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本文在文献[1]的基础上,对多环芳烃(PAH)图进行了数学论证,论证了PAH线性符号系统即特征数的唯一性,结构预测计数中判别全芳性的偶数定理,特征数连接矩阵变换定理和程序设计的离散数学策略等。首次提出了一揽子分子轨道法(WMO)及蕴含分子一切拓朴信息的线性符号,实现了有真实化学意义的PAH结构预测计数,开拓了对整类化合物自动计算的先例,并已成功地在我们实验室的结构致癌性能的研究等方面,常规地应用。 相似文献
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不同垃圾焚烧炉排放的PM10中多环芳烃的研究 总被引:3,自引:2,他引:1
对大气可吸入颗粒物采样器进行改装,建立了垃圾焚烧炉烟气中PM10采样系统,并采集了三家垃圾发电厂焚烧炉排放烟气中的可吸入颗粒物。利用GC-MS对可吸入颗粒物中的16种多环芳烃进行定量研究,获得了多环芳烃的质量分数和浓度,并对不同环数的芳烃进行了比较,分析了不同样品中的多环芳烃的毒性参数。结果表明,颗粒物中的多环芳烃主要集中在4环、5环和6环,3环和2环所占比例较少;与燃煤电厂相比,垃圾焚烧发电厂排放的烟气中多环芳烃的浓度和毒性参数更高。 相似文献
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正橡胶制品存在于玩具、电子电气产品、纺织品与食品接触材料等各类产品中,如各类密封部件、鞋底、服装箱包配饰、炊具把手、自行车把手和汽车轮胎等。橡胶制品中多环芳烃主要来源于填充油、炭黑以及煤焦油和某些石油下游产品,这些助剂赋予了橡胶制品特殊的性能,但也带来了多环芳烃的危害,多环芳烃(PAHs)是最早发现的具有"致癌、致畸、致突变"作用的环境污染物之一。为此,欧盟和美国纷纷发布了橡胶制品中多环 相似文献
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从M区键级、超离域能和致癌活性的对应关系,结合致癌反应湾区历程对用句法模式识别方法找出的多环芳烃强致癌信息特征曲线进行了理论解释。 相似文献
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建立了表面增强拉曼/主成分分析快速筛查食品接触材料中4种多环芳烃的分析方法。采用纳米银溶胶作为增强基底,碘化钾为絮凝剂,实现了4种多环芳烃(芘、荧蒽、苯并[b]荧蒽、苯并[k]荧蒽)的表面增强拉曼分析。针对食品接触材料中4种多环芳烃拉曼谱峰重叠难以鉴别区分的问题,采用主成分分析法分别对同浓度多环芳烃、不同浓度多环芳烃以及多环芳烃混合样品进行分析。结果表明,4种多环芳烃均可得到较好的鉴别。该方法成功用于食品接触材料迁移液中4种多环芳烃的快速筛查。 相似文献
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《Physics and Chemistry of Liquids》2012,50(6):561-568
Measurements of densities, speeds of sound, excess volumes and viscosities of binary mixture of methyl tert-butyl ether with tetralin and decalin are reported at 303.15?K over the entire range of composition. Excess volumes are measured using batch dilatometer technique. Sound speeds are obtained using ultrasonic interferometer. Densities are computed from excess volume data. Isentropic compressibilities are derived from density and sound speed data. Speeds of sound are evaluated on the basis of Jacobson's free length theory and Schaff's collision factor theory. The predicted values are in good agreement with the experimental results. The viscosity data are analysed on the basis of corresponding states approach. Excess volumes and deviation in isentropic compressibilities are negative and deviation in viscosities are positive over the entire composition range. The experimental results are discussed in terms of possible molecular interactions between unlike molecules. 相似文献
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Ng Seik Weng 《结构化学》2005,24(12):1425-1439
1 INTRODUCTION finement stage. The person performing the crysta- llographic manipulations works on numerical data The high degree of order in the arrangement of that are quite different from the diffraction images atoms in a crystal is a fundamental characteristic of on a computer terminal, and most often does not even the crystalline state, an ideal crystal being envisaged see the images. to be constructed of regularly-stacked unit cells, each The refinement program, SHELXL-97[1], has … 相似文献
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Inorganic electrides are a novel kind of ionic compounds in which the anions are electrons confined in a complex array of cavities or channels and the cations are nanoscale arrays of alkali metal ions that provide charge balance. In electrides the donated electron behaves like a low-density correlated electron gas, whereby the dimensionality of the electron gas and its electronic and magnetic properties are determined by the topology of the cavities in the host matrix. Unlike traditional electrides, in which alkali cations are encapsulated within an organic cage, inorganic electrides are thermally stable. The current inorganic electrides based on alkali metal loaded zeolites can be designed as useful reduced-dimensionality materials. Inorganic electrides are powerful reducing agents, and they are able to reduce small aromatic molecules to the radical anions within the channels of the zeolite. 相似文献
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The most relevant defects in glasses and thin films on glasses are categorized and investigated by the appropriate microanalytical
techniques. Knots, which are local glassy inclusions, are described in greater detail. The combination of EPMA/EDX and LA-ICP-MS
allow the determination of element concentrations in the defect down into the low ppm range, thus finally enabling the identification
of a special source of the defect from otherwise non distinguishable refractories. The results of analysis of stones and striae
are reported and defect sources are discussed. Local defects in thin films are characterized which can be explained by high
intrinsic compressive stress in the films. Typical glass and thin film defects are used to illustrate the problem-solving
process in industrial labs. 相似文献
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Ya Zhao Li Liu Hanying Zhao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(31):10687-10691
Materials with switchable surfaces, capable of changing surface properties under external stimuli, are playing a pivotal role in many applications, such as tissue engineering, biosensors, and drug/protein delivery. In this research silica particles with patterned and switchable surfaces are fabricated. Surface micelles on silica particles are formed by coassembly of polymer brushes and “free” block copolymer chains in a selective solvent. The cores of the surface micelles are crosslinked by anthracene photodimerization. After quaternization of the coronae, amphiphilic surface micelles are prepared. The surface micelles are able to rearrange in different media. After treatment with an organic solvent, the surfaces of silica particles are occupied by hydrophobic polymer components; in aqueous solution, the positively charged polymer chains are on the surfaces. The switching of the surface micelles results in changes in surface composition and wetting behaviors. 相似文献
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针对大面积功率器件软钎料的失效问题,运用扫描电子显微镜(SEM)分析了SnPb软钎料的微观结构并运用能谱仪对其进行成分分析,找出了失效的主要原因:对软钎料进行刚玉抛光后,未能将残留在软钎料内的Al2O3成分完全去除,以至于器件的可焊性变差.根据分析提出了改进意见,较好地解决了SnPb软钎料的失效问题. 相似文献
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Seyedhosein Payandeh Damian Goonetilleke Matteo Bianchini Jürgen Janek Torsten Brezesinski 《Current Opinion in Electrochemistry》2022
The recent developments in the application of single-crystalline (SC) cathode materials in solid-state batteries are discussed in this mini-review. The characteristics of SC and poly-crystalline (PC) cathode materials are explored, with emphasis on the kinetic and mechanical properties. The critical factors influencing their performance in liquid electrolyte and solid-state battery cells are investigated. Finally, the advantages and disadvantages of both morphologies are discussed and considerations to ensure a fair comparison between SC and PC cathodes in different systems are raised. 相似文献
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J. A. Hodgeson 《International journal of environmental analytical chemistry》2013,93(2):113-132
Abstract Instrumental and manual methods currently available for the measurement of atmospheric oxidants are surveyed. Techniques used in the United States are emphasized and their advantages and disadvantages are discussed. Commercial systems are evaluated in terms of general operating principles rather than of specific instruments. The ability of these techniques to meet the measurement requirements defined by U.S. Federal air quality oxidant criteria are discussed. Alternative chemical techniques that may have some advantages over the neutral, buffered KI procedure are discussed. Also some attractive, alternative instrumental procedures that are ozone-specific are presented. These systems are based on chemiluminescence and ultraviolet absorption photometry. Electrochemical and colorimetric methods for total oxidant measurements are compared. Finally, some data are presented on relationships of ozone and total oxidants. 相似文献
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Different methods for construction of contactless conductivity detectors (CCD) for microchip electrophoresis device are described in this review. This includes three main schemes of CCD for microchips, such as (i) the detection electrodes are placed along the microchannel from outside of the microchip and they are insulated from the channel by the cover lid of microchip device; (ii) the electrodes are placed across of the microchannel in the same plane and they are insulated by thin separation channel walls and (iii) electrodes are buried in widened part of microchannel and they are insulated from solution by ultrathin layer of silicon carbide. Specific issues related to the CCD on microfluidics are discussed, such as an influence of shape and magnitude of ac voltage and placement of electrodes and their insulation. Various applications for security, pharmacological, bioassays and food analysis purposes are described. 相似文献
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Meera Mehta Jose M. Goicoechea 《Angewandte Chemie (International ed. in English)》2020,59(7):2715-2719
Molecular compounds featuring nitrogen atoms are typically regarded as Lewis bases and are extensively employed as donor ligands in coordination chemistry or as nucleophiles in organic chemistry. By contrast, electrophilic nitrogen‐containing compounds are much rarer. Nitrenium cations are a new family of nitrogen‐based Lewis acids, the reactivity of which remains largely unexplored. In this work, nitrenium ions are explored as catalysts in five organic transformations. These reactions are the first examples of Lewis acid catalysis employing nitrogen as the site of substrate activation. Moreover, these compounds are readily accessed from commercially available reagents and exhibit remarkable stability toward moisture, allowing for benchtop transformations without the need to pretreat solvents. 相似文献