高效液相色谱法分析茶叶中吡虫啉残留量

吡虫啉（Imidacloprid）中文通用名为咪蚜胶，属硝基亚甲基类内吸性低毒杀虫剂。其作用是选择性抑制昆虫神经系统中的烟酸乙酰胆碱脂酶受体，从而破坏昆虫的中枢神经的正常传导，使之神经麻痹后死亡，在农产品种植过程中用于防治刺吸式口器害虫。它对黑尾叶蝉、飞虱类、蚜虫类和蓟马类有优异的防效作用，效果优于噻嗪酮、醚菊酯、抗蚜威和杀螟丹等农药，因此，近年来被广泛用于茶叶生产上。     

瓜环与哌嗪衍生物主客体配合物的研究(英)

本文采用核磁共振技术研究瓜环与哌嗪衍生物主客体配合物的结构特征。¹H核磁共振谱证实八元瓜环能与一些哌嗪衍生物形成稳定的双客体主客体配合物,六元瓜环与一些哌嗪衍生物形成稳定的1∶1主客体配合物。而五、七元瓜环和哌嗪衍生物则未表现出明显地相互作用。形成的自组装主客体配合物得到质谱的进一步证实。     

手性氨基亚磺酰胺的合成及其对N-苯基酮亚胺不对称还原的催化作用

从N-保护的手性氨基醇出发,经氧化成醛后,与手性叔丁基亚磺酰胺发生缩合反应,再经一步还原胺化合成了一系列新型手性氨基亚磺酰胺有机小分子催化剂.将其应用于N-苯基酮亚胺的不对称硅氢化反应中,以中等收率和对映选择性获得了相应的N-苯基手性胺.     

加速溶剂萃取-凝胶渗透色谱净化-气相色谱快速分析动物源性食品中残留的多种有机磷农药

建立了动物源性食品猪肉、牛肉、鸡肉及鱼肉中36种有机磷农药残留的快速分析方法。以乙腈作为溶剂,对试样采用加速溶剂萃取仪萃取,自动凝胶渗透色谱仪净化预处理,N-丙基乙二胺(PSA)填料再净化,毛细管气相色谱法分离,火焰光度检测器(磷型)检测,内标法定量。该方法分离效果良好,重现性好,灵敏度、精密度高,杂质干扰少。36种有机磷农药的检测限(LOD)为0.0012 mg/kg(乙拌磷)～0.014 mg/kg(吡唑硫磷),定量限(LOQ)为0.004 mg/kg(乙拌磷)～0.047 mg/kg(吡唑硫磷)。当试样中有机磷农药的添加浓度分别为0.05,0.1,0.2 mg/kg时,回收率为58.2%～106.3%。方法的最低检测限和添加回收率均符合农药残留分析的要求。     

醋酸酯淀粉/聚乙烯醇共混膜形态结构与性能

以溶液共混法制备了醋酸酯淀粉(SA)/聚乙烯醇(PVA)共混膜,通过扫描电镜(SEM)观测其表面形貌、X射线衍射仪(XRD)表征其结构、Zwick强力仪测试其力学性能.结果表明,醋酸酯化变性及SA与PVA之间的共混比对共混膜的形态结构及力学性能均有影响.随着淀粉醋酸酯化变性程度的增大,共混膜的断裂伸长率增大;当变性取代度达到0.035之后,断裂强度明显增大.增加SA的质量分数,共混膜的断裂伸长率减小,断裂强度先降低后增大;当共混比为50∶50时,断裂强度最小.     

（mg＋k,mf—k）—图中正交于r个不相交子图的边不变的（g,f）—因子

设m,k和r为正整数,且使l≤k＜m.设G是一个具有顶点集合V(G)和边集合E(G)的图,并设g和f是定义在V(G)上的使对每个x∈V(G)有r≤g(x)≤f(x)的整数值函数.设H1,H2,…,Hr是G的r个顶点不相交的子图且|E(Hi)|=k,1≤i≤r.本文证明了每个(mg+k,mf-k)-图有k个边不相交的(g,f)-因子正交于Hi,1≤i≤r.     

〈111〉晶向冲击加载下单晶铜中纳米孔洞增长的早期动力学行为

利用分子动力学方法模拟计算了单晶铜中纳米孔洞在沿〈111〉晶向冲击加载下增长的早期过程.测量发现不同加载强度下等效孔洞半径随时间近似成线性变化.观测到单孔洞增长的两种位错生长机理：加载强度较低时，只在沿着冲击加载方向的孔洞顶点附近区域有位错的成核和运动；而随着加载强度超过一定阈值，在沿冲击加载和其垂直方向的孔洞顶点区域都观察到位错的成核和运动.在前一种机理作用下，孔洞只沿加载方向增长；在后一种机理作用下，孔洞同时沿加载和垂直于加载方向增长.分析孔洞表面原子的位移历史，发现沿加载及与其垂直方向的孔洞顶点沿径向的速度基本恒定，由此提出了一个孔洞生长模型，可以解释孔洞增长的线性生长规律. 关键词： 纳米孔洞 分子动力学 冲击加载 位错     

The degradation mechanism of an AlGaN/GaN high electron mobility transistor under step-stress

Step-stress experiments are performed in this paper to investigate the degradation mechanism of an AlGaN/GaN high electron mobility transistor(HEMT).It is found that the stress current shows a recoverable decrease during each voltage step and there is a critical voltage beyond which the stress current starts to increase sharply in our experiments.We postulate that defects may be randomly induced within the AlGaN barrier by the high electric field during each voltage step.But once the critical voltage is reached,the trap concentration will increase sharply due to the inverse piezoelectric effect.A leakage path may be introduced by excessive defect,and this may result in the permanent degradation of the AlGaN/GaN HEMT.     

Efficient and stable wireless power transfer based on the non-Hermitian physics

As one of the most attractive non-radiative power transfer mechanisms without cables,efficient magnetic resonance wireless power transfer(WPT)in the near field has been extensively developed in recent years,and promoted a variety of practical applications,such as mobile phones,medical implant devices and electric vehicles.However,the physical mechanism behind some key limitations of the resonance WPT,such as frequency splitting and size-dependent efficiency,is not very clear under the widely used circuit model.Here,we review the recently developed efficient and stable resonance WPT based on non-Hermitian physics,which starts from a completely different avenue(utilizing loss and gain)to introduce novel functionalities to the resonance WPT.From the perspective of non-Hermitian photonics,the coherent and incoherent effects compete and coexist in the WPT system,and the weak stable of energy transfer mainly comes from the broken phase associated with the phase transition of parity-time symmetry.Based on this basic physical framework,some optimization schemes are proposed,including using nonlinear effect,using bound states in the continuum,or resorting to the system with high-order parity-time symmetry.Moreover,the combination of non-Hermitian physics and topological photonics in multi-coil system also provides a versatile platform for long-range robust WPT with topological protection.Therefore,the non-Hermitian physics can not only exactly predict the main results of current WPT systems,but also provide new ways to solve the difficulties of previous designs.     

接枝淀粉浆料氧化还原接枝引发剂的评价

以丙烯酸(AA)及丙烯酸甲酯(MA)为接枝模型单体,以接枝率、接枝效率、单体转化率、黏度、黏度热稳定性和黏附性能为评价指标,研究了Ce(NH4)2(NO3)6,FeSO4/H2O2,KMnO4/C6H8O7,K2S2O8/Na2S2O3,(NH4)2S2O8/NaHSO35种引发体系对淀粉的接枝引发作用,评价了它们作为接枝淀粉浆料引发剂的优劣,为进一步改善接枝淀粉浆料的使用性能奠定基础,为工业化生产提供参考和依据.研究结果表明,(NH4)2S2O8/NaHSO3和FeSO4/H2O2是性价比较高的引发剂,可以作为接枝淀粉浆料的引发剂.