氢氧化钡处理-分散液液微萃取结合气相色谱-串联质谱法测定肉制品中9种N-亚硝胺

目的 建立氢氧化钡碱溶液-分散液液微萃取结合气相色谱-串联质谱法(gaschromatography-tandem massspectrometry,GC-MS/MS)同时测定肉制品中9种N-亚硝胺类化合物的分析方法。方法 肉制品样品在80℃水浴中经氢氧化钡碱溶液皂化,去除油脂干扰,进一步将N-亚硝胺提取到水溶液中,再加入甲醇(分散剂)和二氯甲烷(萃取剂)进行高效萃取富集,在多反应监测模式下分析,稳定同位素内标法定量。对影响萃取效率的因素进行考察,如样品提取步骤中的皂化条件,无机盐、萃取剂和分散剂的种类及体积等。通过优化色谱、质谱参数和前处理条件,获得最佳检测结果。结果 除了N-亚硝基二甲胺(N-nitrosodimethylamine, NDMA)的线性范围为2.5～50.0 ng,其他8种N-亚硝胺类化合物在1.0～50.0 ng范围内线性关系良好, 9种N-亚硝胺类化合物的相关系数(r2)范围为0.9954～0.9999,方法检出限和定量限分别为0.1～0.2μg/kg和0.2～0.5μg/kg。在火腿、五香鸡肉和牛肉样品中分别进行0.5、5.0μg/kg浓度水平的加标实验,所有...     

Synthesis of titania microspheres with hierarchical structures and high photocatalytic activity by using nonanoic acid as the structure-directing agent

The titania, as the heterogeneous photocatalyst, has attracted much attention in attempts to eliminate pollutants, especially organic compounds in water and air. In this study, the titania microspheres with hierarchical structures were prepared by a combined sol–gel and solvothermal method. The X-ray powder diffraction (XRD) result indicated that the synthesized titania microspheres were of anatase phase. Field-emission scanning electron microscope (FESEM) and high-resolution transmission electron microscope (HRTEM) showed that the microspheres with well-dispersity had an average diameter of 651 nm and were composed of nanoparticles with about 20 nm in diameter. The Brunauer–Emmett–Teller (BET) results showed that the microspheres possessed high surface areas and lots of mesopores. Further study indicated that the synthesized titania microspheres exhibited high photocatalytic activity and had an important advantage over the commercial P25.     

Sorption of nitrate onto amine-crosslinked wheat straw: characteristics, column sorption and desorption properties

The nitrate removal process was evaluated using a fixed-bed column packed with amine-crosslinked wheat straw (AC-WS). Column sorption and desorption characteristics of nitrate were studied extensively. Solid-state (13)C NMR and zeta potential analysis validated the existence of crosslinked amine groups in AC-WS. Raman shift of the nitrate peaks suggested the electrostatic attraction between the adsorbed ions and positively charged amine sites. The column sorption capacity (q(ed)) of the AC-WS for nitrate was 87.27 mg g(-1) in comparison with the raw WS of 0.57 mg g(-1). Nitrate sorption in column was affected by bed height, influent nitrate concentration, flow rate and pH, and of all these, influent pH demonstrated an essential effect on the performance of the column. In addition, desorption and dynamic elution tests were repeated for several cycles, with high desorption rate and slight losses in its initial column sorption capacity.     

等离子喷涂中雷诺数对熔滴扁平化行为的影响

采用狭缝法收集不同工艺条件(雷诺数)下的氧化钇部分稳定的二氧化锆(YSZ)扁平粒子, 采用扫描电子显微镜(SEM)及三维激光显微镜观察形貌, 同时采用Fluent流体力学软件模拟不同雷诺数下YSZ熔滴的铺展和凝固过程, 研究雷诺数对扁平粒子形貌的影响规律。实验及计算结果表明: 当欧氏数大于0.2时, 雷诺数对YSZ熔滴的扁平化行为具有重要的影响作用, 熔滴飞溅的临界雷诺数为450±20, 即当雷诺数小于450±20时, 熔滴呈圆盘状且不发生飞溅, 反之熔滴发生飞溅。对于粒径相同的YSZ熔滴, 超音速等离子喷涂(SAPS)获得的熔滴扁平率约为普通等离子喷涂(APS)工艺的1.3倍。     

超声波检测中的小波降噪

论文介绍了小波分析在检测信号处理中的应用,并通过对超声波的传播进行分析得到超声波信号的噪声产生原因,构建了含噪回波信号的数学模型。对原始信号采用小波分解重构降噪、硬阈值降噪、软阈值降噪三种方法进行信号处理,并对三种方法进行比较。     

海娇颜片中原花青素含量快速测定方法优化

目的优化快速测定海娇颜片中原花青素含量的分析方法。方法通过加标回收率法发现采用铁盐催化比色法测定海娇颜片中原花青素时的干扰成分,并分别采用大孔树脂柱及乙醇沉淀-离心2种方法对样品进行前净化处理。结果发现海娇颜片中鱼胶原蛋白肽对原花青素的测定存在较大干扰,优化前测得原花青素含量为1.22%,经大孔树脂柱净化后测得其含量为2.15%,而经乙醇沉淀-离心净化后测定其含量为3.11%,接近理论值。结论乙醇沉淀-离心法能显著去除干扰成分,提高原花青素含量测定的准确度,是较优的样品预处理方法。该研究可为相关产品中原花青素含量快速测定方案的制定提供参考依据。     

农药核酸适配体筛选及应用的研究进展

核酸适配体是通过指数富集的配体系统进化(systematic evolution of ligands by exponential enrichment,SELEX)技术在体外筛选到的单链寡核苷酸,与靶标具有高亲和力和特异性,且稳定性好,易于合成和修饰,被认为是生物传感器的理想识别元件之一,在农药残留快速检测应用中表...     

不同母乳低聚糖对肠道LS174T杯状细胞黏蛋白分泌相关基因表达的影响

目的 分析不同母乳低聚糖对肠道LS174T杯状细胞黏蛋白分泌相关基因表达的影响。方法 以人肠道LS174T细胞为研究对象,将2’-岩藻糖基乳糖(2’-fucosyllactose,2’-FL)、3’-唾液酸乳糖(3’-sialyllactose,3’-SL)和低聚半乳糖(galactooligosaccharide, GOS) 3种低聚糖和乳糖对细胞的作用时间分成24 h组和48 h组,分别在细胞稳态和细胞炎症状态下,以黏蛋白2(mucin2,MUC2)及其相关基因[三叶因子-3(trefoilfactor3,TFF3)、抵抗素样蛋白B(recombinantresistinlikebeta,RETNLB)、碳水化合物磺基转移酶5(carbohydrate sulfotransferase 5, CHST5)、半乳糖-3-O-磺基转移酶2 (galactose-3-O-sulfotransferase 2, GAL3ST2)]的表达水平为评价指标,通过实时荧光定量多聚核苷酸链式反应(realtime-quantitativepolymerasechainreaction,RT-qPCR...     

基于区块链技术的查询索引认证方法

为了实时快捷地在视频流上生成模式索引,提出了基于区块链的索引认证方案,用于面向事件的实时监控视频查询.通过边缘节点和雾节点之间的加密安全信道来保护索引数据,以提升智能监控系统的安全性.首先,通过在嵌入式边缘设备上执行检测和跟踪任务,面向事件的监控服务通过处理输入帧来提取特征信息;然后,实时索引服务为每帧生成唯一性索引,以防止对图像的恶意修改;最后,将帧索引输入区块链网络,并通过基于去中心化智能合约的认证机制进行验证.实验结果证明了本文方案的可行性和有效性.其总开销非常低,适用于实时监控视频查询的应用.     

卷积神经网络下的高分二号卫星影像道路提取

本文针对深度神经网络对高分二号遥感影像道路提取时细节信息丢失较多、道路周围环境考虑不充分等情况,在已有的研究成果上,提出一种基于全卷积神经网络遥感影像道路提取的改进方案.方案创新研究了全卷积神经网络的算法原理,将预调色后的高分二号影像按一定尺寸分幅输出,将输出图像及标签对应输入于以全卷积神经网络为基础的改进网络,通过结合残差单元以及增加网络层数得到识别精度较高的道路提取图像.实验表明,该方法在同一样本中对高分二号卫星影像道路提取的效果有所提升,道路的完整性和准确性有所提高.