亚临界水萃取及气相色谱-串联质谱法检测红茶中多种农药残留

建立了亚临界水萃取及气相色谱-串联质谱(GC-MS/MS)检测红茶中21种有机氯和拟除虫菊酯农药残留的方法。在萃取压力为5 MPa条件下,样品经150 ℃的亚临界水提取15 min后,将目标物转移至丙酮-正己烷(1:1, v/v)中,经ENVI-Carb固相萃取净化小柱净化,DB-5毛细管气相色谱柱分离,在多反应监测(MRM)模式下进行MS/MS检测,基质匹配溶液内标法定量。各目标物在5.0～320.0 μg/L范围内线性关系良好,相关系数均大于0.99,其定量限(信噪比(S/N)＞10)为50 ng/g,检出限(S/N＞3)为10 ng/g。茶叶基质中添加50、100和200 ng/g的标准品时,21种农药的回收率为70.18%～119.98%,相对标准偏差(RSD)为5.01%～11.76%。该方法的灵敏度、准确度和精密度均符合农药残留测定的技术要求,适用于红茶中有机氯和拟除虫菊酯农药残留的检测。     

Preparation and characterization of core/shell particles with siloxane in the shell

The core/shell particles consisting of polystyrene core and 3-(methacryloxypropyl)-trimethoxysilane (MPS) shell were prepared in the present study by successive seeding polymerization under kinetically controlled conditions and were characterized by particle size analyser, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM image indicated that the particles containing organic siloxane presented an evident core/shell structure. Additionally, the study of XPS also revealed that MPS could be grafted onto the surface of polystyrene microspheres and the atomic ratio of C/Si on the surface of the core/shell particles (MPS-40) was very close to the ratio of C/Si in the molecule of MPS. The surface properties of the films produced from the core/shell particles were also investigated by the static contact angle method. Compared with the homopolymer of PS, the core/shell particles were more effective to create hydrophobic surface, so, the introduction of MPS was capable of obvious increase in water repellency.     

Pointwise Estimates for Linear Combinations of Gamma Operators

For linear combinations of Gamma operators G_n,r(f,x), we give an equivalent theorem with (f,t), where (f,t) are the Ditzian-Totik moduli of smoothness ( ).AMS Subject Classification (1991): 41A25, 41A36.Supported by NSF of Hebei ProvinceSupported by NSF of Hebei Province     

A novel approach for the preparation of PMMA-PDMS core-shell particles with PDMS in the shell

The core/shell particles consisting of polymethyl methacrylate (PMMA) core and polydimethylsiloxane (PDMS) shell via 3-(methacryloxypropyl)-trimethoxysilane (MPS) as the medium to link the core and shell were prepared in our present study by successive seeding polymerization under kinetically controlled conditions and were characterized by FT-IR, particle size analyzer, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).The picture of optical microscope showed the clear form of PDMS-0 and PDMS-40 (the content of PDMS in the particles), which approached to monodispersed distribution. Compared with the PMMA microspheres, PDMS-40 presented an evident core/shell structure through the observation of TEM. Additionally, the study of XPS revealed that PDMS could be grafted onto the surface of PMMA particles and the atomic ratio of C/Si on the surface of PDMS-40 was very close to the ratio of C/Si in the molecule of PDMS. The surface properties of the films produced from the core/shell microspheres also were investigated by contact angle method, contrast with the homopolymer of PMMA, the core/shell particles were more effective to form hydrophobic surface and the water repellency on the surface would be better than that of PMMA.     

Adsorption behavior of protein onto siloxane microspheres

The siloxane microspheres with core-shell structure (PMMA/PMPS) (MMA, methyl methacrylate; MPS, 3-methacryloxypropyl-trimethoxysilane) have been prepared by dispersion polymerization as described in our previous work. In this paper, the developed poly(MMA-MPS) microspheres, as a carrier, are used to investigate the adsorption behavior of bovine serum albumin (BSA) on them. The Langmuir and Freundlich models have been applied to describe the adsorption behavior. The experimental results indicated that the presence of PMPS evidently increases the adsorption rate and the amount of protein, and it also influences the interaction of BSA molecules. The adsorption of BSA on the poly(MMA-MPS) microspheres seems to be sensitive to pH and ionic strength. The fittings curves from Langmuir and Freundlich models showed that the adsorption was actually more complicated than ideal situation because one or more interactions were involved in the process. For understanding the electronic contribution, the Zeta potential was used to measure the reactive system before and after protein adsorption.     

On Approximation for Certain Operators

ＯｎＡｐｐｒｏｘｉｍａｔｉｏｎｆｏｒＣｅｒｔａｉｎＯｐｅｒａｔｏｒｓ￥（郭顺生）ＧｕｏＳｈｕｎｓｈｅｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｈｅｍａｔｉｃｓ，ＨｅｂｅｉＮｏｒｍａｌＵｎｉｖｅｒｓｉｔｙ，Ｓｈｉｊｉａｚｈｕａｎｇ，０５００１６）Ａｂｓｔｒａ...     

铋改性TiO2单晶光催化剂的制备及其完全去除酚类污染物

伴随着人类社会生产生活需要,工业污水中酚类物质的存在极易污染表面水、地下水甚至饮用水.然而,传统污水处理工艺无法对其实现完全去除,更因其稳定的化学结构和难降解特性,对生态系统和人类健康构成了巨大威胁.因此,寻求完全去除水体中酚类污染物是目前环境领域中重要的研究课题之一.二氧化钛因具有优越的物理、化学和光学性能,而被广泛应用于污染物降解研究,然而,传统TiO2光催化剂由于可见光吸收弱和光生电荷高复合率,导致污染物降解效率低,尤其是针对难降解有机污染物如酚类难以实现高效的去除.为此,本文通过引入铋纳米粒子作为TiO2单晶的改性剂,通过充分发挥铋纳米粒子的LSPR效应和TiO2单晶结构的高传导率,不仅有效地拓宽了TiO2的光响应范围(~2.8 eV),而且提高了光生电荷的分离效率,导致其优越的光催化行为.酚类污染物的降解实验表明,所合成的Bi-SCTiO2光催化剂在模拟太阳光照射下,能完全去除水体中的苯酚和对硝基酚,克服了现有以TiO2为基础的光催化剂无法实现酚类污染物完全去除的缺点.更重要的是,当使用环境水如自来水或矿泉水配制苯酚溶液,所制备的Bi-SCTiO2光催化剂仍能实现苯酚的高效降解(>98%);即使采用含有大量有机物质和微生物的长江水所配制的苯酚溶液,在模拟太阳光照射下,Bi-SCTiO2光催化剂对苯酚的降解率仍然高达96%.进一步研究发现,在各种无机离子如Na^+,K^+,Ca^2+,Cl^?,HCO3^?或SO4^2?(0.1 mM)的干扰下,制备的Bi-SCTiO2对苯酚降解率仍然高达98%以上.光催化循环实验表明,所制备的Bi-SCTiO2循环四次后,其对苯酚的降解率几乎保持不变,说明Bi-SCTiO2具有极好的循环稳定性.运用ESR和MS等分析手段,确定了酚类污染物降解的中间体结构、形态和降解路径,再结合Bi-SCTiO2催化剂的光电性能和自由基诱捕实验,提出了酚类污染物完全降解的机理.     

Surface defect kink solitons

We reveal the existence of dynamically stable nonlinear defect kink modes at an interface separating a defocusing Kerr medium and an imprinted semi-infinite lattice with a positive or negative defect covering single or several lattice sites. Increasing the number of defect sites equivalently results in a band-gap shift of lattice which in return alters the existence domains and stability properties of defect solitons. Comparing with the uniform semi-infinite lattice, the instability of kink soliton in lattice with a negative defect is significantly suppressed, especially for in-phase soliton. Our results provide an effective way for the realization of stable in-phase kink solitons.     

Cs原子62S1/2→52D5/2电四极跃迁的超精细塞曼光谱研究

利用热离子二极管加光电离技术,对Ｃｓ原子６＾２Ｓ１／２→５＾２Ｄ５／２电四跃迁超精细塞曼光谱进行了实验研究,并进行了相应的能级结构及跃迁相对强度的理论计算,对理论、实验结果进行比较和讨论。本研究对一种新的高分辨光谱方法的有效运用有指导意义。