The application of Fourier transform mid-infrared(FTIR) spectroscopy to identify variation in cell wall composition of Setaria italica ecotypes

Cell wall composition in monocotyledonous grasses has been identified as a key area of research for developing better feedstocks for forage and biofuel production.Setaria viridis and its close domesticated relative Setaria italica have been chosen as suitable monocotyledonous models for plants possessing the C4 pathway of photosynthesis including sorghum,maize,sugarcane,switchgrass and Miscanthus×giganteus.Accurate partial least squares regression（PLSR）models to predict S.italica stem composition have been generated,based upon Fourier transform mid-infrared（FTIR）spectra and calibrated with wet chemistry determinations of ground S.italica stem material measured using a modified version of the US National Renewable Energy Laboratory（NREL）acid hydrolysis protocol.The models facilitated a high-throughput screening analysis for glucan,xylan,Klason lignin and acid soluble lignin（ASL）in a collection of 183 natural S.italica variants and clustered them into classes,some possessing unique chemotypes.The predictive models provide a highly efficient screening tool for large scale breeding programs aimed at identifying lines or mutants possessing unique cell wall chemotypes.Genes encoding key catalytic enzymes of the lignin biosynthesis pathway exhibit a high level of conservation with matching expression profiles,measured by RT-q PCR,among accessions of S.italica,which closely mirror profiles observed in the different developmental regions of an elongating internode of S.viridis by RNASeq.

Detection of Broad Bean Diseases by Fourier Transform Infrared Spectroscopy Combined with Curve Fitting

Fourier transform infrared （FTIR） spectroscopy was used to study diseased leaves in broad bean. Results showed that the infrared spectra of different broad bean diseased leaves were similar, which were mainly made up of the vibrational absorption bands of protein,lipid and polysaccharide.There were minor differences in-cluding the spectral peak position, peak shape and the absorption intensity in the range of 1 800-1 300 cm-1. There were obvious differences among their second derivative spectra in the range of 1 800-1 300 cm-1. After the procedure of the Fourier self-deconvolution and curve fitting of health bean leaves and broad bean diseased leaves in the range of 1 700-1 500 cm-1, three sub-peaks were obtained at 1 550 cm-1 （protein amide Ⅱ band）, 1 605 cm-1 （lignin） and 1 650 cm-1 （protein amide I band）.The ratios of relative areas of the bands of amide Ⅱ, lignin, and amide I were 38.86%, 28.68% and 32.47% in the spectra of healthy leaves, respec-tively. It was distinguished from the diseased leaves （chocolate spot leaf： 15.42%, 42.98% and 41.61%, ring spot leaf：32.39%, 35.63% and 31.98%, rust leaf： 13.97%, 46.40% and 39.65%, yel owing leaf curl disease leaf： 24.01%,36.55% and 39.44%）. For sub-peak area ratios （A1 563/A1 605, A1 650/A1 605 and A1 563/A1 654）, those of four kinds of diseased leaves were smal er than that of healthy leaves, and there were also differences among four kinds of diseased leaves. The results proved that FTIR combining with curve fitting might be a potential y useful tool for detecting different kinds of broad bean diseases.

Mid-infrared Optical Frequency Comb-based Fourier Transform Spectrometer for Broadband Molecular Spectroscopy

Optical frequency combbased Fourier transform spectroscopy has the features of broad spectral bandwidth,high sensitivity,andmultiplexed trace gas detection,which has valuable application potential in the fields of precision spectroscopy and trace gas detection.Here,we report the development of a mid-infrared Fourier transform spectrometer based on an optical frequency comb combined with a Herriott-type multipass cell.Using this instrument,the broadband absorption spectra of several important molecules,including methane,acetylene,water molecules and nitrous oxide,are measured by near real-time data acquisition in the 2800-3500 cm^(-1)spectral region.The achieved minimum detectable absorption of the instrument is 4.4×10^(-8)cm^(-1)·Hz^(-1/2)per spectral element.Broadband spectra of H_(2)0 are fited using the Voigt profile multispectral fitting technique and the consistency of the concentration inversion is 1%.Our system also enables precise spectroscopic measurements,and it allows the determination of the spectral line positions and upper state constants of N_(2)O in the(0002)-(1000)band,with results in good agreement with those reported by Toth[Appl.Opt.30,5289(1991)].

Effect of the nonlinearity of the CCD in Fourier transform profilometry on spectrum overlapping and measurement accuracy

In Fourier transform profilometry （FTP）, we must restrain spectrum overlapping caused by the nonlinearity of the charge coupled device （CCD） and increase the measurement accuracy of the object shape. Firstly, the causes of producing higher-order spectrum components and inducing spectrum overlapping are analysed theoretically, and a simple physical ex- planation and analytical deduction are given. Secondly, aiming to suppress spectrum overlapping and improve measurement accuracy, the influence of spatial carrier frequency of projection grating on them is analysed. A method of increasing the spatial carrier frequency of projection grating to restrain or reduce the spectrum overlapping significantly is proposed. We then analyze the mechanism of how the spectrum overlapping is reduced. Finally, the simulation results and experimental measurements verify the correction of the proposed theory and method.

On Choosing Fourier Transforms for Practical Geoscience Applications

The variety of definitions of Fourier transforms can create confusion for practical applications. This paper examines the choice of formulas for Fourier transforms and determines the appropriate choices for geoscience applications. One set of Discrete Fourier Transforms can be defined that approximate Fourier integrals and provide transforms between sampled continuous functions in both domains. For applications involving transforms between a continuous function and a discrete function a second set of Discrete Fourier Transforms is needed with different scaling factors. Two classes of application are presented: those where either form of transforms can be used and those where it is necessary to use a particular transform to obtain the correct results.

FOURIER变换在脑电信号处理中的应用及其局限

介绍了Fourier变换在脑电信号处理中的应用，分析了Fourier变换存在的局限，指出了解决的途径．

Characteristic wavelength selection of volatile organic compounds infrared spectra based on improved interval partial least squares

As important components of air pollutant,volatile organic compounds(VOCs)can cause great harm to environment and human body.The concentration change of VOCs should be focused on in real-time environment monitoring system.In order to solve the problem of wavelength redundancy in full spectrum partial least squares(PLS)modeling for VOCs concentration analysis,a new method based on improved interval PLS(iPLS)integrated with Monte-Carlo sampling,called iPLS-MC method,was proposed to select optimal characteristic wavelengths of VOCs spectra.This method uses iPLS modeling to preselect the characteristic wavebands of the spectra and generates random wavelength combinations from the selected wavebands by Monte-Carlo sampling.The wavelength combination with the best prediction result in regression model is selected as the characteristic wavelengths of the spectrum.Different wavelength selection methods were built,respectively,on Fourier transform infrared(FTIR)spectra of ethylene and ethanol gas at different concentrations obtained in the laboratory.When the interval number of iPLS model is set to 30 and the Monte-Carlo sampling runs 1000 times,the characteristic wavelengths selected by iPLS-MC method can reduce from 8916 to 10,which occupies only 0.22%of the full spectrum wavelengths.While the RMSECV and correlation coefficient(Rc)for ethylene are 0.2977 and 0.9999 ppm,and those for ethanol gas are 0.2977 ppm and 0.9999.The experimental results show that the iPLS-MC method can select the optimal characteristic wavelengths of VOCs FTIR spectra stably and effectively,and the prediction performance of the regression model can be significantly improved and simplified by using characteristic wavelengths.

The quantum spectra analysis of the circular billiards in wells

We use a recently defined quantum spectral function and apply the method of closed-orbit theory to the 2D circular billiard system. The quantum spectra contain rich information of all classical orbits connecting two arbitrary points in the well. We study the correspondence between quantum spectra and classical orbits in the circular, 1/2 circular and 1/4 circular wells using the analytic and numerical methods. We find that the peak positions in the Fourier- transformed quantum spectra match accurately with the lengths of the classical orbits. These examples show evidently that semi-classlcal method provides a bridge between quantum and classical mechanics.

The quantum spectral analysis of the two-dimensional annular billiard system

Based on the extended closed-orbit theory together with spectral analysis, this paper studies the correspondence between quantum mechanics and the classical counterpart in a two-dimensional annular billiard. The results demonstrate that the Fourier-transformed quantum spectra are in very good accordance with the lengths of the classical ballistic trajectories, whereas spectral strength is intimately associated with the shapes of possible open orbits connecting arbitrary two points in the annular cavity. This approach facilitates an intuitive understanding of basic quantum features such as quantum interference, locations of the wavefunctions, and allows quantitative calculations in the range of high energies, where full quantum calculations may become impractical in general. This treatment provides a thread to explore the properties of microjunction transport and even quantum chaos under the much more general system.

Power and Cross-Spectra for the Turbulent Atmospheric Motion and Transports in the Domain of Wave Number Frequency Space: Theoretical Aspects

The study of large-scale atmospheric turbulence and transport processes is of vital importance in the general circulation of the atmosphere. The governing equations of the power and cross-spectra for the atmospheric motion and transports in the domain of wave number frequency space have been derived. The contributions of the nonlinear interactions of the atmospheric waves in velocity and temperature fields to the conversion of kinetic and potential energies and to the meridional transports of angular momentum and sensible heat in the atmosphere have been discussed.

应用衰减全反射红外光谱无损鉴别中国传统手工纸的方法研究

纤维种类鉴别是古代纸张保护的重要基础工作。探究中国传统手工纸的无损纤维鉴别的方法对中国古籍、档案及纸质文物的研究和保护具有重要意义。该研究应用衰减全反射傅里叶变换红外光谱(ATRFTIR)对已知纤维成分的17类64种中国传统手工纸标准样品进行了无损分析,参考纤维素和木质素的红外峰位及部分纸样的X射线衍射(XRD)分析结果确认纸样中的所有红外谱峰归属;并采用分波段比较分析的方法对相似度极高的谱图进行比对分析,分别总结各类纸张在4000~1800、1800~1500、1500~1200和1200~600cm^(-1)四个波段的谱图特征;同时对4cm^(-1)精度的谱图进行二阶导数处理,分别总结各类纸张在1500~1200和1200~900cm^(-1)两个波段的二阶导数谱图特征;最后通过红外结晶指数及其他峰高和峰面积比值计算结果实现对纸类更细致的区分。应用上述方法对16个盲测样品进行了有效性测试,红外分析结果与显微纤维鉴别结果一致,初步证明了该方法在中国传统手工纸无损纤维鉴别上的可行性和有效性。实验结果表明,应用ATR-FTIR无损分析法可对麻、桑构皮、檀皮、瑞香皮和竹几大类原料的传统手工纸纤维类型作出快速而准确的鉴别,对于混料的宣纸也同样适用;但对于显微分析也难以鉴别的亲缘关系较近的植物原料如桑、构皮之间的精细鉴别仍有一定局限性。

常压下酸催化多元醇液化纤维素反应机理的研究

开发农林废弃物高值化利用路径与“深入推进能源绿色低碳转型”国家重大战略需求高度契合。实验探索农业废弃物玉米秸秆中纤维素组分常压酸(H3PO4)催化多元醇[丙二醇(PG)与二甘醇(DEG)混合液]液化反应路径为研究目标,了解酸催化多元醇作用条件下的木质生物质液化反应机理。采用傅里叶红外光谱(FTIR)、凝胶渗透色谱(GPC)、核磁共振波谱(NMR)及热重分析(TGA)对不同反应时间下纤维素液化所得生物油的化学基团、分子量及其分布、分子结构、热解等进行了分析。FTIR检测表明,不同反应时间所得生物油具有相似FTIR特征;液化初期,纤维素降解生成了较多的烃类、醚类和含羰基化合物;液化后期,纤维素中的糖类降解产物、羟基或烯烃与PG/DEG反应生成了难溶于1,4-二氧六环的有机物。GPC分析表明,随着液化的进行,纤维素分子链发生断裂程度加剧,降解生成低分子量(LMW)物质越来越多,降解反应占主导地位;而当反应时间达到某一值时,其降解产物与PG/DEG发生聚合反应产生越来越多的大分子量物质,使生物油的分子量不再降低,即聚合反应占主导地位。^(1)H-和^(13)C-NMR表明,纤维素在液化作用下发生降解使得分子链断裂,仍保留了部分葡萄糖单元结构;随着液化反应的进行,这些结构单元再次发生转化产生LMW化合物;反应继续进行时,这些产物之间或与PG/DEG之间可进行聚合反应,形成结构趋于一致、性质逐渐稳定的新物质。TGA分析结果:生物油中含有70%~85%碳数小于25和5%~10%碳数高于25的化合物,最终残炭率随着反应时间的延长先降低再升高。实验通过研究纤维素在多元醇液化过程中的结构变化,揭示其液化的反应历程,为探索秸秆全组分的液化机理奠定理论基础。

宁夏煤的分子结构演化特征

以宁夏宁东、贺兰山、宁南和香山等四大煤田不同矿区典型煤样为研究对象,采用X射线衍射、拉曼光谱和傅里叶红外光谱对煤结构进行表征,结合分峰拟合来获取煤结构参数及变化规律。结果表明:低-中煤阶煤光学性质是各向同性的,芳香层片尺寸较小,任意取向;随着煤级的增加,芳香层间距d002值以最快的速率减小,延展度La则加快增长,在Rmax大于2.0%后,d002值变化幅度减缓与堆砌度Lc值增大相对应;在d002<0.3480 nm,拉曼参数ID1/IG、AD1/AD1+G开始线性减小,煤的分子结构中芳香层片尺寸增大,定向性增强,光学性质在平行和垂直于芳香层片方向上呈现各向异性,结构有序化程度增大;随着煤化程度的增高,红外光谱显示脂肪结构含量较低,芳香结构吸收带显著,芳香度参数迅速增大,脂肪烃侧链快速脱落,生烃潜力参数‘A’变小;贺兰山煤田和香山煤田煤叠加了岩浆热作用,变质温度较高,导致芳香环缩合程度增强,芳香烃类物质增多。研究结果对煤的结构演化与煤炭清洁高效利用有一定指导意义。

Fourier Transformed Infrared Spectra of the Unfolding of Ribonuclease A in Guanidinium Chloride

The unfolding of proteins during denaturation by guanidine or urea has been extensively studied. However, the methods hitherto employed usually provide only a limited amount of information on gross changes of such molecular properties as shape, size, or the exposure of buried aromatic residues. CD studies are hampered by high absorption of the denaturants commonly employed in the far ultraviolet region. Recent development in Fourier

FOURIER TRANSFORM FAR INFRARED SPECTRA AND NORMAL COORDINATE ANALYSIS OF FIFTEEN RARE-EARTH OXALATE HYDRATES

The Fourier transform far infrared spectra of oxalate hydrates of whole rare-earth series except Pm and Sc are investigated in the range of 100-400 cm^(-1). The assignment of vibrational frequencies is made on the basis of normal coordinate analysis using our NORVIB program. The model used for the hghter elements of the lanthanide series (La to Eu) is based on the crystal structure of Nd_2(C_2O_4)_3. 10H_2O, in which each lanthanide ion is surrounded by nine O atoms, six from three oxalate ions and three from Water molecules.The model adopted for the heavier elements of the lanthanide series (Gd to Lu) and Ytterbium is based on the crystal structure of Yb_2(C_2O_4)_3· 6H_2O, in which each ion is surrounded by eight atoms, six from three oxalate ions and two from water molecules. The variation of the metal-ligand frequencies and force constants with the atomic numbers of lanthanides is plotted and discussed.

(2+1)维光折变波导阵列的制作

对四个点光源进行光学傅里叶变换 ,在自散焦光折变晶体中成功地制作了 6μm× 6μm间隔的并行 ( 2 + 1 )维阵列波导 30 0余条 ,并证明了阵列波导实质上是二维体相位栅 实验研究了点光源间距、点光源尺寸及写入时间对阵列波导制作的影响 。

FT-NIR光谱法测定紫花苜蓿青干草的6项品质指标

紫花苜蓿青干草营养价值非常高,能够为家畜提供大量优质的蛋白质饲料,也是目前我国最主要的草产品类型之一。文章应用傅里叶变换近红外（FT-NIR）光谱技术,使用偏最小二乘法首次建立了国内紫花苜蓿青干草粗蛋白、粗灰分、中性洗涤纤维、酸性洗涤纤维和酸性洗涤木质素以及体外干物质消化率等6项品质指标的预测模型,并对模型进行了交互验证和外部验证。结果表明：该试验所建立的紫花苜蓿青干草6项主要品质指标的近红外模型具有良好的准确性和预测能力,交互验证相关系数rval为0.953 88~0.990 19,交互验证均方根RMSECV分别为0.345%~1.980%,外部验证的相关系数为0.963~0.990。该方法快速、准确,无需化学试剂,对我国紫花苜蓿草产品的质量检测,以及科研中紫花苜蓿草产品品质分析、种质资源评价、育种世代的鉴定和筛选都有非常重要的意义。

花青素对大豆蛋白质二级结构影响的多重光谱分析

以大豆分离蛋白-花青素复合体系为研究对象,综合利用多重光谱技术对其进行分析。利用荧光光谱探究大豆分离蛋白和花青素间的相互作用方式,采用同步荧光光谱和紫外-可见光谱探究花青素对大豆分离蛋白氨基酸残基微环境的影响,从而得出花青素对大豆分离蛋白构象的影响,再采用傅里叶变换红外光谱法和圆二色谱法研究花青素对大豆分离蛋白二级结构的影响。结果表明:花青素对大豆分离蛋白有较强的荧光猝灭作用且为静态猝灭,其中,花青素与大豆分离蛋白在298、306、314 K时相互作用的表观结合常数分别为3.343×104、4.507×104、5.525×104L/mol,对应的结合位点数分别为0.917 8、0.954 6、0.938 1。热力学数据分析结果表明:花青素与大豆分离蛋白反应的作用力主要是疏水相互作用;同步荧光光谱和紫外-可见光谱结果表明花青素改变了芳香氨基酸残基在空间结构中所处的微环境,使大豆分离蛋白的分子构象发生改变,且同步荧光光谱显示花青素与大豆分离蛋白中色氨酸残基发生相互作用,使其周围的疏水作用减少。傅里叶变换红外光谱和圆二色谱结果表明花青素引起大豆分离蛋白的二级结构发生改变。

苹果硬度的傅里叶变换近红外光谱无损检测

利用傅里叶变换近红外光谱技术探讨快速无损检测苹果硬度方法的可行性。通过解析苹果样品的近红外光谱图,用一阶导数、多元散射校正和矢量归一等方法进行预处理,再用偏最小二乘法建立模型。结果表明,多元散射校正能够有效消除光谱基线平移和偏移现象,提高原光谱的信噪比,选取有效信息波长范围为1 408~2 355 nm。偏最小二乘法结合多元散射校正所建模型的预测效果最好,模型的决定系数R2为0.985 2,内部交叉验证均方根差RMSECV和预测标准偏差RMSEP分别为0.039 8 kg/cm2和0.016 6 kg/cm2。进一步通过剔除异常值优化模型,并验证检验组的25个样品,模型的R2为0.990 8,RMSEP为0.014 7 kg/cm2。结果表明：建立的模型可靠,预测效果好,能满足苹果硬度快速检测的要求。

优化Savitzky-Golay滤波器的参数及其在傅里叶变换红外气体光谱数据平滑预处理中的应用

对傅里叶变换中红外光谱数据的平滑预处理中,通常采用Savitzky-Golay滤波器的方法进行光谱数据的平滑预处理,然而Savitzky-Golay滤波器的多项式拟合阶次和窗宽等参数的合理选则始终是一个难题,并无统一的选择依据,通常在一定数值范围内,采用多组数据进行遍历尝试,最终选择一组相对较优的数据作为Savitzky-Golay滤波器的多项式拟合阶次和窗宽参数。文中探索了Savitzky-Golay滤波器的多项式拟合阶次和窗宽等参数的优化选取这一问题,并对其主要频率指标参数与多项式拟合阶次和窗宽等参数进行了定性定量分析,得出了截至频率、阻带起始点频率、第一旁瓣峰值频率及第一旁瓣峰值幅度与窗宽和阶次之间具体的计算方程表达式。随后,根据采集的中红外气体组分的光谱数据特征,依据上述计算方程式,优化计算选取多项式拟合阶次和窗宽分别为8和11时,其Savitzky-Golay滤波器的中红外气体组分的光谱数据平滑效果最优。最后通过实际采集的0.1%,0.2%,0.5%,1%,2%,5%浓度的CH_4光谱数据进行平滑预处理,在次吸收峰区域,原始光谱的折算吸光率相对最大误差和最小误差分别为17.230 5%和0.243 0%,平滑处理后的光谱的折算吸光率相对最大误差和最小误差分别为0.088 0%和0.020 6%。可见经过Savitzky-Golay滤波器进行所探索的光谱数据预处理之后其相对误差基本稳定,并且相对较低,为后期光谱数据的准确定性和定量分析奠定了基础。