Review of Analytical Methods for Atmospheric Oxidants Measurements

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.     

Densities,speeds of sound,excess volumes and viscosities of binary mixtures of mtbe with tetralin and decalin at 303.15 k

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.     

若干含多硫基的配合物的合成方法及结构特征

本文综述了近年来我们合成的十二种多硫基的配合物，这些配合物含有Ｓ＾２－２，Ｓ＾２－４，Ｓ＾２－５，Ｓ＾２－６，Ｓ＾２－７等多硫革配体，总结了这些配合物中的金属配位构型，比较了各种多硫基的Ｓ－Ｓ键长及有关键角，归纳了配合物外光谱，并阐述了其中几个配合物与ＮＨ２ＮＨ２的反应性能。     

Some Strategies for the Refinement of Disordered Structures with the SHELXL-97 Refinement Program

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 …     

Contactless conductivity detection for microfluidics: designs and applications

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.     

云南松枝梢营养成分分析

对云南松健康树和纵坑切梢小蠹蛀害树枝梢营养成分进行了分析,在健康树和蛀害树松梢中分别检测出11种氨基酸和14种氨基酸。健康树松梢中元素含量变化趋势由高到低为Ca,Mg,Al,Mn,Fe,B,Zn,Sr,Ni,蛀害树松梢中无机元素含量变化趋势由高到低为Ca,Mg,Al,Fe,Mn,B,Zn,Sr,Ni,为查找纵坑切梢小蠹蛀害的原因提供依据和数据。     

The Application of NMR Spectroscopy and Chemometrics in Authentication of Spices

Spices and herbs are among the most commonly adulterated food types. This is because spices are widely used to process food. Spices not only enhance the flavor and taste of food, but they are also sources of numerous bioactive compounds that are significantly beneficial for health. The healing effects of spices are connected with their antimicrobial, anti-inflammatory and carminative properties. However, regular consumption of adulterated spices may cause fatal damage to our system because adulterants in most cases are unhealthy. For that reason, the appropriate analytical methods are necessary for quality assurance and to ensure the authenticity of spices. Spectroscopic methods are gaining interest as they are fast, require little or no sample preparation, and provide rich structural information. This review provides an overview of the application of NMR spectroscopy combined with chemometric analysis to determine the quality and adulteration of spices.     

Inorganic electrides

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.     

钼、钨系过氧化物在Sharpless烯烃环氧化反应中的应用*

钼、钨系过氧化物是非常重要的Sharpless烯烃环氧化催化剂,有着非常广泛的工业发展前景。本文综述了钼、钨系过氧化物的种类,结构,合成方法及催化活性,分析了各种钼、钨系过氧化物的特点以及在催化环氧化领域的发展现状。同时,本文还讨论了钼、钨系过氧化物催化烯烃环氧化反应的机理。评述了在催化环氧化领域中两种主要理论——Mimoun机理与Sharpless机理的争论焦点及发展现状,以及计算化学对两种理论中间过渡态的研究进展,并且重点分析了Sharpless机理的过渡态结构。此外,本文还综述了影响钼、钨系过氧化物催化剂反应活性的各种因素以及质子所产生的副反应。最后,本文对应用于催化环氧化领域的钼、钨系过氧化物未来的研究方向提出了建议。     

异丙醇的O-H伸缩振动泛频光谱和分子构像

使用高灵敏的光腔衰荡光谱(CavityRingDownSpectroscopy)技术测出了异丙醇的O-H伸缩v=4、5振动泛频光谱,每个振动能级都有三个吸收峰,被归属为分子构像的O-H伸缩泛频吸收.给出了光腔衰荡光谱的振动泛频吸收的谱带强度公式,并求得分子不同构像在不同振动能级的O-H伸缩泛频吸收的谱带强度;同时利用局域模理论,求得分子各O-H伸缩局域模振子的机械频率(X1)、非谐性(X2)以及解离能(D).用密度泛函(DFT)B3LYP/6-31+G*理论方法优化了分子的各种可能构像,验证了分子存在反式(trans)和偏转(gauche)两种稳定构像,计算的分子的O-H伸缩频率及构像稳定性同实验结果是一致的.     

Hydrophobins: Proteins that self assemble at interfaces

Hydrophobins are surface active proteins that are produced by filamentous fungi. They are interesting from a Surf Sci point of view because some of their properties as surface active proteins are quite spectacular. In this review, recent advances in understanding these properties will be surveyed. We will attempt to define what the properties are that make them unique. As an understanding of both structure and function of hydrophobins is emerging we see that this is paving the way for industrial applications as well as an understanding of their biological functions.

Major recent advances

Recently there has been a clear increase in attempts to use hydrophobins in applications. We are starting to understand their unique properties as surfactants and especially applications related to the stability and development of foams and various surface treatments are emerging. There are several new reports on molecular structures as well on mechanisms of self-assembly. Hydrophobins have functions in biology that are far from understood, but also here techniques are developing and a broader understanding is emerging.     

Nitrenium Salts in Lewis Acid Catalysis

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.     

抗生素在水环境中的光化学行为

抗生素是在水环境中广泛存在的一类新兴污染物, 近年来, 由于其“假”持久性并能引起环境菌群的抗药性而备受关注. 光化学降解是水环境中抗生素类污染物的重要消减方式. 本文总结了水环境中抗生素光化学行为研究的最新进展, 介绍了抗生素的直接、间接和自敏化光解动力学, 评述了pH和水中溶解性物质对抗生素光解的影响及典型抗生素的光降解路径与机理, 讨论了抗生素的光致毒性, 最后对抗生素在水环境中光化学行为的研究进行了展望.     

非晶态半导体中的分形结构

非晶态半导体硅(α-Si:H)薄膜作为新型的光电子材料,近年来备受关注,发展迅速。但其晶化机理有待深入探索。用分形理论所作的分析表明,在一定条件下,a-Si:H薄膜中形成的微结构具有分形性质。本文计算了分维值,讨论了a-Si:H薄膜结构弛豫(相变)与分形结构形成的关联,和非晶硅薄膜可能的晶化机理。并研究了在高真空中用透射电子显微镜(TEM)及动态方法跟踪观测a-Si:H薄膜原位(in situ)退火过程中发生的晶化现象,获得晶化形貌的显微图像。利用图像处理技术对显微像进行光电转换,A/D转换和数字计算,得到a-Si:H薄膜样品在不同退火条件下,显微象的Sandbox关系曲线。从而获得薄膜中形成不同分形结构的分维。文中给出应用分形理论对非晶态半导体薄膜进行分析的技术细节。     

闭孔泡沫塑料结构与性能研究进展

综述了近年来对闭孔泡沫塑料,主要是发泡聚烯烃的结构与性能关系研究的进展。总结了有关泡沫塑料的常见结构模型以及性能结构关系的解析式表达,并介绍了常见表征泡沫塑料结构、性能的方法以及近年来出现的新的表征手段。文章讨论了近年来研究塑料泡沫结构与性能尤其是力学性能之间关系的新结果、新进展,并对研究进行了展望。     

纳米SiO2的表面处理及其在聚合物基纳米复合材料中的应用进展

简要介绍了纳米二氧化硅(SiO2)粒子的制备方法、结构和特性,对近年来国内外纳米SiO2的表面处理方法及聚合物/SiO2纳米复合材料的制备方法进行了阐述,并针对不同改性方法和制备方法的特点加以分析比较;讨论了SiO2粒子的分散机理和增强机理,并对未来的研究内容及方向提出展望。     

Temperature modulated calorimetry and dielectric spectroscopy in the glass transition region of polymers

The results from temperature modulated DSC in the glass transition region of amorphous and semicrystalline polymers are described with the linear response approach. The real and the imaginary part of the complex heat capacity are discussed. The findings are compared with those of dielectric spectroscopy. The frequency dependent glass transition temperature can be fitted with a VFT-equation. The transition frequencies are decreased by 0.5 to 1 orders of magnitude compared to dielectric measurements. Cooling rates from standard DSC are transformed into frequencies. The glass transition temperatures are also approximated by the VFT-fit from the temperature modulated measurements. The differences in the shape of the curves from amorphous and semicrystalline samples are discussed.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthday     

Vibrational energies,bonding nature,electronic properties,spectroscopic investigations and analysis of 3-bromo-4-Chlorobenzophenone

In this present study, we investigated pharmaceutically active of 3-Bromo-4-chlorobenzophenone. Structural, electronic properties (HOMO-LUMO, MEP) are investigated using DFT tool. Vibrational spectral analysis for FT-IR and FT-Raman are made of headline molecule. Electronic transition properties are discussed with the help of UV–Vis spectral analysis. Biologically active sites are found from MEP analysis. Electron delocalization properties are studied explored from HOMO-LUMO band gap energy. Moreover, intra molecular interactions are explained from NBO method. Molecular docking studies are performed to find the interactions various pathologies. The topological properties of the electron density have been analyzed.     

Surface Reconstruction by a Coassembly Approach

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.