Fabrication and morphology of spongelike polymer material based on cross-linked sulfonated polystyrene particles

A novel spongelike polymer material has been fabricated by γ-ray induced polymerization of methylmethacrylate (MMA) in an emulsion containing cross-linked sulfonated polystyrene (CSP) particles. Scanning electron microscopy (SEM) images reveal that the spongelike structure is made up of interlinked nanosized PMMA particles with micrometer-sized CSP-PMMA particles embedded inside. The nitrogen adsorption isotherm discloses that the spongelike material has a high specific surface area of 29 m(2)/g and a narrow pore size distribution of 60-120 nm. The formation mechanism is discussed in this paper, which indicates that the key steps to form the spongelike material include a Pickering emulsion stabilized by the CSP particles, followed by the swelling process of MMA into these particles. This approach offers a more convenient alternative to prepare polymeric spongelike material without any etching procedure.     

A novel approach for preparation of “cage-like” multihollow polymer microspheres through sulfonated polystyrene particles

A new and effective process has been developed for fabrication of novel cage-like multihollow polymer particles by using sulfonated polystyrene (SP) particles as the templates, with heptane as the phase separation agent, in an ethanol/water medium. The ratio of water/ethanol and the heating temperature play important roles in the formation of these multihollow particles. It was found that the cage-like polymer particles could be obtained when the ratio of ethanol/water is 5:5 (w/w), with a temperature above 50?°C. After a detailed study, the formation mechanism was proposed based on an SP swollen (ethanol and heptane penetrating process) and phase separation process. This new method for fabricating the cage-like multihollow polymer particles has a great meaning not only on confirming the formation mechanism, but also on providing an effective way to prepare the special hollow core/porous shell polymer particles, which could have wide range of potential applications, such as catalysts, sensors, and drug release.     

Langford系统Hopf分岔极限环幅值控制

系统地研究了Langford 系统Hopf分岔极限环幅值非线性反馈控制问题.根据中心流形定理和规范型降维理论, 推导含控制增益项的非线性曲率系数控制公式和幅值近似解,通过数值仿真验证并绘制极限环幅控关系曲线. 所推导的控制公式为Langford 系统极限环幅值控制提供了方便有效的控制方法.     

利用ICCD定位宇宙线来测量探测器时间分辨的方法研究

本研究采用双层150 mm×150 mm闪烁条阵列定位宇宙线的入射和出射位置. 阵列信号光使用波移光纤吸收传输,在ICCD相机前插入前置像增强器,使信号光延迟大于200 ns, 使ICCD可以由外部高速触发信号控制,有效记录随机触发事例.该宇宙线定位系统可以同时多点密集测量 通用探测器测试平台的时间分辨和闪烁光的渡越时间.该新方法与传统时间分辨测量方法相比提高了30倍以上 的效率.实验结果显示:时间探测器的时间分辨好于200 ps,满足通用探测器测试平台的设计要求.     

亚波长金属线阵中一维时间反演电磁波的聚焦机理研究

基于周期金属线阵的等效电介质模型, 并使用传输线理论方法, 得到了金属线阵中时间反演电磁波的解析表达式. 接着, 在等效电介质模型的适用范围内, 讨论了金属线半径、金属线阵周期、金属线阵周期数对时间反演电磁波聚焦的影响. 从而在理论上证实, 这种结构可以实现远场时间反演电磁波聚焦, 同时, 也为时间反演技术提供了工程参考.     

Zno纳米粒子在PS中空微反应器中的合成与光学性能

通过种子乳液聚合合成核壳结构的聚甲基丙烯酸甲酯/聚苯乙烯(PMMA/PS)复合微球,通过酸碱溶胀法进一步制备出次微米级的PS中空微球. 将此中空微球作为微反应器,使在ZnO纳米粒子前驱体溶液中溶胀, 最终ZnO纳米粒子在PS中空微球中原位生成. 实验表明, 组成ZnO纳米粒子前驱体溶液的两种组 分(CH₃COO)₂Zn和LiOH的滴加顺序不同对最终生成的ZnO纳米粒子的尺寸和负载效率有很大的影响,但并不改变ZnO纳米粒子的晶型. 复合物的光致发光和UV-Vis吸     

用于XRF分析的U-Nb合金试样制备方法

用X射线荧光光谱法(XRF)测量U-Nb合金样品时,其试样制备至关重要。本文用XRF测量U-Nb合金试样的制备方法:首先用HNO3+HF溶样,然后加入柠檬酸溶液,依次经过加热、除酸、络合、定容等过程,最后定量移取试液于滤纸片上,在红外灯下烤干,即制成试样片。该方法制备的U-Nb合金试样片具有平整、不变形、易于封装、可长期存放等特点。     

银离子络合法提取核桃油中不饱和脂肪酸

对皂化后的核桃油进行酸化获得混合脂肪酸,再对其进行甲酯化得混合脂肪酸甲酯,采用硝酸银络合萃取法提取混合脂肪酸甲酯中的不饱和脂肪酸甲酯。实验结果表明,以1mol/L氢氧化钾-无水乙醇溶液进行皂化,40%甲醇水溶液溶剂,硝酸银浓度为2mol/L,0℃的条件下络合萃取2h效果最佳,不饱和脂肪酸含量由72.3%增加到96.3%。     

Characteristic ion clusters as determinants for the identification of pyrrolizidine alkaloid N-oxides in pyrrolizidine alkaloid-containing natural products using HPLC-MS analysis

Pyrrolizidine alkaloid (PA)-containing plants are widely distributed in the world. PAs are hepatotoxic, affecting livestock and humans. PA N-oxides are often present together with PAs in plants and also exhibit hepatotoxicity but with less potency. HPLC-MS is generally used to analyze PA-containing herbs, although PA references are unavailable in most cases. However, to date, without reference standards, HPLC-MS methodology cannot distinguish PA N-oxides from PAs because they both produce the same characteristic ions in mass spectra. In the present study, the mass spectra of 10 PA N-oxides and the corresponding PAs were systemically investigated using HPLC-MS to define the characteristic mass fragment ions specific to PAs and PA N-oxides. Mass spectra of toxic retronecine-type PA N-oxides exhibited two characteristic ion clusters at m/z 118-120 and 136-138. These ion clusters were produced by three unique fragmentation pathways of PA N-oxides and were not found in their corresponding PAs. Similarly, the nontoxic platynecine-type PA N-oxides also fragmented via three similar pathways to form two characteristic ion clusters at m/z 120-122 and 138-140. Further application of using these characteristic ion clusters allowed successful and rapid identification of PAs and PA N-oxides in two PA-containing herbal plants. Our results demonstrated, for the first time, that these characteristic ion clusters are unique determinants to discriminate PA N-oxides from PAs even without the availability of reference samples. Our findings provide a novel and specific method to differentiate PA N-oxides from PAs in PA-containing natural products, which is crucial for the assessment of their intoxication.     

An efficient three-component, one-pot synthesis of 2-alkylthio-4-amino-5-cyano-6-aryl(alkyl)pyrimidines in water

A convenient and practical method for the synthesis of 2-alkylthio-4-amino-5-cyano-6-aryl(alkyl)pyrimidines has been developed via a three-component, one-pot reaction from aldehydes, malononitrile and S-alkylisothiouronium salts in water at room temperature. A series of polysubstituted pyrimidines were prepared by this method in moderate to excellent yields. In addition, two kinds of pyrimidine-fused heterocyclic derivatives with potential pharmacological activity were constructed from our 2-alkylthio-4-amino-5-cyano-6-arylpyrimidines.