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671.
城市污水的三维荧光指纹特征 总被引:15,自引:1,他引:14
传统表征有机物含量的水质参量如化学需氧量(COD)和生化需氧量(BOD)等只能表示总量,无法展示有机物成分.荧光光谱可以作为一种新型的水质表示方法,它像指纹一样与水样一一对应,被称为水质荧光指纹.采用三维荧光光谱(EEM)技术研究了城市污水荧光指纹特征,结果表明城市污水具有4个典型荧光区,各区的荧光中心、强度以及1区荧光中心λex=280 nm,λem=340 nm与2区荧光中心λex=225 nm,λem=340 nm的荧光强度的比值可以作为城市污水的主要荧光指纹特征.荧光指纹包含了大量污染物信息,通过与城市污水中典型污染物质的荧光光谱的比对,初步确定了各荧光区可能的荧光信号来源.荧光指纹法可表示有机物类型和含量,可作为化学需氧量和生化需氧量等参量的有益补充. 相似文献
672.
673.
指纹信息识别技术与应用 总被引:5,自引:1,他引:4
综合叙述了指纹信息识别技术的发展与应用,包括一般指纹识别系统的原理,指纹数据的产生办法,指纹图像的预处理,以及提取特征、分类鉴定的各种方法,例如:结构方法,统计方法,人工神经网络方法,光电混合方法等,并进行了比较和分析。 相似文献
674.
芳香烃作为城市大气臭氧(O3)和二次有机气溶胶(SOA)的重要前体物, 由于其对大气二次污染、气候变化及人体健康具有重要影响, 因此芳香烃氧化机理研究成为当前大气环境化学领域最具挑战的热点研究之一. 本文综述了芳香烃氧化机理的研究成果, 详细讨论了它们与OH自由基在高低氮氧化物条件下的各反应通道和影响因素, 重点关注近年来芳香烃氧化反应研究中的新发现和新理论. 芳香烃的大气氧化反应起始由OH自由基主导, 根据其反应产物主要分为醛通道、酚通道、双环RO2通道和环氧化物通道. 随着形成多羟基化合物、烷氧自由基环氧化、双环过氧自由基分子内氢转移、醛类化合物氢转移、CO-loss生成低碳产物等新理论的提出, 对芳香烃氧化的理解虽然有所提高, 但反应过程仍存在碳质量不守恒和自由基不闭合的问题, 导致对后续O3和SOA形成机制的认识还十分有限. 理论计算和实验室模拟是目前芳香烃氧化机理研究的主要手段. 质谱法和光谱法是芳香烃氧化产物最常用的测量技术, 在线质谱技术尝试从分子水平上捕捉示踪性中间产物的转化, 对揭示芳烃氧化机理具有重要作用. 随着示踪物测量技术的发展, 特别是色谱-质谱联用技术为中间产物的精准测量和芳香烃氧化机制的完善开拓了新方向. 在此基础上, 厘清芳烃氧化中的碳平衡和自由基收支等关键科学问题、探究实际大气中芳香烃的环境效应有望成为未来该领域的重点研究方向. 相似文献
675.
Yuli Sang Jingyu Liu Lei Shi Xiulan Wang Yueqiang Xin Yanjun Hao Li Bai 《Molecules (Basel, Switzerland)》2021,26(21)
The objective of this study was to establish the chromatographic fingerprints of the essential oil (EO) from Stellera chamaejasme flowers collected from various natural sites by gas chromatography (GC) combined with chemometric methods. The EO was obtained by hydrodistillation, and its chemical composition was analyzed by gas chromatography−mass spectrometry (GC−MS). Most components were identified as ketones and the relatively high-content components were fitone (38.973%), n-hentriacontane (5.807%), myristic acid (4.944%) and phytol (3.988%). In addition, the repellent activities of the EO from S. chamaejasme flowers and its four main chemical compounds were evaluated against three stored product pests (Tribolium castaneum, Lasioderma serricorne, Liposcelis bostrychophila) for the first time. In this work, the EO and the four chemical compounds showed a repellent effect against three storage pests after 2 and 4 h exposure. The experimental method and repellent activity of S. chamaejasme flower EO could provide a basis for the development of botanical pesticide and the utilization of the rich plant resources of S. chamaejasme in the future. 相似文献
676.
Lu-Lu Deng Xu-Dong Xie Jiang Li Dao-Ping Wang Xiao-Jiang Hao Gang Chen Shu-Zhen Mu 《Molecules (Basel, Switzerland)》2021,26(21)
To scientifically clarify the hepatoprotective constituents of Fructus Schizandrae chinensis, eleven batches samples of total dibenzocyclooctadiene lignans (TDL) from Schisandra chinensis were prepared by using the optimum extraction technique. Characteristic high-performance liquid chromatography (HPLC) chromatograms were obtained through HPLC analysis technology, and the hepatoprotective effects of the eleven batches of TDL were evaluated by MTT assay. Based on the chemical and biological activity results, the spectrum-effect relationship between the characteristic HPLC fingerprints and the hepatoprotective effect of TDL was established using Minitab 16.0 data analysis software. On the basis of the spectrum-effect relationship, thirteen compounds (1–13) were obtained from the TDL by chemical natural product chemical separation and purification technology, and their structures were identified on the basis of the spectral data and the literature. Based on these compounds, thirteen common peaks among the thirty-three chromatographic peaks in the above HPLC fingerprints were identified. Our findings showed that some components, including, schisandrin B (2), schisandrin A (3), and schisandrol B (7) had significant roles in promoting hepatoprotective activity. Preliminary verification of the spectrum-effect relationship of TDL from S. chinensis was carried out, and the results confirmed that the activity of a composite of these three key components in optimal ratios was better than that of any individual compound, which potentially confirmed the reliability of the spectrum-effect relationship and the synergistic effects of traditional Chinese medicine. 相似文献
677.
Nina Huynh Emilie Caupos Caroline Soares Peirera Julien Le Roux Adle Bressy Rgis Moilleron 《Molecules (Basel, Switzerland)》2021,26(23)
Non-target screening (NTS) has gained interest in recent years for environmental monitoring purposes because it enables the analysis of a large number of pollutants without predefined lists of molecules. However, sample preparation methods are diverse, and few have been systematically compared in terms of the amount and relevance of the information obtained by subsequent NTS analysis. The goal of this work was to compare a large number of sample extraction methods for the unknown screening of urban waters. Various phases were tested for the solid-phase extraction of micropollutants from these waters. The evaluation of the different phases was assessed by statistical analysis based on the number of detected molecules, their range, and physicochemical properties (molecular weight, standard recoveries, polarity, and optical properties). Though each cartridge provided its own advantages, a multilayer cartridge combining several phases gathered more information in one single extraction by benefiting from the specificity of each one of its layers. 相似文献
678.
Saturnino Calvo-Losada Jos Joaquín Quirante Dimas Surez Toms Luis Sordo 《Journal of computational chemistry》1998,19(8):912-922
A detailed investigation of the reaction path for the thermal rearrangement of 3,4-dihydro-1aH-azirine[2,3-c]pyrrol-2-one to yield a cyanoketene–formaldimine complex is carried out at the MP2/6-31G* and B3LYP/6-31G* levels of theory. The ring opening of the five-membered pyrrolinone ring and the formation of the nitrile group takes place in a concerted manner, presenting a significant strain energy release and allowing for an electronic stabilization by coarctate conjugation of the transition structure (TS). These two factors make possible a moderate energy barrier. Although the structural features B3LYP/6-31G* theoretical levels, it is found that the MP2 energy barrier (28.8) CCSD(T)/6-31G*//MP2/6-31G* value (17.1 kcal/mol). The complex electronic rearrangement can be rationalized using the theory of coarctate transition structures developed by Herges as the evolution of an azirine structure without referring to a hypothetical vinyl nitrene intermediate. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 912–922, 1998 相似文献
679.
Dr. Massimo Serra Prof. Marco Terreni Dr. Eric Bernardi Prof. Lino Colombo 《European journal of organic chemistry》2023,26(5):e202201394
After the first synthesis reported in 1994, azabicycloalkane amino acids have raised increasing interest, becoming one of the most important classes of constrained dipeptide mimics. Their incorporation into peptidomimetic structures allowed the obtainment of a wide range of biologically active compounds. Over the years, different research groups have worked at the development of synthetic strategies to gain these rigid dipeptide surrogates, nevertheless, methods affording functionalized and “easy-to-functionalize” derivatives are quite less described. The presence of a derivatizable azabicycloalkanone core could allow the introduction of chemical modifications aimed to improve the pharmaceutical properties of a biologically active compound without the need for redesigning its chemical synthesis. This account has collected and critically surveyed relevant approaches to the synthesis of functionalized azabicycloalkane amino acids, focusing the attention on the period of 2010 to the present. Moreover, recent applications of these compounds in drug discovery will be discussed. 相似文献
680.
Si-Yu Wang Zhong-Wei Zhang Liu Yuan Prof. Dr. Yi Jin Dr. Cong-Hai Zhang Prof. Dr. Jun Lin 《European journal of organic chemistry》2023,26(3):e202201268
An efficient and simple procedure for the preparation of 2-pyridinone is reported. The obtained products contained various bicyclic 2-pyridinones and multi-substituted 6-amino-2-pyridinones. This approach employed 3-hydroxy-2-aryl acrylate and nitro ketene aminal as substrates, and the corresponding 2-pyridinones were obtained in good to excellent yields. This method may be used for the synthesis of bicyclic 2-pyridinones, as well as multi-substituted complex 2-pyridinones. 相似文献