Rapid prediction of past climate condition from lake sediments by near-infrared (NIR) spectroscopy

This study explored the feasibility of rapid, nondestructive near-infrared (NIR) reflection spectroscopy for the prediction of conventional physical properties, carbon-nitrogen-sulfur (CNS) analysis, and concentration of inorganic components in sediment cores from a brackish lake. A long core sample, which consisted of well-preserved annually formed lamina from Lake Ogawara along the Pacific coast in Aomori Prefecture, northeastern Japan, was used to investigate the past environmental record. The core was previously analyzed for physical properties, CNS, and inorganic components. Calibration models were developed from NIR reflection spectra of 149 core samples. Partial least squares (PLS) analysis provided good regression models between measured and predicted values for water content, total nitrogen (TN), total organic carbon (TOC), total sulfur (TS), Al(2)O(3), S/Al(2)O(3), Fe(2)O(3)/Al(2)O(3), Sc/Al(2)O(3), Cu/Al(2)O(3), and Zn/Al(2)O(3) with coefficients of determination (r(2)) for cross-validation of 0.73, 0.89, 0.88, 0.73, 0.92, 0.81, 0.82, 0.75, 0.82, and 0.82, respectively. The variation of predicted component values as a function of depth showed the same trend as that of conventionally measured values. This study also showed the possibility of NIR spectroscopy as an on-site, rapid analytical tool for the identification of tephra (fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism), which is important for dating.     

近红外光谱技术对滤棒中三醋酸甘油酯含量快速测定的研究

本文将卷烟滤棒的近红外光谱图与相应的三醋酸甘油酯含量进行关联,采用偏最小二乘法建立近红外光谱图与卷烟滤棒中三醋酸甘油酯含量间的数学校正模型,使用校正模型不需对样品进行前处理,并与CORESTA推荐方法测得的结果无显著性差异。该方法过程简单、快速,结果令人满意,适用于成型车间批量检测样品的需求。     

烟丝掺配均匀性的近红外光谱识别

烟丝掺配过程是否均匀直接影响到卷烟产品质量。本文利用近红外光谱技术建立了膨胀烟丝、梗丝、大线烟丝、小线烟丝掺配分析的识别模型,结果表明:建立的模型能够准确预测出烟丝配方中膨胀烟丝、梗丝、大线烟丝、小线烟丝的掺配比例,并且模型的相关系数在0.95以上,预测相对偏差在3.5%以下。该方法操作简单,能够快速准确地表征出烟丝掺配的均匀性。     

Characterization and evaluation of wood strand composite load capacity with near infrared spectroscopy

This study looked at the ability to use near infrared reflectance spectroscopy to non-destructively assess the load capacity and deflection of oriented strand construction board in the presence of phenol formaldehyde (PF) resin variation. The influence of PF resin on both mechanical properties was significant. Principal components regression was used to determine and rank statistically important principal components. For prediction of load capacity, the following associated wavelengths were important and in the following order: urea > lignin > cellulose > PF. Likewise, for prediction of deflection within the elastic region, the following associated wavelengths were important: urea > cellulose > lignin > PF. Models for prediction of load capacity (R ² = 0.69) were stronger than those for deflection (R ² = 0.59). It was determined that the predictive capability of the multivariate models were strong enough to characterize population parameters and for interpretation purposes but may not be precise enough for the accurate screening of individual panels.     

In-line monitoring of the thickness of printed layers by near-infrared (NIR) spectroscopy at a printing press

In this work, it is demonstrated that the coating weight of printed layers can be determined in-line in a running printing press by near-infrared (NIR) reflection spectroscopy assisted by chemometric methods. Three different unpigmented lacquer systems, i.e., a conventional oil-based printing lacquer, an ultraviolet (UV)-curable formulation, and a water-based dispersion varnish, were printed on paper with coating weights between about 0.5 and 7 g m(-2). NIR spectra for calibration were recorded with a special metal reflector simulating the mounting conditions of the probe head at the printing press. Calibration models were developed on the basis of the partial least squares (PLS) algorithm and evaluated by independent test samples. The prediction performance of the developed models was examined at a sheet-fed offset printing press at line speeds between 90 and 180 m min(-1). Results show an excellent correlation of data predicted in-line from the NIR spectra with reference values obtained off-line by gravimetry. The prediction errors were found to be ≤ 0.2 g m(-2), which confirms the suitability of the developed spectroscopic method for process control in technical printing processes.     

Near-infrared (NIR) Raman spectroscopy of Precambrian carbonate stromatolites with post-depositional organic inclusions

Raman spectroscopy has promising potential for future Mars missions as a non-contact detection technique for characterizing organic material and mineralogy. Such a capability will be useful for selecting samples for detailed analysis on a rover and for selecting samples for return to Earth. Stromatolites are important evidence for the earliest life on Earth and are promising targets for Mars investigations. Although constructed by microorganisms, stromatolites are organo-sedimentary structures that can be large enough to be discovered and investigated by a Mars rover. In this paper, we report the Raman spectroscopic investigations of the carbonate mineralogy and organic layering in a Precambrian (~1.5 Gyr old) stromatolite from the Crystal Spring Formation of Southern California. Ultraviolet (UV: 266 nm), visible (514 nm, 633 nm), and near-infrared (NIR: 785 nm, 1064 nm) Raman spectra are presented. We conclude that 1064 nm excitation is the optimal excitation wavelength for avoiding intrinsic fluorescence and detecting organic carbon within the carbonate matrix. Our results confirm that NIR Raman spectroscopy has important applications for future Mars missions.     

Measurement of strain distributions near the steel/epoxy interface by micro-Raman spectroscopy under tensile load condition

Micro-Raman spectroscopy was applied for evaluating the stress distributions in the vicinity of the interface of the steel/epoxy bonded joint under tensile loading condition. Herein, single-walled carbon nanotubes (SWNTs) embedded in a polymer can be used as a mechanical sensor, in which the position of the D* Raman band varies with the strain or stress transferred to SWNTs from the surrounding matrix. In order to evaluate the strain distributions, however, it is required to elucidate the effect of the multiaxial stress on the D* band shift, because a multiaxial stress field appears in the vicinity of the interface and, the validity of this method has been confirmed only under uniaxial loading condition. Hence, at first, the D* band shift of a bulk epoxy/SWNT composite was measured under biaxial loading condition using a cruciform-type specimen. It was found that the D* band shift could be standardized in terms of the strain in the polarized direction even though under the biaxial condition. Then, on the basis of the result, this method was applied for evaluating the strain distributions of the steel/SWNT composite bonded joints under uniaxial tensile loading condition. The observation indicated that the strain singularity appeared in the vicinity of the interface, similar to the results of the finite-element analysis, and the observed strain almost agreed with calculated one in the range of 0.03–10 mm distance from the interface.     

Surface analysis of different wood species using X-ray photoelectron spectroscopy (XPS)

X-ray photoelectron spectroscopy (XPS) was used to characterize the surfaces of mechanically treated wood. Microtomed and sanded surfaces of spruce, larch, beech and oak were investigated. Changes due to the sanding process were identified from the survey spectra as well as from the detailed C1s spectra. The changes were quantified with the atomic ratio of oxygen to carbon and with a detailed analysis of the contributions to the C1s peak. The identified changes were explained in terms of the macromolecular wood substances and in terms of density and the amount of extractives.     

Near Infrared 45°/0° Reflectance Factor of Pressed Polytetrafluoroethylene (PTFE) Powder

Pressed polytetrafluoroethylene (PTFE) powder is commonly used as a reflectance standard for bidirectional and hemispherical geometries. The wavelength dependence of the reflectance factor of PTFE is presented for the near-infrared spectral region (800 nm to 1600 nm) for the 45°/0° geometry, as well as in the visible spectral region (380 nm to 800 nm) for comparison with previously published results.     

Time-resolved optical spectroscopy of wood

We have proposed and experimentally demonstrated that picosecond time-resolved optical spectroscopy in the visible/near-infrared (NIR) region (700-1040 nm) is a useful technique for noninvasive characterization of wood. This technique has been demonstrated on both softwood and hardwood samples treated in different ways simulating the aging process suffered by waterlogged woods. In all the cases, alterations of absorption and scattering spectra were observed, revealing changes of chemical and structural composition.     

Near infrared absorption coefficient of molten glass by emission spectroscopy

Emission spectroscopy is applied in the determination of the near infrared spectral absorption coefficient of molten glass. The glass is held in a small horizontal platinum alloy crucible, within an electrically heated cell, optically coupled to a Fourier transform spectrometer. A formula is derived which relates emissivity to absorption coefficient, thickness, and reflectivities for the glass-air and glass-metal interfaces. The reflectivity parameters are determined, in effect, by varying the thickness. Spectral absorption coefficient results are compared with results of transmission spectroscopy. The emission technique is advantageous in that it eliminates the problem of chemical reactions with window materials used in the transmission method, and sample preparation and interfacing to commercially available spectrometers is simplified.     

Infrared spectroscopy of double-four-ring silicates

Attenuated—total—reflection infrared spectroscopy has been applied to characterize tetramethylammonium double-four-ring silicates in solution as well as in hydrate crystals. It is shown that tetramethylammonium silicate solutions at elevated temperatures (up to 85°C) still contain significant concentrations of double-four-ring silicate anions. Furthermore, the temperature-dependent shift in equilibrium between silicate anions appears to be fully reversible. A relation to the role of silicate anions in zeolite syntheses is suggested.     

Infrared spectroscopy of a silicon surface bombarded by nitrogen ions

Transmission Fourier-transform infrared spectroscopy was used to study the formation of a ripple topology on a silicon surface bombarded by nitrogen ions, together with the formation of silicon nitride, the evolution of its composition and structure. For the first time, an attempt is made to study the evolution of the formation of a ripple topology on the surface of silicon by analyzing the main spectral characteristics (amplitude, position, and profile) of the infrared absorption bands. It is shown that the change in the profile of the characteristic absorption band and the position of its peak correlate with the characteristics of formation of the ripples on the silicon surface. It is demonstrated that infrared transmission spectroscopy can be used to study surface structuring processes for semiconductors bombarded by ions of chemically active elements. Pis’ma Zh. Tekh. Fiz. 24, 18–23 (March 26, 1998)     

近红外漫反射光谱逐步回归分析测定饲料中水份含量

本文用近红外漫反射光谱逐步回归法测定了饲料的水份含量,预测结果的平均相对误差为3.8%。该法具有方便、快速、无损、不需化学前处理等优点,特别适用于大批量样品的分析和在线监控。     

Radiometric Measurement Comparison Using the Ocean Color Temperature Scanner (OCTS) Visible and Near Infrared Integrating Sphere

As a part of the pre-flight calibration and validation activities for the Ocean Color and Temperature Scanner (OCTS) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color satellite instruments, a radiometric measurement comparison was held in February 1995 at the NEC Corporation in Yokohama, Japan. Researchers from the National Institute of Standards and Technology (NIST), the National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC), the University of Arizona Optical Sciences Center (UA), and the National Research Laboratory of Metrology (NRLM) in Tsukuba, Japan used their portable radiometers to measure the spectral radiance of the OCTS visible and near-infrared integrating sphere at four radiance levels. These four levels corresponded to the configuration of the OCTS integrating sphere when the calibration coefficients for five of the eight spectral channels, or bands, of the OCTS instrument were determined. The measurements of the four radiometers differed by −2.7 % to 3.9 % when compared to the NEC calibration of the sphere and the overall agreement was within the combined measurement uncertainties. A comparison of the measurements from the participating radiometers also resulted in agreement within the combined measurement uncertainties. These results are encouraging and demonstrate the utility of comparisons using laboratory calibration integrating sphere sources. Other comparisons will focus on instruments that are scheduled for spacecraft in the NASA study of climate change, the Earth Observing System (EOS).     

Accelerated weathering-induced degradation of poly(lactic acid) fiber studied by near-infrared (NIR) hyperspectral imaging

Hydrolysis degradation of a set of drawn poly(lactic acid) (PLA) fibers was induced by an accelerated weathering test, radiating ultraviolet (UV) light under a certain temperature and humidity. The fine features of the transient behavior of the PLA fibers were captured by near-infrared (NIR) hyperspectral imaging. The PLA fibers showed a gradual decrease in mechanical property (e.g., tensile strength), indicating hydrolysis degradation. Thus, the detailed analysis of the spectral variation, in turn, offers useful information on the molecular-level degradation behavior of the drawn PLA fibers. The variation of the spectral intensity as well as band position shift of the crystalline band of PLA was analyzed. The spectral intensity of the crystalline band of PLA showed gradual decrease, suggesting the decrease in molecular weight induced by the hydrolysis degradation. In addition, the crystalline band also exhibited a coinciding shift to the lower wavenumber direction with the weathering test, revealing cleavage-induced crystallization of the PLA samples. Consequently, the hydrolysis degradation induced by the weathering test substantially accelerates predominant degradation of the amorphous structure of the PLA and such variation of the molecular structure, in turn, brings less ductility to the PLA fiber.     

Infrared spectroscopy of fluid lipid bilayers

Infrared spectroscopy is a powerful technique for examining lipid bilayers; however, it says little about the fluidity of the bilayer-a key physical aspect. It is shown here that it is possible to both acquire spectroscopic data of supported lipid bilayer samples and make measurements of the membrane fluidity. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FT-IR) is used to obtain the spectroscopic information and fluorescence recovery after photobleaching (FRAP) is used to determine the fluidity of the samples. In the infrared spectra of lipid bilayers composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, the following major peaks were observed; nu(as)(CH3) 2954 cm(-1), nu(s)(CH3) 2870 cm(-1), nu(as)(CH2) 2924 cm(-1), nu(s)(CH2) 2852 cm(-1), nu(C=O) 1734 cm(-1), delta(CH2) 1463-1473 cm(-1), nu(as)(PO2-) 1226 cm(-1), nu(s)(PO2-) 1084 cm(-1), and nu(as)(N+(CH3)3) 973 cm(-1). The diffusion coefficient of the same lipid bilayer was measured to be 3.5 +/- 0.5 micom(2)/s with visual recovery also noted through use of epifluorescence microscopy. FRAP and visual data confirm the formation of a uniform, mobile supported lipid bilayer. The combination of ATR-FT-IR and FRAP provides complementary data giving a more complete picture of fully hydrated model membrane systems.     

Comparison of linear and nonlinear calibration models based on near infrared (NIR) spectroscopy data for gasoline properties prediction

Six popular approaches of «NIR spectrum–property» calibration model building are compared in this work on the basis of a gasoline spectral data. These approaches are: multiple linear regression (MLR), principal component regression (PCR), linear partial least squares regression (PLS), polynomial partial least squares regression (Poly-PLS), spline partial least squares regression (Spline-PLS) and artificial neural networks (ANN). The best preprocessing technique is found for each method. Optimal calibration parameters (number of principal components, ANN structure, etc.) are also found. Accuracy, computational complexity and application simplicity of different methods are compared on an example of prediction of six important gasoline properties (density and fractional composition). Errors of calibration using different approaches are found. An advantage of neural network approach to solution of «NIR spectrum–gasoline property» problem is illustrated. An effective model for gasoline properties prediction based on NIR data is built.