Polystyrene Microspheres in Tissue-Simulating Phantoms Can Collisionally Quench Fluorescence

Tissue-simulating phantoms that replicate intrinsic optical properties in a controlled manner are useful for quantitative studies of photon transport in turbid biological media. In such phantoms, polystyrene microspheres are often used to simulate tissue optical scattering. Here, we report that using polystyrene microspheres in fluorescent tissue-simulating phantoms can reduce fluorophore quantum yield via collisional quenching. Fluorescence lifetime spectroscopy was employed to characterize quenching in phantoms consisting of a fluorescein dye and polystyrene microspheres (scattering coefficients _s 100-600cm^–1). For this range of tissue-simulating phantoms, analysis using the Stern-Volmer equation revealed that collisional quenching by polystyrene microspheres accounted for a decrease in fluorescence intensity of 6-17% relative to the intrinsic intensity value when no microspheres (quenchers) were present. The intensity decrease from quenching is independent of additional, anticipated losses arising from optical scattering associated with the microspheres. These results suggest that quantitative fluorescence measurements in studies employing such phantoms may be influenced by collisional quenching.     

红外线灯泡光谱辐射特性的研究

本文研究了市售的、广泛被用于科研、工业、医疗卫生和家用电器的国产和进口的红外线灯泡，波长范围为０．３５￣０．８５μｍ和１．７２￣１６．７μｍ（５８００￣６００ｃｍ＾－１）处的光谱辐射特性，并作了比较。为它们的应用、改进设计和制造工艺、提高质量和性能，提供了理论和实验上的依据。     

红外光谱法测定农药中吡虫啉含量

通常使用高效液相色谱法检测农药中有效成分吡虫啉的含量。文章采用红外光谱法直接测定农药中吡虫啉含量,样品使用KBr压片法。吡虫啉标准品和商品吡虫啉农药的红外光谱对照实验表明：吡虫啉在939.2 cm-1处的吸收峰不受农药中其他成分的干扰,可以选择此峰为定量分析波数;吡虫啉红外光谱在947～925.8 cm-1处的峰面积与其净含量满足线性方程：Area=1.3665×10-1+2.37×10-2×c,相关系数r=0.999 53。结论：利用红外光谱快速检测农药中有效成分吡虫啉含量的方法是可行的,可以替代常规的理化分析, 能够满足快速分析的需要。     

红外光谱分辨率对气体定量分析的影响研究

利用不同分辨率(1, 2, 4, 8 cm-1)的红外光谱建立对多组分气体样本(一氧化碳、二氧化碳、一氧化氮)的定量分析模型,研究了分辨率对气体定量测量精确性的影响。研究发现：对于样本中的各气体组分,在合适的分辨率下都有其最佳的测量精确性;而对于模型的整体精确性,在高分辨率1和2 cm-1以及低分辨率8 cm-1时模型都有较好的精确性,各组分相关系数(r)均值达到0.999 5以上,校正均方根误差(RMSEC)和验证均方根误差(RMSEP)的均值分别为18.36和15.43以下,而在分辨率为4 cm-1时,模型测量精确性陡然降低,r均值降到0.989 66,RMSEC均值为90.37,RMSEP均值为64.33。实验结果表明：光谱分辨率对气体定量分析有明显的影响。为提高定量分析测量的精确性,需要针对不同的待测气体和应用场合采用合适的分辨率参数。     

Quantitative Determination of Reactive Species in Alkali Halide Disks

Abstract

As part of an infrared investigation of the kinetics of the reactions of KMnO₄ in a KI disk and of KIO₄ in a KI disk, the stoichiometry of the two reactions was needed. A previous study¹ has shown that MnO₄ ^? reacts in a KI matrix to produce IO₄ ^? (which then reacts further to form IO₃ ^?) and MnO₂. Iodate ion is the only observable product in the reaction of IO₄ ^? in a KI matrix¹. The infrared absorption at 740cm^?1, which is due to the presence of IO₃ ^?, was found to obey the Beer-Lambert Law. However, calibration curves for KMnO₄ in KI and for KIO₄ in KI could not be obtained because both species reacted with the dispersing medium during the preparation of the disk¹. It was also observed that no immediate reaction occurred when KBr or KC1 disks containing KMnO₄, or KIO₄ were prepared. Thus, an extrapolation method was sought which would permit the estimation of calibration curves for the reactive species.     

吉林长白山硅藻土的红外光谱研究

对长白山硅藻土在 10 0～ 1330℃温度范围进行热处理并开展红外光谱研究 ,结果表明经 5 0 0℃热处理样品开始出现 374 5cm- 1 峰 ,在 90 0℃达到最大 ,12 0 0℃消失 ,此时硅藻土转变成方石英。对 374 5cm- 1 峰所反映的以孤立Si—OH形式存在的水的含量进行了半定量计算 ,表明这种OH除存在于样品表面外 ,还存在于内部的结构缺陷处 ,并推测硅藻土转变成方石英与这种孤立Si—OH的消失有关     

The Infrared Spectrum of Solid Chlorotrifluoromethane

The Infrared spectrum of solid chlorotrifluoromethane (CF₃Cl) has been studied and compared with that of matrix-isolated CF₃Cl. Crystal field splitting patterns of the strongest modes ν₁ and ν₄ suggest the crystal structure to be orthorhombic with a C_2v factor group and two molecules per unit cell located on C_s sites.     

基于Elman网络的近红外光谱技术多组分定量分析研究

研究了Elman神经网络(反馈神经网络,Recurrent Network)在近红外光谱定量分析中的应用。以饲料样品为实验材料,采用Elman网络建立了饲料中苯丙氨酸(Phe)、赖氨酸(Lys)、酪氨酸(Tyr)和胱氨酸(Cys)四种氨基酸含量的近红外光谱定量分析模型。用偏最小二乘法(partial least squares ,PLS)将原始数据压缩为主成分,取前3个主成分的12个吸收峰值输入Elman网络,网络中间层神经元个数为47。Elman网络模型对样品4个氨基酸含量的预测决定系数(r2)分别为0.960,0.981,0.979,0.952。表明所建Elman网络预测模型通过近红外光谱能够较准确预测饲料中苯丙氨酸、赖氨酸、酪氨酸和胱氨酸四种氨基酸的含量,为通过近红外光谱技术进行多组分定量分析提供了新思路。     

Infrared facility at the Canadian light source

The Canadian Light Source (CLS) is constructing two beamlines for Infrared Spectroscopy using synchrotron radiation (IRSR). One will supply mid-Infrared (2–25 μ) light to a Fourier Transform Infrared (FTIR) spectrometer and microscope for biological applications. The second will have a high resolution FTIR spectrometer for gas-phase and surface spectroscopy in the far-Infrared (beyond 25 μ). The Infrared beamlines will use dipole bending magnet radiation from a special bend magnet port design which provides a 50 mrad square acceptance. Issues with the first mirror and photon mask design, as well as the beamline layout and features are discussed.     

老鹳草中药材红外光谱的分析与鉴定

采用红外光谱、二阶导数光谱和二维相关红外光谱对来自黑龙江、吉林、辽宁三省的老鹳草中药材进行了分析。不同产地的老鹳草的红外光谱都具有1 730和1 337 cm-1等表征鞣质类成分的特征吸收峰和1 618和1 318 cm-1波数表征草酸钙的特征峰。其中还发现在1 370 cm-1的C—H弯曲振动区和1 230 cm-1的C—O伸缩振动区三产地老鹳草具有一定的差异性。在高分辨的二阶导数谱中, 1 509,1 204,764和763 cm-1附近的表征鞣质类成分的吸收峰更明显,三产地老鹳草在CO羰基伸缩振动区表征了脂肪类化合物的不同;尤其是在二维相关光谱上,各自的自动峰具有显著的差异性,黑龙江的老鹳草出现了7个自动峰,其中1 621 cm-1处自动峰最强;而在吉林和辽宁产地的老鹳草中同样出现了4个自动峰,前者1 580 cm-1处的自动峰最强,后者在1 649 cm-1处自动峰最强。该方法直观、简单、方便、快速,可以作为鉴别和鉴定同种不同产地老鹤草的一种新方法。     

非理想化学计量比氧化铀的拉曼和红外光谱

测量了七种非理想化学计量比的UO₂+x(0＜x＜0.66)及UO₂和U₃O₇等理想化学计量比氧化铀的拉曼和红外光谱,并进行了对比分析,其中U₃O₇和U₃O₈之间UO₂+x的分子振动光谱为首次报道。拉曼光谱结果显示,随着UO₂+x中x值的增加,UO₂特征峰中的578和1 150 cm-1峰强度快速减弱,当x=0.19时,这两峰基本消失,可视为准完美萤石晶体结构UO₂的标志。445 cm-1峰强度在减弱的同时变宽并偏移,当x=0.32时,该峰已偏移至459 cm-1处,同时在～630 cm-1出现一弱肩峰,这与四方相U₃O₇的特征峰一致。当x≥0.39时,459 cm-1峰发生分裂,在235和754 cm-1处出现新峰并增强,其特征逐渐与正交相的α-U₃O₈接近。但直至x=0.60时,与α-U₃O₈相比其333,397,483和805 cm-1峰仍不突出。红外光谱结果显示,随着UO₂+x中x值的增加,UO₂位于400～570 cm-1区间的强吸收特征谱带逐渐分裂为～421和～515 cm-1两峰并增强,同时UO₂在～700 cm-1的弱吸收峰逐渐消失,～645 cm-1处的肩峰逐渐显现,出现的这三个峰正是U₃O₇的特征红外吸收峰。当x≥0.39时,在744 cm-1出现一强吸收峰并增强,该峰是α-U₃O₈的最强特征峰。但即使x=0.60时,～645 cm-1峰仍然存在,同时～515 cm-1峰也未明显分裂成485和535 cm-1峰,这表明UO_2.60仍处于四方相和正交相的过渡阶段。上述结果表明,随着x值的增加,UO₂+x的晶体结构发生变化,每次变化均在拉曼和红外光谱中得到体现。通过对比各特征峰相对强度和位置的变化情况,可很好区分和表征不同的氧化铀。     

Raman and Infrared Spectroscopic Study of the Borate Mineral Kaliborite

We have studied the mineral kaliborite. The sample originated from the Inder B deposit, Atyrau Province, Kazakhstan, and is part of the collection of the Geology Department of the Federal University of Ouro Preto, Minas Gerais, Brazil. The mineral is characterized by a single intense Raman band at 756 cm^?1 assigned to the symmetric stretching modes of trigonal boron. Raman bands at 1229 and 1309 cm^?1 are assigned to hydroxyl in-plane bending modes of boron hydroxyl units. Raman bands are resolved at 2929, 3041, 3133, 3172, 3202, 3245, 3336, 3398, and 3517 cm^?1. These Raman bands are assigned to water stretching vibrations. A very intense sharp Raman band at 3597 cm^?1 with a shoulder band at 3590 cm^?1 is assigned to the stretching vibration of the hydroxyl units. The Raman data are complimented with infrared data and compared with the spectrum of kaliborite downloaded from the Arizona State University database. Differences are noted between the spectrum obtained in this work and that from the Arizona State University database. This research shows that minerals stored in a museum mineral collection age with time. Vibrational spectroscopy enhances our knowledge of the molecular structure of kaliborite.     

PLS-GRNN法近红外光谱多组分定量分析研究

研究了偏最小二乘(partial least squares ,PLS)与广义回归神经网络(generalized regression neural networks, GRNN)联用在近红外光谱多组分定量分析中的应用。以饲料样品为实验材料,采用PLS-GRNN法建立了饲料中水溶性氯化物、粗纤维、脂肪三项组分含量近红外光谱定量分析模型。马氏距离法剔除强影响点和奇异点,用PLS法将原始数据压缩为主成分,取8个主成分吸收峰与4个原始图谱特征峰值输入GRNN网络,网络光滑因子σ_i为0.1。PLS-GRNN模型对样品3个组分含量的预测决定系数(r2)分别为：0.984 0,0.987 0,0.983 0;样品平行扫描光谱预测值的标准偏差分别为：0.003 26,0.065 5,0.031 4。结果表明所建PLS-GRNN模型通过近红外光谱能够准确预测饲料中水溶性氯化物、粗纤维、脂肪三项组分含量,为近红外光谱进行多组分定量分析提供了新思路,同时为解决近红外快速检测技术在预测组分含量较低的样品时误差相对较大的问题提供了可靠的方法。     

紫外光引发阳离子聚丙烯酰胺的红外光谱研究

以丙烯酰胺(AM)、 丙烯酰氧基乙基三甲基氯化铵(DAC)、 丙烯酸丁酯(BA)为单体,采用紫外光引发聚合制备阳离子聚丙烯酰胺P(AM-DAC-BA)。 采用紫外光谱和红外光谱研究其结构特征;分析AM,DAC,BA,P(AM-DAC-BA)的红外光谱中的典型红外振动频率的归属。 通过与单体红外光谱比较得出：由于聚合产物的对称性增加,聚合产物红外光谱更加简单。 P(AM-DAC-BA)的特性粘度随着光强、 BA含量、 光引发剂浓度、 光照时间的增加而增加。 选取AM,DAC,BA中的—CONH₂,—COOCH₂(CO), —COOCH₂—(C—O—C),—CH₂—N+(CH₃)₃基团吸收峰为特征吸收峰,随着光强、 BA含量的增加,特征峰面积增加;随着光引发剂浓度增加特征峰面积却呈现减少趋势;随着光照时间增加,峰面积是先减小后增加。 但不同P(AM-DAC-BA)在红外光谱上对应的特征吸收峰的峰型类似,特征峰位置基本一致。     

甘草中甘草苷和甘草酸红外定量模型特征变量的筛选与解析

借助变量筛选方法可以从复杂的光谱背景下选择部分变量构建定量预测模型,在一定程度上提高建模变量的解释性。然而模型解释性的提高并不意味着建模变量有确切的理化意义。本研究以甘草中红外定量预测模型为载体,解析移动窗口偏最小二乘(mwPLS)、组合间隔偏最小二乘(siPLS)和竞争自适应抽样方法(CARS)三种变量筛选方法所得变量与目标成分化学特征的相关性,比较不同变量筛选方法下所筛变量解释性的差异。结果表明,mwPLS优先筛出黄酮和皂苷两类成分红外光谱上区别明显的苯环骨架振动和皂苷母核上甲基取代基弯曲振动所对应的波段,siPLS筛出了黄酮类成分的(φ)C—O,(φ)CC, (φ)C—H伸缩振动的特征区间组合和皂苷类成分的C—O,C—H,O—H伸缩振动的特征区间组合。相对于以上两种变量筛选方法,CARS筛选得到的变量能够更好地归属于甘草苷和甘草酸在中红外1 000～4 000 cm-1特征区的特征峰,而且基于CARS筛选的变量建模,模型的预测性能得到了提高。因此,CARS筛选的变量能实现目标成分红外特征区大部分化学特征的解析,有利于增强模型的解释性。     

Reflection-Absorption Infrared Spectroscopy Study of Polyacrylonitrile on Copper at Elevated Temperature

Reflection-absorption infrared spectroscopy (RAIR) has been used to investigate the chemical structural changes in Polyacrylonitrile (PAN) film adsorbed on copper at 200°C for different time. The formation of an almost fully conjugated C-C=C backbone occurs after heating for only 2 h due to the catalytic effect of copper. The freely dangling cyano groups in PAN molecules initially coordinate to copper surface through the triple bond in π-bonded orientation, then convert to [sgrave]-bonding through the donation of the lone pair of electrons of nitrogen. It is suggested that this transition of the types of coordination would relate to the different geometries of PAN on copper during heating. Since the nitrile complexing and cyclization occur at the same time, the reaction process for the pyrolysis of PAN on copper surface is different from that in the bulk.     

Study on Infrared Spectral Radiance by Remote Fourier Transform Infrared Spectroscopy

Abstract

Infrared emission spectra emitted by high luminosity infrared pyrotechnics have been observed remotely using the Fourier transform infrared spectroscopy. The primary purpose of the study is to determine infrared spectral radiance distribution, their time—resolved spectra and integrated emission energy. The spectra have been recorded between 4000 – 800cm^?1 region with spectral resolution of 4cm^?1. The study is very important for many applications.     

时间分辨偏振红外光谱及其应用

时间分辨偏振红外光谱已被广泛应用于研究光化学过程中的分子结构动力学. 通过测定瞬态物质跃迁偶极矩之间的角度等结构信息,可以提供光化学过程中伴随的电荷分布、分子结构和构象变化等动态信息. 包括简要介绍时间分辨偏振红外光谱技术的原理和应用：(i) 时间分辨偏振红外光谱概述;(ii) 时间分辨偏振红外光谱的原理及其优势;(iii) 利用时间分辨偏振红外光谱探测多种化学动力学过程,例如蛋白质构象动力学、激发态的电子局域化和光致异构化等;(iv) 时间分辨偏振红外光谱的局限和发展前景.     

Infrared spectroscopy of mass-selected metal carbonyl cations

Metal carbonyl cations of the form are produced in a molecular beam by laser vaporization in a pulsed nozzle source. These ions, and their corresponding rare gas atom “tagged” analogs, , are studied with mass-selected infrared photodissociation spectroscopy in the carbonyl stretching region and with density functional theory computations. The number of infrared-active bands, their frequency positions, and their relative intensities provide distinctive patterns allowing determination of the geometries and electronic structures of these complexes. Cobalt penta carbonyl and manganese hexacarbonyl cations are compared to isoelectronic iron pentacarbonyl and chromium hexacarbonyl neutrals. Gold and copper provide examples of “non-classical” carbonyls. Seven-coordinate carbonyls are explored for the vanadium group metal cations (V⁺, Nb⁺ and Ta⁺), while uranium cations provide an example of an eight-coordinate carbonyl.     

Infrared Difference Spectroscopy as a Physical Tool to Study Biomolecules

Abstract

This brief review focuses on the information that can be obtained for biomolecules, especially proteins, by using the technique infrared-induced difference spectroscopy.