Separation and determination of diversiform phytosterols in food materials using supercritical carbon dioxide extraction and ultraperformance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry

This paper presents at first time that the ultra-performance™ liquid chromatographic atmospheric pressure chemical ionization mass spectrometer (UPLC-APCI-MS) was used as an efficient method for the identification and quantification of diversiform phytosterols in food materials. The sample preparation consisted of extraction by supercritical carbon dioxide fluid extraction (SCE) and saponification by refluxing with ethanolic KOH, and then the non-saponificable fraction was extracted with petroleum ether. This fraction was subjected to solid phase extraction (SPE) on silica gel cartridge and then the sterols were eluted with hexane-ethyl acetate. Sterols were separated on an Acquity UPLC™ BEH C18 column (100 mm × 1.0 mm, 1.7 μm particle size) with a gradient of methanol/water (1% acetonitrile) at a flow of 0.1 mL min⁻¹. The determination was performed in selective ion monitoring mode. The quality parameter of the developed method was established using 6-ketocholestanol as internal standard. Limits of quantification (LOQ) were 0.1754, 0.0341, 0.0500, 0.0205, 0.0225, 0.3674, 0.0241, 0.0272, 0.0076 μg L⁻¹ and 0.1525 μg mL⁻¹ for 6-ketocholestanol, desmosterol, ergosterol, cholesterol, lanosterol, cholestanol, campesterol, stigmasterol, β-sitosterol, and stigmastanol, respectively. The intra- and inter-day determination precision for the 10 phytosterols were less than 5 and 6% in relative standard deviations, and their recoveries were located in the range of 94-107%. The developed approach has been applied successfully for efficient determination of diversiform phytosterols in food materials, including corn, sesame, oat and peanut.     

基于DNA链置换反应的新型固定化酶反应器制备及应用

建立了一种新型的酶固定化方法,采用DNA链置换反应成功地在单链DNA标记的磁性纳米粒子上实现了酶的链置换无损更替。该技术可实现目标酶的再利用,节约了生产成本。制备的固定化胰蛋白酶微反应器具有较好的重复利用性和高酶切效率,重复使用10次后仍可保持原酶活性的86%;利用链置换反应制备的MNPs@DNATrypsin酶切马心肌红蛋白5 min后,即可获得95%±0%(n=3)的氨基酸序列覆盖率,远超过相同条件下自由酶酶切12 h的结果。实验表明,发展的固定化酶技术具有高磁响应性,便于从反应体系中回收固定化酶和重复使用,同时此技术可显著提高酶活性,因此可用于固定各种重要的酶,同时可将其广泛应用于各种酶促反应中。     

A glassy carbon electrode modified with FeS nanosheets as a highly sensitive amperometric sensor for hydrogen peroxide

Iron sulfides with different atomic ratios were synthesized by a hydrothermal method and used to modify a glassy carbon electrode. The various sulfides were compared to each other for their amperometric response to H₂O₂. It is found that FeS is the most adequate material. Operated in 0.1 M NaOH solution at 0.4 V (vs. Ag/AgCl), the sensor based on FeS displays a linear response that extends from 0.50 μM to 20.5 mM of H₂O₂, with a sensitivity of 36.4 μA mM^?1 cm^?2 and a detection limit of 0.15 μM (at an S/N ratio of 3). The sensor is selective, stable and reproducible.

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Graphical abstract Schematic of the synthesis of pomegranate flower-like FeS by a hydrothermal route using ferric chloride and thiourea (SC(NH₂)₂) as the precursors, and ethanolamine (EA) as the structure-guiding auxiliary agent. A glassy carbon electrode (GCE) modified with this material allows for amperometric sensing of hydrogen peroxide in 0.1 M NaOH solution with a 0.15 μM detection limit. 

     

Impacts of nanoscale zero-valent iron on nitrite accumulation performance of nitritation granular sludges with different spatial morphologies and its biosorption behavior

Research on Chemical Intermediates - To explore the potential impacts of nanoscale zero-valent iron (nZVI) particles on nitrite accumulation performance of nitritation granular sludge (NGS), two...     

基于纹理特征的小麦锈病动态模拟方法

病害仿真是农业信息化的重要研究内容之一,通过模拟病害发生过程,可方便直观有效地宣传作物病害有关知识。病害模拟在教学、影视及游戏等领域也有重大应用价值。为实现作物病害过程模拟,以小麦为研究对象,在温度与湿度变化环境下,对小麦条锈病、叶锈病、秆锈病3种锈病类型进行基于纹理特征的动态仿真模拟。用噪声模拟分布在小麦茎叶上的孢子堆,通过调整噪声属性模拟不同的锈病类型,从而达到逼真的模拟效果;通过改变遮罩贴图中红绿蓝（RGB）3种颜色分量的分布,指定模拟发病位置,区分小麦锈病的发病类型;通过着色器调整指定位置作物模型表面贴图,以径向为扩散路径,完成植株从完好到完全发病的可视化过程。该方法模拟效果较好,具有一定的研究意义与应用价值,可为其他作物的多病害模拟提供参考。     

火焰原子吸收光谱法测定冬枣中的微量元素

用火焰原子吸收光谱法测定了冬枣中钾、钠、钙、镁、铁、锰、铜和锌的含量。结果表明,该法的加标回收率为96.7%～102.8%,RSD≤3.06%。该法操作简单,结果准确,为冬枣资源的进一步开发利用和栽培技术的改进提供了参考依据。     

基于PSD的激光位移传感器位置补偿

针对激光位移传感器在检测截面距离时受到同步电机震动影响,产生随机误差的问题,运用PSD光电位移传感器及树莓派对误差数据进行采集.以实验室的身管设备为例,用python、matlab等软件进行曲线拟合,阐述了身管数据误差进行采集、分析处理及曲线拟合的基本流程,探讨了PSD在位置误差补偿方面的应用.基于激光位移传感器对身管...     

Efficient rate-distortion optimal packetization of embedded bitstreams into independent source packets

This paper addresses the rate-distortion (R-D) optimal packetization (RDOP) of embedded bitstreams into independent source packets, in order to limit error propagation in transmission of images over packet noisy channels. The input embedded stream is assumed to be an interleaving of K independently decodable basic streams. To form independent source packets, the set of basic streams is partitioned into N groups. The streams within each group are then interleaved to generate a source packet. Error/erasure protection may be further applied along/across source packets, to produce the channel packets to be transmitted. The RDOP problem previously formulated by Wu et at. has the goal of finding the partitioning that minimizes the distortion when all source packets are decoded. We extend the problem formulation such that to also include the minimization of the expected distortion for general transmission scenarios that may apply uneven erasure/ error protection. Further, we show that the dynamic programming (DP) algorithm of Wu et al. can be extended to solve the general RDOP problem. The main contribution of this paper is a fast divide-and-conquer algorithm (D&C) to find the globally optimal solution, under the assumption that all basic streams have convex R-D curves. Instrumental in obtaining the fast solution is our result which proves that the problem can be formulated as a series of matrix search problems in totally monotone matrices. The proposed D&C reduces the running time from O(K(2)LN) where L is the size of each packet achieved by the DP solution to O(NKL log K). Experiments on SPIHT coded images demonstrate that the speedup is significant in practice.     

纤维素键合手性固定相拆分6种萘满酮衍生物对映体

使用Chiralpak IC（纤维素-三（3,5-二氯苯基氨基甲酸酯）共价键合硅胶）手性柱,建立了采用手性固定相高效液相色谱拆分6种 α -芳基萘满酮类衍生物对映体的方法。考察了流动相中有机改性剂的种类和比例、柱温和流速对对映体分离的影响。结果显示6种化合物在异丙醇为改性剂的条件下均可获得较高的对映体分离度。热力学研究表明6种化合物对映体的手性拆分过程均受焓驱动影响,且低温有利于对映体分离。最终推荐分离化合物Ⅰ对映体的流动相是正己烷-异丙醇（90：10,v/v）;分离化合物Ⅱ、Ⅲ、Ⅳ对映体的流动相是正己烷-异丙醇（99：1,v/v）;分离化合物Ⅴ对映体的流动相是正己烷-异丙醇（85：15,v/v）;分离化合物Ⅵ对映体的流动相是正己烷-异丙醇（80：20,v/v）。柱温为25℃,流速为1.0 mL/min。6种化合物对映体均可在Chiralpak IC手性固定相上得到完全分离,证明该色谱柱对6种化合物具有较高的对映体选择性。