析,为推进剂宏观力学性能预测及细观损伤演化分析提供了支撑。

基质固相分散辅助加速溶剂萃取-气相色谱-质谱法测定道路扬尘中9种邻苯二甲酸酯的含量

道路扬尘样品成分复杂且没有相应的标准检测方法,基于将加速溶剂萃取(ASE)与基质固相分散(MSPD)相结合,提出了题示方法。取10.0 g道路扬尘样品与10.0 g弗罗里硅土搅拌均匀,装入萃取池(预先加入一层厚度约0.5 cm的硅藻土),用体积比1\:1的正己烷-二氯甲烷混合液于100℃萃取2次。将萃取液浓缩至5.0 mL左右,氮吹至1.0 mL左右,用正己烷定容至1.0 mL,采用气相色谱-质谱法测定其中邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸二丙酯(DPRP)、邻苯二甲酸二异丁酯(DIBP)、邻苯二甲酸二丁酯(DBP)、邻苯二甲酸苄基丁基酯(BBP)、邻苯二甲酸二环己酯(DCHP)、邻苯二甲酸(2-乙基己基)酯(DEHP)和邻苯二甲酸正辛酯(DNOP)等9种邻苯二甲酸酯(PAEs)的含量。结果表明,9种PAEs标准曲线的线性范围均为0.1~5.0 mg·L^(-1),检出限(3.143 s)为1.10~1.39μg·kg^(-1)。按照标准加入法进行回收试验,回收率为76.6%~107%,测定值的相对标准偏差(n=6)小于10%。方法用于实际样品分析,DIBP、DBP和DEHP的检出量较高,依次为8.06~233μg·kg^(-1),23.9~3148μg·kg^(-1),16.5~4106μg·kg^(-1)。

超高效液相色谱-串联质谱法快速测定蔬菜中4种异噻唑啉酮类化合物的含量

提出了超高效液相色谱-串联质谱法(UHPLC-MS/MS)快速测定蔬菜中5-氯-2-甲基-4-异噻唑啉-3-酮(CMIT)、2-甲基-4-异噻唑啉-3-酮(MIT)、1,2-苯并异噻唑啉-3-酮(BIT)、2-正辛基-4-异噻唑啉-3-酮(OIT)等4种异噻唑啉酮类化合物含量的方法。取10.0 g已匀浆的蔬菜样品,用10 mL乙腈超声提取30 min,离心,残渣重复提取一次,合并提取液,加入5 g氯化钠,振荡、静置后,于40℃氮吹至近干,用2 mL 10%(体积分数,下同)甲醇溶液溶解残渣。所得溶液过已活化的HLB固相萃取小柱,用5 mL 10%甲醇溶液淋洗,6 mL甲醇洗脱。洗脱液于40℃氮吹至近干后,用甲醇定容至1 mL,过0.22μm有机滤膜,滤液在ACQIUTY UPLC BEH SHIELD RP18色谱柱上分离,以不同体积比的甲醇-水混合液为流动相进行梯度洗脱,质谱分析采用多反应监测采集模式,电喷雾正离子扫描模式,基质匹配法绘制工作曲线。结果表明,4种异噻唑啉酮类化合物的质量浓度在一定范围内与对应的峰面积呈线性关系,检出限(3S/N)分别为0.5,0.5,0.5,0.025μg·kg^(-1)。在不同蔬菜基质中进行3个浓度水平的加标回收试验,回收率为68.8%~81.3%,测定值的相对标准偏差(n=6)均小于9.0%。方法用于20种蔬菜样品分析,仅一组韭菜样品中检出BIT,检出量为2.3μg·kg^(-1)。

基于基质固相分散萃取-超高效液相色谱-串联质谱技术同时测定眼影和眉笔中5种防腐剂的含量

建立基质固相分散萃取-超高效液相色谱-串联质谱法检测眼影和眉笔中苯氧乙醇、脱氢乙酸、山梨酸、甲基氯噻唑琳酮和甲基氯异噻唑啉酮5种防腐剂的方法。样品与分散剂佛罗里硅土共研磨后,装入萃取小柱,用甲醇-丙酮洗脱萃取,对样品中防腐剂进行提取。采用超高效液相色谱-串联质谱的多反应监测模式(MRM)对5种防腐剂进行定性定量检测。这5种防腐剂在1~200μg/L均呈良好的线性关系,相关系数(R)均大于0.995,该方法检出限为0.003~0.008μg/g,定量限为0.009~0.024μg/g。该方法具有分离快速、操作简单、灵敏度高、重现性好、线性范围宽等优点,能解决眼影、眉笔等黏性易结块样品溶解不完全导致检测结果偏低的问题。

基质辅助固相萃取-GC-MS法快速测定水果中的肉桂醛

建立了测定水果中肉桂醛的气相色谱-质谱法。样品经乙酸乙酯提取后,上清液用50 mg PSA与20 mg GCB净化,经DB-5ms石英毛细柱(30 m×0.32 mm,0.25μm)分离后,采用GC-MS测定。结果表明,肉桂醛在25~500μg·L^(-1)线性关系良好,相关系数r^(2)为0.9995。苹果、香蕉、葡萄3种水果的方法检出限均为20μg·kg^(-1),方法定量限均为50μg·kg^(-1)。加标回收率为84.2%~101.0%,相对标准偏差为6.52%~8.77%。该方法定量准确,灵敏度及精密度均能满足水果中肉桂醛的测定要求。

用于复杂生物样品体系分离与识别的分子印迹技术最新进展

由生物样品中复杂组分所导致的基质效应会严重影响分离分析技术的准确性、灵敏度与可靠性。免疫亲和技术作为降低或消除基质效应的方法已被广泛应用于诊断分析和蛋白纯化等领域,但该技术仍存在明显的缺点,如成本高昂、制备流程繁琐、保存条件苛刻以及配体浸出等问题。目前,如何通过有效降低或消除复杂生物样品中的基质效应来实现痕量目标分析物的分离及识别仍是一个具有挑战性的问题。分子印迹技术(molecular imprinting technology,MIT)一直被广泛应用于固相萃取与色谱分离等领域,随着MIT的发展,各种新型印迹策略被提出;其中,分子印迹聚合物(molecularly imprinted polymer,MIP)作为一种能够模拟抗原-抗体间相互作用的高分子聚合物,可以从各种复杂生物样品中提取出目标分析物,从而有效消除基质效应的影响。MIP不仅拥有高特异性与高亲和力的优点,而且与抗体和适配体等生物大分子相比,MIP还具有稳定性高、成本低廉以及制备简便等优势。近年来一些基于MIT的传统分离技术得到了深入发展,其中包括色谱固定相以及固相萃取吸附剂等。此外,结合了MIT与高灵敏检测技术的分析方法在疾病诊断和生物成像等领域也受到了广泛关注。本文着重介绍了近年来发展的新型印迹策略,并介绍了基于MIP的分离分析方法在各领域中的应用以及现阶段存在的不足,最后对MIT的未来发展方向做出了展望。

微结构和添加剂改善金属基复合材料摩擦进展

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