Determination of phenylenediamine isomers in hair dyes by coal cinders micro-column extraction and MEKC

A new micellar electrokinetic chromatography (MEKC) method using beta-cyclodextrins (β-CDs) and 1-butyl-3-methylimidazolium hexafluorophosphates (ionic liquids) as additives was successfully developed for determination of para-, meta-, and ortho-phenylenediamines isomers (p-P, m-P, and o-P) in hair dyes. To improve the sensitivity of the MEKC-UV, a simple and cheap flow injection (FI) technique using a micro-column packed with coal cinders (the by-products from combustion in a boiler) as solid-phase extractant was also investigated. In the presence of 20 mmol L(-1) phosphates at pH 5.5, addition of 12 mmol L(-1) ionic liquids and 8 mmol L(-1) β-CDs greatly improved the separation efficiency. The three analytes could be quantitatively adsorbed by coal cinders, and desorbed readily with 0.15 mL of 0.01 mol L(-1) NaOH. Under the optimum conditions, an enrichment factor (EF) of 33.3 was obtained, and determination limits of p-P, m-P, and o-P were 1.97?×?10(-7), 0.99?×?10(-7), and 0.61?×?10(-7) mol L(-1), respectively. The adsorption capacities of the coal cinders micro-column for p-P, m-P, and o-P were all 1.20 mg g(-1). The presented procedure was successfully applied to the determination of p-P, m-P, and o-P in hair dyes with satisfactory results.     

关于一个脉冲用药的HIV免疫模型的研究

对一个脉冲用药的HIV免疫模型进行研究,发现在用药间隔足够小时,预防抗化剂的脉冲使用通过使T细胞水平无限接近于未被感染的免疫水平来保持个体的免疫功能,并且文中进一步给出这个合适的用药间隔估计.这对指导AIDS治疗临床实践具有参考意义.     

一个海洋噬菌体感染模型的分析

对一个海洋病毒感染模型进行研究,分析其动力学行为,研究系统平衡点的存在性,稳定性及分支的产生.这对海洋生态研究具有一定意义.     

Health impact and safety of engineered nanomaterials

Many engineered nanomaterials (NMs) are being synthesized and explored for potential use in consumer and medical products. Already, nanoparticles (NPs) of titanium dioxide (TiO(2)), zinc oxide (ZnO), silver (Ag) and other metals or their oxides are present in commercial products such as sunscreens, cosmetics, wound dressings, surgical tools, detergents, automotive paints and tires. More recent and advanced FDA-approved use of NMs includes quantum dots (QDs) in live cell imaging, zirconium oxides in bone replacement and prosthetic devices and nanocarriers in drug delivery. The benefits from nanotechnology are aplenty, comprising antimicrobial activities, scratch- and water-resistance, long-lasting shine, improved processor speeds and better display resolution, to name a few. While developers of these products often focus on the exciting beneficial aspects of their products, safety and toxicity issues are often not discussed in detail. Long-term effects such as chronic exposure and environmental pollution are even less documented. Along with widespread manufacture and use of NMs, concerns for occupational hazards, proper handling, disposal, storage, shipping and clean up are expected to rise. This review focus on the possible biological impact of engineered NPs, serving as a reminder that nanomaterials can become a double-edged sword if not properly handled.     

我国汽车产业竞争力区域差异的实证研究

近年来,随着汽车产业对我国经济增长贡献日渐提高,各省市纷纷将汽车产业定位为支柱产业来发展。本文基于汽车产业竞争力分析框架,根据我国各省市、自治区2001-2009年的统计数据,从产业规模、技术能力、经营效率和成长能力四个方面,实证分析汽车产业竞争力区域差异。研究发现,我国汽车产业竞争力区域差距较大,在汽车产业水平领先的地区出现明显两极分化,而一些汽车产业水平落后的地区却具备较强的成长能力,其结论对推动中国汽车产业的发展具有重要的借鉴意义。     

广义活动网络ETI支付进度计划问题的研究

优化ETI支付进度安排是消除承包商和业主由于进度安排原因而产生经济纠纷,实现双赢的最有效方法.本文分析了活动间广义时序关系的类型,建立了广义时序关系下活动间的约束关系;在考虑承包商和业主双方联合收益要求的基础上,提出了双方的净现值按同比例减小的折衷原则,构建了广义活动网络在ETI支付方式下的支付进度计划模型;最后通过一个算例进行了分析,验证表明该优化模型具有较好的有效性和实用性.     

气压对压力容器前壁超高速撞击损伤的影响

充气压力容器在超高速撞击下的典型损伤包括穿孔及其边缘的裂纹失稳破坏,会导致气体泄漏或爆炸,内压对容器前壁损伤的影响仍不明确。以不同内压的球形铝合金充气压力容器为研究对象,开展了球形铝合金弹丸超高速撞击实验和数值模拟计算,分析了内充气体压强对前壁穿孔形貌特征、穿孔直径、孔边环向应力等的影响规律和影响机理,讨论了气体冲击波的传播行为及影响前壁穿孔边缘裂纹失稳破坏的机制。结果表明:前壁穿孔边缘内翻边形貌与内压相关,内压越高,弯折程度越轻;穿孔直径与内充气体压强正相关,但气体对孔径的影响远小于容器壁厚及撞击速度的影响;穿孔边缘使裂纹失稳破坏的环向拉应力不仅受到后壁反射冲击波的影响,也与容器壁内应力波的传播有关,与内压成正比。     

具有工作故障及有限容量的MAP/M/1排队系统性能分析

为了拓展随机排队理论,在具有工作故障的MAP/M/1排队的基础上,引入有限容量策略建立起一个新的排队模型.通过Uniformization Technique将连续时间排队模型转化成对应的离散时间排队模型,运用矩阵几何组合解给出系统中的顾客数量和服务器状态的联合稳态概率表达式,并给出基于稳态概率的性能指标.最后通过一些数值例子展示参数对性能指标的影响.     

高光谱成像的机采籽棉杂质分类检测

机采籽棉杂质分类检测为调整棉花清理机械加工参数和工序提供参考依据,对提升皮棉品质具有重要意义。但由于籽棉棉层分布不均匀,使得图像检测难度增大,使用传统的检测方法无法有效检测各类杂质。采用高光谱成像方法对机采籽棉中的棉叶、棉枝、地膜和铃壳（内外）五种杂质进行分类判别检测。首先采集120个机采籽棉样本的高光谱图像,选取感兴趣区域获取平均光谱曲线。发现由于物质构成的差异,不同杂质体现出不同的吸收和反射特性,不同种类物质之间的光谱差异大于同类物质。对提取的平均光谱曲线进行主成分分析（PCA）,结果显示棉花、残膜和铃壳外与其他三类相比,有较好的聚集性和可分性,但是棉叶、铃壳内和棉枝三类相互叠加在一起,空间分布存在严重交叉重叠。以提取的平均光谱曲线为训练样本,选择线性判别分析（LDA）、支持向量机（SVM）和神经网络（ANN）三种分类判别算法,对算法参数进行寻优,并建立机采籽棉杂质分类判别模型。其中,经过LDA模型降维后的样本空间较PCA表现出了更好的聚集性和可分性,采用正则化防止过拟合,得到训练集准确率为86.4%,测试集准确率为86.2%;SVM模型的参数寻优结果为C=105,g=0.1,其训练集准确率为83.42%,测试集准确率为83.40%;ANN模型参数寻优得到隐含层数和神经元个数分别为2和17,训练集准确率为82.9%,测试集准确率为81.8%。对三种模型的分类效果和检测用时进行比较,LDA模型结果最优。通过对高光谱图像进行像素等级分类判别,结果显示棉花识别效果较好,植物性杂质都被有效检测,但是地膜和棉花存在误识别,分类效果与杂质光谱的分类判别模型结果一致。因此,采用高光谱成像技术可以快速、无损的检测和识别籽棉杂质,为棉花加工装备提供反馈参数,对棉花加工机械化和智能化有重要意义。