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.

A Versatile Method for Uniform Dispersion of Nanocarbons in Metal Matrix Based on Electrostatic Interactions

Realizing the uniform dispersion of nanocarbons such as carbon nanotube and graphene in metals, is an essential prerequisite to fully exhibit their enhancement effect in mechanical, thermal, and electrical properties of metal matrix composites(MMCs). In this work, we propose an effective method to achieve uniform distribution of nanocarbons in various metal flakes through a slurry-based method. It relies on the electrostatic interactions between the negatively charged nanocarbons and the positively charged metal flakes when mixed in slurry. For case study, flake metal powders(Al, Mg, Ti,Fe, and Cu) were positively charged in aqueous suspension by spontaneous ionization or cationic surface modification. While nanocarbons, given examples as carboxylic multi-walled carbon nanotubes, pristine single-walled carbon nanotube, and carbon nanotube–graphene oxide hybrid were negatively charged by the ionization of oxygen-containing functional groups or anionic surfactant. It was found that through the electrostatic interaction mechanism, all kinds of nanocarbons can be spontaneously and efficiently adsorbed onto the surface of various metal flakes. The development of such a versatile method would provide us great opportunities to fabricate advanced MMCs with appealing properties.

Fast determination of multi-mycotoxins in corn by dispersive solid-phase extraction coupled with ultra-performance liquid chromatography with tandem quadrupole time-of-flight mass spectrometry

A fast analytical method for the simultaneous determination of 9 mycotoxins, including alfatoxins （B1, B2, G1, and G2）, fumonisins （B1, B2 and B3）, zearalenone, and deoxynivalenol in corn using dispersive solid-phase extraction method and ultra-performance liquid chromatography coupled to tandem quadrupole time-of-lfight mass spectrometry （UPLC-Q-TOF-MS） was developed and validated. Samples were extracted with acetonitrile-water （84：16, v：v, containing 1% acetic acid） using ultrasonic extraction. The extracts were puriifed with a dispersive SPE method using C18 as a cleaning agent. The ifnal clear extracts were dried by nitrogen blowing and subsequently redissolved in methanol-water （5：5, v：v）. The samples were then analyzed by UPLC-Q-TOF-MS with 0.1% formic acid in ammonium acetate-methanol as mobile phase. The mean recoveries were ranged from 68.0 to 120.0%, and the relative standard deviation （RSD） ranged from 0.18 to 6.29%. Limits of detections ranged from 0.05 to 50 μg kg？1, and limits of quantiifcation ranged from 0.1 to 200 μg kg？1, which were below the legal limits set by the European Union for the legislated mycotoxins. The developed method was applied to 130 corn samples. Among the mycotoxins studied, alfatoxins B1 and fumonisins B1, B2 and B3 were the most predominant mycotoxins, and their concentrations were 0–593.12, 0–2.01×104, 0–6.94×103 and 0–3.05×103 μg kg–1, respectively.

Trace determination and characterization of ginsenosides in rat plasma through magnetic dispersive solid-phase extraction based on core-shell polydopamine-coated magnetic nanoparticles

Enrichment of trace bioactive constituents and metabolites from complex biological samples is challenging.This study presented a one-pot synthesis of magnetic polydopamine nanoparticles(Fe3O4@-SiO2@PDA NPs)with multiple recognition sites for the magnetic dispersive solid-phase extraction(MDSPE)of ginsenosides from rat plasma treated with white ginseng.The extracted ginsenosides were characterized by combining an ultra-high-performance liquid chromatography coupled to a highresolution mass spectrometry with supplemental UNIFI libraries.Response surface methodology was statistically used to optimize the extraction procedure of the ginsenosides.The reusability of Fe3O4@-SiO2@PDA NPs was also examined and the results showed that the recovery rate exceeded 80%after recycling 6 times.Furthermore,the proposed method showed greater enrichment efficiency and could rapidly determine and characterize 23 ginsenoside prototypes and metabolites from plasma.In comparison,conventional methanol method can only detect 8 ginsenosides from the same plasma samples.The proposed approach can provide methodological reference for the trace determination and characterization of different bioactive ingredients and metabolites of traditional Chinese medicines and food.

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.

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.

Influence of nano-Al_2O_3-reinforced oxide-dispersion-strengthened Cu on the mechanical and tribological properties of Cu-based composites

The mechanical and tribological properties of Cu-based powder metallurgy （P/M） friction composites containing 10wt%-50wt% oxide-dispersion-strengthened （ODS） Cu reinforced with nano-Al2O3 were investigated. Additionally, the friction and wear behaviors as well as the wear mechanism of the Cu-based composites were characterized by scanning electron microscopy （SEM） in conjunction with energy-dispersive X-ray spectroscopy （EDS） elemental mapping. The results indicated that the Cu-based friction composite containing 30wt% ODS Cu exhibited the highest hardness and shear strength. The average and instantaneous friction coefficient curves of this sample, when operated in a high-speed train at a speed of 300 km/h, were similar to those of a commercial disc brake pad produced by Knorr-Bremse AG （Germany）. Additionally, the lowest linear wear loss of the obtained samples was （0.008 ± 0.001） mm per time per face, which is much lower than that of the Knorr-Bremse pad （（0.01 ± 0.001） mm）. The excellent performance of the developed pad is a consequence of the formation of a dense oxide composite layer and its close combination with the pad body.

High temperature tensile,compression and creep behavior of recycled short carbon fibre reinforced AZ91 magnesium alloy fabricated by a high shearing dispersion technique

The present study seeks the feasibility of using short carbon fibres recycled from polymer matrix composites as alternative to virgin carbon fibres in the reinforcement of magnesium alloys.The microstructures,high temperature mechanical and creep properties of AZ91 alloy and its composites with various recycled carbon fibre contents(2.5 and 5 wt.%)and lengths(100 and 500μm)were investigated in the temperature range of 25-200℃.The microstructural characterization showed that the high shear dispersion technique provided the cast composites with finer grains and relatively homogenous distribution of fibres.The materials tested displayed different behaviour depending on the type of loading.In general,while enhancements in the mechanical properties of composites is attributed to the load bearing and grain refinement effects of fibres,the fluctuations in the properties were discussed on the basis of porosity formation,relatively high reinforcement content leading to fibre clustering and interlayer found between the matrix and reinforcement compared to those of AZ91 alloy.The compressive creep tests revealed similar or higher minimum creep rates in the recycled carbon fibre reinforced AZ91 in comparison to the unreinforced AZ91.

PDRK:A General Kinetic Dispersion Relation Solver for Magnetized Plasma

A general,fast,and effective approach is developed for numerical calculation of kinetic plasma linear dispersion relations.The plasma dispersion function is approximated by J-pole expansion.Subsequently,the dispersion relation is transformed to a standard matrix eigenvalue problem of an equivalent linear system.Numerical solutions for the least damped or fastest growing modes using an 8-pole expansion are generally accurate;more strongly damped modes are less accurate,but are less likely to be of physical interest.In contrast to conventional approaches,such as Newton＇s iterative method,this approach can give either all the solutions in the system or a few solutions around the initial guess.It is also free from convergence problems.The approach is demonstrated for electrostatic dispersion equations with one-dimensional and twodimensional wavevectors,and for electromagnetic kinetic magnetized plasma dispersion relation for bi-Maxwellian distribution with relative parallel velocity flows between species.

Physical dispersion state and fluorescent property of Eu-complex in the Eu-complex/silicon rubber composites

The fluorescent complex Eu（TTA）2（Phen）（MA） （HTTA=2-Thenoyltrifluoroacetone, Phen=1,10-phenanthroline, MA=Maleic an- hydrider） was synthesized and characterized with elemental analysis, infrared spectrum （IR）, scanning electron microscope （SEM）, X-ray Diffraction（XRD）, differential scanning calorimetry（DSC）, and fluorescent measurement. To explore the effect of different physical dispersion state of Eu-complex on the fluorescent property of the Eu-complex/silicon rubber composites, various quantifies of Eu（TTA）2（phen） （MA） were mixed with silicon rubber （SIR） and peroxide to form uncured composites. These composites were vulcanized to obtain cured Eu-complex/SiR composites at 250 ℃, which was higher than the melting-point of Eu-complex. The SEM, XRD, DSC, and the fluorescent measurement of these composites showed that both the complex molecules dispersed in the silicon rubber during the melting process and the parent Eu-complex particles had positive effects on fluorescent property, whereas the re-crystallized Eu-complex particles and the aggregating complexes formed during the melting-process had negative effects on fluorescent property. For the uncured composites, their fluorescent intensities almost did not change with the increasing amount of Eu-complex. Furthermore, for the composites with small content of Eu-complex, their fluorescent intensities decreased significantly after curing, and this difference in fluorescent intensity became smaller as the content of Eu-complex increases.

Formation of composites fabricated by exothermic dispersion reaction in Al-TiO_2-B_2O_3 system

The formation of aluminum matrix composites fabricated by exothermic dispersion reaction in Al-TiO2-B2O3 system was investigated. The thermal analysis results show that the reactions are spontaneous and exothermic. The Gibbs free energy of α-Al2O3 is the lowest among all the combustion products, followed by TiB2 and Al3Ti. It is noted that when the B2O3/TiO2 mole ratio is below 1, the reaction products are composed of particle-like α-Al2O3, TiB2 and rod-like Al3Ti. The α-Al2O3 crystallites, resulting from the reaction between Al and TiO2 or B2O3, are segregated at the grain boundaries due to a lower wettability with the matrix. SEM micrographs show that rod-like Al3Ti phase distributes uniformly in the matrix. When the B2O3/TiO2 mole ratio is around 1, the Al3Ti phase almost disappears in the composites, and the distribution of α-Al2O3 particulates is improved evidently.

A New Approach for Dispersion Parameters

This paper presents a new approach to identify and estimate the dispersion parameters for bivariate, trivariate and multivariate correlated binary data, not only with scalar value but also with matrix values. For this direction, we present some recent studies indicating the impact of over-dispersion on the univariate data analysis and comparing a new approach with these studies. Following the property of McCullagh and Nelder [1] for identifying dispersion parameter in univariate case, we extended this property to analyze the correlated binary data in higher cases. Finally, we used these estimates to modify the correlated binary data, to decrease its over-dispersion, using the Hunua Ranges data as an ecology problem.

水下抗分散水泥土正交试验及配比优化方法研究

水流经过桩基时会形成漩涡侵蚀床面,影响桩基及上部结构的稳定性,冲刷治理是工程界关注的热点问题。为促进固化土技术在桩基冲刷修复中的应用,设计开展了抗分散水泥固化土系列正交试验。针对高岭土和淤泥土,选用PAM、EVA、黄原胶、HPMC四种抗分散剂,采用平均效果分析和极差分析,研究了抗分散剂种类、抗分散剂掺量、含水量和水泥掺量对流动度、浊度、7 d和28 d无侧限抗压强度的影响。结果表明:对于高岭土,抗分散剂掺量从0.25‰增大到1‰,水泥土流动度减小20%,浊度减小25%,抗分散剂掺量对流动性和抗分散性的影响显著。对于淤泥土,对抗分散性影响显著的仍是抗分散剂掺量,而对流动性的影响显著的则是含水量,含水量从1.4倍液限增大到2.0倍液限,水泥土流动度增大45%。基于综合平衡法、矩阵分析法和多元线性回归模型,提出了一种抗分散水泥土配比设计方法,研究得到了高岭土和淤泥土抗分散水泥固化土的推荐配比,其在泥沙起动实验中的抗冲刷特性明显优于原始土样。

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。

Development of matrix solid-phase dispersion method for the extraction of short-chain chlorinated paraffins in human placenta

Chlorinated paraffins（SCCPs） are widely used worldwide, and they can be released into the environment during their production, transport, usage and disposal, which pose potential risks for human health. In this work, an efficient, reliable and rapid pretreatment method based on matrix solid-phase dispersion（MSPD） was developed for the analysis of short-chain CPs（SCCPs） in human placenta by gas chromatograph-electron capture negative ion low-resolution mass spectrometry（GC-ECNI-LRMS） and gas chromatography–quadrupole time-of-flight mass spectrometry（GC–QTOF-HRMS）. The MSPD-relevant parameters including dispersing sorbent,sample-to-sorbent mass ratio, and elution solvent were optimized using the orthogonal test.Silica gel was found to be the optimal dispersing sorbent among the selected matrices. Under the optimal conditions, 44% acidic silica gel can be used as the co-sorbent to remove lipid and eluted by the mixture of hexane and dichloromethane（7：3, V/V）. The spiked recoveries of the optimized method were 77.4% and 91.4% for analyzing SCCPs in human placenta by GC-ECNI-LRMS and GC–QTOF-HRMS, and the corresponding relative standard deviations were10.2% and 5.6%, respectively. The method detection limit for the total SCCPs was 36.8 ng/g（dry weight, dw） and 19.2 ng/g（dw） as measured by GC-ECNI-LRMS and GC–QTOF-HRMS,respectively. The concentrations of SCCPs in four human placentas were in the range of

基于多元精细复合多尺度波动散布熵和累积欧氏距离矩阵测度的风电机组变桨轴承退化状态评估

针对风电机组变桨轴承服役过程环境噪声干扰严重、退化状态评估精度低的问题,提出一种基于多元精细复合多尺度波动散布熵和累积欧氏距离矩阵测度的退化状态评估模型。该模型将监测数据状态特征获取过程由单通道拓展为多通道进行,通过提出的多元精细复合多尺度波动散布熵算法来获取多通道监测数据的多尺度状态特征,并将累积和检验算法与欧氏距离矩阵测度方法相结合,用于定量衡量基准样本与待分析样本间的差异,从而实现变桨轴承退化状态评估。风电机组变桨轴承全寿命周期加速疲劳实验验证结果表明:该模型能够及时捕捉到变桨轴承的初始退化时刻并且准确跟踪整个退化过程。

不确定转子系统动力学降阶模型构建与模型散度参数辨识

在航空、航天、船舶等领域的实际工程转子系统中,广泛存在高维复杂的非线性系统。在航空发动机转子系统、燃气轮机转子系统等重点研究领域,通常还难以对高维复杂非线性系统进行直接的数据处理和分析统计。针对不确定性转子系统的模型维度较高等问题,提出了一种模型不确定性动力学降阶计算模型构建和模型散度参数辨识方法。首先,根据确定性动力学模型和静态矩阵降阶方法,完善了确定性动力学降阶模型;然后,基于随机矩阵理论和非参数动力学建模方法,提出了不确定性动力学降阶模型;最后,利用系统确定性模型的一阶临界转速、振型和实验数据,对不确定性动力学模型的散度参数进行了辨识;为了验证散度参数辨识方法的有效性,笔者又在转子实验平台上进行了实验验证。研究结果表明:实验结果与降阶之后振动响应均值的差异性较小,且与不确定性动力学模型相差不超过10%,表明所采用的理论模型在描述转子系统行为方面具备了较高的准确性和可靠性,该模型可以为深入研究模型不确定性转子系统提供参考。

粉末冶金制备碳纳米管增强铜基复合材料研究进展

碳纳米管具有优异的力学性能和导电、导热性能,作为增强体引入铜基体中有望开发出新一代高强、结构功能一体化的复合材料。然而,碳纳米管在铜基体中的分散性较差及其与铜的润湿性问题,成为制备碳纳米管增强铜基(CNTs/Cu)复合材料的主要挑战,并显著影响了复合材料的性能。本文对目前有关制备碳纳米管增强铜基复合材料的主要方法包括碳纳米管前期预处理方法、碳纳米管在铜粉末中分散的方法、复合材料的烧结方法进行总结,概述复合材料的力学性能、摩擦磨损性能以及导电导热性能的研究进展,并提出思考和展望,以便为制备CNTs/Cu复合材料研究提供参考。

钛基石墨烯复合材料的分散性、界面结构及力学性能

石墨烯由于独特的结构和优异的力学、导电、润滑等性能,被认为是理想的金属基复合材料的增强体。将石墨烯作为增强体增强钛基复合材料有着巨大的应用潜力。然而,石墨烯的分散性及其与钛基体的反应是制约获得高性能石墨烯增强钛基复合材料的难点。本文综述了钛基石墨烯复合材料的分散性、界面及力学性能的研究进展。钛基石墨烯复合材料通常采用粉末冶金法制备,石墨烯能较均匀地分散于复合材料组织中,但当石墨烯添加量过多时仍会出现团聚现象。石墨烯与钛基体易发生反应生成TiC,通过固化烧结工艺的改进、基体复合化、石墨烯表面改性以及原位自生等方法可以有效地抑制界面反应并提高界面结合力。随着石墨烯含量的增加,钛基石墨烯复合材料的压缩、拉伸强度与硬度一般呈现先增大后减小的趋势。石墨烯增强钛基复合材料的强化机制通常以载荷传递强化为主,但有些情况下由石墨烯引起的位错强化、细晶强化及奥罗万(Orowan)强化效果也较为显著。