基于气相离子迁移谱技术分析延安市不同县区的富士苹果挥发性成分的差异

目的 分析比较延安市不同区县富士苹果之间挥发性成分的差异。方法 采用气相离子迁移谱(gas chromatography-ion mobility spectrometry,GC-IMS)技术对延安市13个县区的晚熟富士苹果的挥发性成分进行分析,建立富士苹果的挥发性成分特征指纹图谱,并进行主成分法和聚类分析法分析。结果 在延安市13个县区富士苹果样品中共鉴别出的挥发性成分54种,主要有酯类、醇类、酮类、醛类和酸类等物质,各县区富士苹果的酯类和醇类物质占比较高,分别占总挥发性成分的48.98%~53.19%和13.04%~19.23%。13个县区富士苹果共有的挥发性成分有2-乙基呋喃、丙酸乙酯、甲酸异戊酯、乙酸己酯、乙酸异戊酯、2-甲基丁基乙酸酯等,这些物质共同奠定了延安富士苹果香气的总体基调,各县区富士苹果的挥发性成分的具体种类和含量各有不同。结论 本研究通过建立挥发性成分特征指纹图谱,明确了延安市不同区县富士苹果之间挥发性成分存在的差异。研究发现延安市宝塔区的富士苹果挥发性成分种类及含量较丰富,其特征性物质有巴豆酸乙酯、异丙醇、2,3-丁二酮、乙酸甲酯等。黄陵县富士苹果特有丁酸丙酯、丁酸甲酯等物质。宜川县富士苹果的特征性物质有反式-2-已烯醛、丁酸异戊酯、丁酸等。此外富县富士苹果中含量丰富的挥发性成与黄陵县富士苹果的部分挥发性成分一致。延川、洛川县、甘泉县、黄龙县和吴起县的富士苹果中含量丰富的挥发性成分较为相似;子长市、安塞区、志丹县、延长县的富士苹果中含量丰富的挥发性成分较为相似。结果表明GC-IMS技术在延安市富士苹果的挥发性成分的分析方面具有较好的应用价值,可用于不同县区富士苹果的风味识别和品质评价。     

Rapid and Sensitive Liquid Chromatography-Tandem Mass Spectrometry for Quantification of Glycyrrhetic Acid in Human Plasma

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometry(LC-MS/MS) for the determination of glycyrrhetic acid in human plasma with ginsenoside Rh2 as internal standard was developed and validated. The plasma samples were prepared via liquid-liquid extraction with ethyl acetate. Chromatographic separation was accomplished on a Venusil MP-C18(50 mm×2.1 mm, 5μm i.d.) column at 25℃. The mobile phase consisted of acetonitrile/5 mmol·L-1 ammonium acetate(10:90, volume ratio) at a flow rate of 0.4 mL/min. Negative electrospray ionization was utilized as the ionization source. Glycyrrhetic acid and internal standard were determined via the mutiple reaction monitoring of precursor→production ion transitions at m/z 469→425, 409 and m/z 621→161,respectively. Each sample was chromatographed within 2.5 min. The lower limit of uantification was 0.50 ng/mL for 200 μL of plasma sample and the linear range was from 0.50 ng/mL to 800 ng/mL. The intra-and inter-day precisions were less than 8.76% in terms of relative standard deviation(RSD), and the accuracy was within a range of -3.25%-1.32% in terms of relative error(RE). The method was successfully applied to the pharmacokinetic studies of glycyrrhetic acid in healthy male Chinese volunteers after a single oral administration of 75 mg of glycyrrhizin.     

浓缩硼同位素的化学提纯与质谱分析

一、引言 在核燃料循环中,准确地测定硼同位素丰度及确定核燃料产品中硼含量具有重要意义。 关于硼的化学提纯方法有蒸馏法、萃取法,离子交换法,汞阴极电解法等,其中蒸馏法能使硼与其他杂质元素分离比较完全,而且,操作简便、重复性好、适应范围广。本工作用蒸馏法提纯浓缩硼元素获得了比较满意的结果。     

SPS烧结M42粉末冶金高速钢的显微组织与性能

采用放电等离子烧结技术(SPS)制备了M42粉末冶金高速钢,研究了SPS烧结M42粉末冶金高速钢及其热处理后的显微组织与性能。结果表明:与普通粉末冶金高速钢相比,SPS烧结制备的M42粉末冶金高速钢显微组织均匀、晶粒细小、无碳化物偏析。经过在1180℃×5min×550℃×1h的热处理后,硬度比普通粉末冶金高速钢提高1～2HRC。     

TiB_2/ZrB_2/SiC复合功能材料的微观结构与力学性能

采用放电等离子烧结工艺,制备TiB2/ZrB2/SiC复合功能材料。用X射线衍射仪和场发射扫描电镜分析观察复合材料的物相组成及微观形貌。并测试复合材料的抗弯强度、断裂韧性及硬度。结果表明:两次球磨后的TiB2/ZrB2/SiC粉体粒度较小(2~4μm),且分布较均匀,几乎没有团聚现象。烧结后的复合功能材料中有(TixZry)B2固溶体相生成。当加入ZrB2的体积分数为30%时,生成的(TixZry)B2固溶体在复合材料中起到了很好的晶粒细化与界面融合作用,所以TZS30复合陶瓷材料比TZS0复合陶瓷材料的抗弯强度和断裂韧性分别提高了119.8%和98.9%。利用TiB2/ZrB2/SiC复合陶瓷材料在高温摩擦作用下与氧的化学反应,可以实现自润滑。     

盐津桥水库右坝肩下游岩体稳定与工程加固处理

盐津桥水库大坝上游220m为新建公路大桥，下游3km有一个国内有名的大型企业，因此大坝的安全尤为重要．盐津桥水库工程岩体边坡为顺层边坡，卸荷裂隙发育．根据裂隙及分布特征情况，采用三维刚体极限平衡法分析右坝肩下游在卸荷裂隙、软弱夹层或顺坡岩层、X节理下的岩体稳定性．由计算分析结果提出经济合理的边坡加固处理措施．     

Experimental investigation on the plasma morphology of ablative pulsed plasma thruster with tongue-shaped and flared electrodes

Ablative pulsed plasma thrusters(APPTs) are considered as an attractive propulsion option for station-keeping and drag makeup purposes for mass-and power-limited satellites. In order to understand the physical mechanism of APPTs, high-speed camera and optical emission spectroscopy are utilized to investigate the plasma characteristics including the spatial distribution and composition between the electrodes. The plume images and spectra at different times and positions are experimentally recorded, and the spatial distribution, composition, and trajectory of plasmas can be concluded through analyzing them. With the increase of the distance from the ablation surface, two clusters of plasmas near the anode and cathode meet downstream,and the species and density of plasmas tend to be uniform.     

Identification of heavy metal-contaminated Tegillarca granosa using laser-induced breakdown spectroscopy and linear regression for classification

Tegillarca granosa (T. granosa) is susceptible to heavy metals, which may pose a threat to consumer health. Thus, healthy and polluted T. granosa should be distinguished quickly. This study aimed to rapidly identify heavy metal pollution by using laser-induced breakdown spectroscopy (LIBS) coupled with linear regression classification (LRC). Five types of T. granosa were studied, namely, Cd-, Zn-, Pb-contaminated, mixed contaminated, and control samples. Threshold method was applied to extract the significant variables from LIBS spectra. Then, LRC was used to classify the different types of T. granosa. Other classification models and feature selection methods were used for comparison. LRC was the best model, achieving an accuracy of 90.67%. Results indicated that LIBS combined with LRC is effective and feasible for T. granosa heavy metal detection.     

Molecular dynamics simulations of the interaction between OH radicals in plasma with poly-β-1–6-N-acetylglucosamine

Cold atmospheric plasma shows a satisfactory ability to inactivate bacterial biofilms that are difficult to remove using conventional methods in some cases. However, the researches on the inactivation mechanism are not quite sufficient. Poly-β-1–6-N-acetylglucosamine (PNAG), which is one of the important components in some biofilms, was used as the research subject, and the related mechanism of action triggered by different concentrations of the OH in plasma was studied using reactive molecular dynamics simulations. The results showed that OH radicals could not only trigger the hydrogen abstraction reaction leading to cleavage of the PNAG molecular structure, but undergo an OH addition reaction with PNAG molecules. New reaction pathways appeared in the simulations as the OH concentration increased, but the reaction efficiency first increased and then decreased. The simulation study in this paper could, to some extent, help elucidate the microscopic mechanism of the interaction between OH radicals in plasma and bacterial biofilms at the atomic level.     

基于函数插值的柯氏质量流量计信号处理方法

对基于离散傅里叶变换(DFT)信号处理方式的柯氏质量流量计来说,影响其精度的关键问题是如何实现信号的整周期采样。提出了一种全新的方法,用采样率固定不变的采样数据,通过软件实时地确定信号的频率并且实现信号整周期重新采样。实验结果表明该方法在求取相位差时具有极高的精度。