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81.
An efficient and reliable method based on gas chromatography–mass spectrometry (GC–MS) was developed for the extraction and analysis of six phenolic endocrine disrupting chemicals (EDCs), such as 4-nonylphenol (4-NP), nonylphenol-mono-ethoxylate (NP1EO), nonylphenol-di-ethoxylate (NP2EO), 4-tert-octylphenol (4-t-OP), bisphenol A (BPA) and 4-cumylphenol (4-CP) in surface water and sediment. The method was developed by using microwave-assisted extraction (MAE), solid phase extraction (SPE) and derivatization procedure. The MAE procedures were performed by optimizing three key process factors, consisted of extraction solvent, extraction temperature and holding time, affecting the extraction efficiency from sediment samples. For SPE, various parameters that may affect the recovery efficiency of water samples, such as SPE phase cartridge, elution solvent, as well as pH of water samples, were investigated. A series of derivatization conditions, such as derivatization reagent, reaction temperature and reaction time, were improved. The method achieved good repeatability and reproducibility with relative standard deviations <13% for all target EDCs in the both samples. Satisfactory recoveries for spiked water and sediment samples ranged from 85 to 101% and 74 to 105%, respectively. The limits of quantification varied from 0.20 (4-t-OP) to 11.50 ng L?1 (NP2EO) and from 0.31 (4-t-OP) to 9.50 ng g?1 dry weight (dw) (NP2EO) for water samples and sediment samples, respectively. The established method was successfully applied to the analysis of target EDCs in surface water and sediment samples collected from Caohai site of Dianchi Lake, China. The results showed that NP1EO, NP2EO and BPA were the three dominant phenolic EDCs in the site, reaching 114, 97 and 149 ng L?1 in surface water, while 444, 186 and 178 ng g?1 dw in surface sediment, respectively. 相似文献
82.
The interaction between two similar plane double-layers for Al2(SO4)3 type asymmetric electrolytes was investigated with the aid of λ parameter method. The interaction energies for the system at positive surface potential were expanded in the power series at low and high potential, respectively. The high potential formula can be applied to 0.2 ≤ ye < y 0 ≤ 20. This almost covers with the bounds of all potential, and that the calculative method is relative simple. The accurate numeral results and V′?ξd curves were given for y 0 ≤ 20. When y 0 ≥ 5, V′ hardly change with y 0. The interaction energies between two similar plane parallel double layers for the different type electrolytes at y 0 = 1 were compared. The present results are also fit for Mg3(PO4)2 type electrolytes at negative surface potential. 相似文献
83.
In this paper, we establish a novel fractional model arising in the chemical reaction and develop an efficient spectral method for the three-dimensional
Riesz-like space fractional nonlinear coupled reaction-diffusion equations. Based on
the backward difference method for time stepping and the Legendre-Galerkin spectral method for space discretization, we construct a fully discrete numerical scheme
which leads to a linear algebraic system. Then a direct method based on the matrix
diagonalization approach is proposed to solve the linear algebraic system, where the
cost of the algorithm is of a small multiple of $N^4$ ($N$ is the polynomial degree in
each spatial coordinate) flops for each time level. In addition, the stability and convergence analysis are rigorously established. We obtain the optimal error estimate
in space, and the results also show that the fully discrete scheme is unconditionally
stable and convergent of order one in time. Furthermore, numerical experiments
are presented to confirm the theoretical claims. As the applications of the proposed
method, the fractional Gray-Scott model is solved to capture the pattern formation
with an analysis of the properties of the fractional powers. 相似文献
84.
Li Wan Xianbao Wang Shimin Wang Shaoqing Li Qin Li Rong Tian Mingjian Li 《Journal of Physical Organic Chemistry》2009,22(4):331-336
The imidazole derivatives functionalized single‐walled carbon nanotubes (SWNTs) were synthesized by a diazonium‐based reaction. We have designed and synthesized two imidazole derivatives to modify SWNTs. The resulting products were characterized by Fourier transform infrared (FT‐IR) spectroscopy, Raman spectroscopy, ultraviolet visible (UV/Vis) spectroscopy, thermo gravimetric analysis (TGA), energy dispersive X‐ray spectroscopy (EDX), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Electrochemical measurements via a cyclic voltammetry method revealed that the weak intramolecular electronic interactions presented between the attached imidazole derivatives groups and the nanotubes. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
85.
本文介绍一种新型的活塞环非圆轮廓曲线的数控仿形系统,其基本原理是以某种凸轮曲线作为刀具进给运动的基准线,应用调速原理,独立调节刀具的进给速度,使之与机床主轴保持一定的关系,在电机。反转的前提下加工出不同型号和规格的活塞环零件。为提高系统的速度调节精度和系统的鲁棒性,本文着重阐述了智能决策方法和模糊控制技术在本系统中的应用。 相似文献
86.
根据相平衡原理 ,导出了无绝热壁、刚性壁和半透壁及无化学反应、除相平衡条件约束外无其他约束的k组分和 φ相 (2≤φ≤k - 1)的多元复相平衡体系非独立变量与独立变量之间的微分关系 .任一相有温度、压力和 (k - 1)个摩尔分数共 (k+1)个变量 ,其中温度和压力是各相的公共变量 ;k组分复相平衡体系的独立变量个数最多为k ,把温度和压力作为首选的独立变量 ,独立的浓度变量最多为 (k - 2 ) ;把独立的浓度变量全部选在第一相 ,而把其他相的浓度变量都做非独立变量 ,第一相至少有一个非独立的浓度变量 相似文献
87.
用数字式冲击电流计测高电阻 总被引:1,自引:0,他引:1
介绍了数字式冲击电流计测量高值电阻的原理和方法,对两种冲击电流计的测量进行了比较,阐述了数字式冲击电流计的优点。 相似文献
88.
Zhang Shimin 《Colloid Journal》2008,70(2):168-177
The interactions between two similar plane double-layers for Na3PO4 type asymmetric electrolytes are described using hyperelliptic integrals. The mathematical treatments of hyperelliptic integrals
are much more difficult than those of elliptic integrals. The system was successfully treated with the aid of the λ parameter
method. The interaction energies for the system at positive surface potential are expanded in power series at low, moderate,
and high potentials, respectively. The accurate numeral results and V′-ξ
d
curves are given for y
0 ≤ 20 and can be used to check the validity of approximate expressions obtained. When y
0 ≥ 5, V′ hardly changes with y
0. The interaction energies between two similar plane parallel double layers for symmetric and asymmetric electrolytes at y
0 = 1 were compared; when ξ
d
→ 0, the interaction energies for Na3PO4 type electrolytes are much larger than for electrolytes of other types. The present results are also fit for FeCl3-type asymmetric electrolytes at negative surface potential.
The text was submitted by the author in English. 相似文献
89.
Shimin Jiang Sha Du Ruchun Yang Fengyan Jin Zhao-Zhao Zhou Wan-Fa Tian Xian-Rong Song Qiang Xiao 《European journal of organic chemistry》2023,26(3):e202201377
An efficient and practical approach for the synthesis of triaryl allenyl sulfones from easily accessible propargylic alcohols was developed, by using sodium sulfinates as a sulfonyl source in the presence of Brønsted acid. The reaction proceeded via allenyl carbocation as the key intermediate and was followed by a nucleophilic attack of sodium sulfinates to produce allenyl sulfones in moderate to excellent yields. 相似文献
90.
Zhien Tan Shimin Chen Mengli Zhang Xiaosheng Qu Taiping Li Aihua Zhang Yanmei He Min Ou Lihuo Long Lu Chen Fangfang Wu 《Journal of separation science》2023,46(2):2200311
Abrus mollis Hance is a traditional Chinese medicine that is widely used to treat acute and chronic hepatitis, steatosis, and fibrosis. Its therapeutic qualities of it have long been acknowledged, although the active ingredients responsible for its efficacy and the mechanisms of its action are unknown. In this study, the chemical constituents absorbed into the blood from Abrus mollis Hance were assessed by using liquid chromatography-quadrupole-time-of-flight mass spectrometry and the data was analyzed with the UNIFI screening platform. The results obtained were compared to existing chromatographic-mass spectrometry information, including retention times and molecular weights as well as known reference compounds. 41 chemical constituents were found in Abrus mollis Hance, and these included 16 flavonoids, 13 triterpenoids, five organic acids, and two alkaloids. Experimentally it was found that Abrus mollis Hance had a therapeutic benefit when treating α-naphthalene isothiocyanate-induced acute liver injury in rats. In addition, 11 blood prototypical constituents, including six flavonoids, three triterpenoids, and two alkaloids, were found in serum samples following intragastric administration of Abrus mollis Hance extracts to rats. This novel study can be used for the quality control and pharmacodynamic assessment of Abrus mollis Hance in order to assess its efficacy in the therapeutic treatment of patients. 相似文献