bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Cereal Quality by Micro-Raman Analysis of the Grain Molecular Composition
Authors: Piot Olivier , Autran Jean Claude , Manfait Michel
Published: October 2003

The development of confocal Raman microspectroscopy for cereal grain studies has led to breakthroughs in the understanding of the molecular basis of grain texture. The high spatial resolution and the nondestructive nature of the technique are its main assets, enabling more detailed analysis of the microscopic structure of wheat grain and investigation of the role of specific components involved in hardness. Hardness is the most relevant criterion in determining the suitability of wheat grain to be processed into flour. Our findings indicate that the α-helical secondary structure of protein could be associated with hardness.
Noninvasive Assay for Cyanogenic Constituents in Plants by Raman Spectroscopy: Content and Distribution of Amygdalin in Bitter Almond (Prunus Amygdalus)
Authors: Micklander E. , Brimer L. , Engelsen S. B.
Published: October 2003

The ability of Fourier transform Raman spectroscopy to measure cyanogenic glycoside amygdalin was investigated using a standard addition series in which amygdalin (0–700 nmol/mg) was added to ground sweet almond. As an additional test, the method so developed, and further refined, was used to determine endogenous amygdalin in bitter almonds. Using partial least-squares regression (PLSR), the best correlation between the spectra of the standard addition series and amygdalin content exhibited a value of 0.999, while the root mean square error of cross validation (RMSECV) was found to be 4 nmol/mg using one principal component. The model was based on the first derivative of the aromatic C–H stretching band at 3060 cm−1. A less accurate but still excellent PLSR model could be developed on the vibrational band of the nitrile group, specific for the cyanogenic compound in the system. The best PLSR model obtained for endogenous amygdalin in 17 raw bitter almonds yielded a RMSECV = 13 nmol/mg and r = 0.937. In addition, the distribution of amygdalin in bitter almond was investigated in situ by obtaining spectra of an intact cross-section of the cotyledon of bitter almond using Raman microscopy. While amygdalin was found not to be present in measurable amounts in the center of bitter almond, the concentration increased towards the epidermis, but not linearly.
Determination of Cyanide Species in Silver and Gold Plating Solutions by Raman Spectroscopy
Authors: Cho Keunchang , Jang Yong Soon , Gong Myoung-Seon , Kim Kwan , Joo Sang-Woo
Published: October 2003

Raman spectra of silver and gold cyanide complexes have been investigated in order to determine the speciation of aqueous plating solutions. We have examined the ionic species in the concentration ranges of 0.003 ∼ 0.5 M for the metals and 0.1 ∼ 2.5 M for the cyanide ion. When the initial concentration of [Ag(CN)2]− was below ∼0.1 M, [Ag(CN)4]3– did not appear prominent even at high CN−/Ag(I) ratios of 3 ∼ 10, differing from the case of previous infrared measurements. Concentrations of the metal cyanide complexes and CN− ion as low as 0.001 ∼ 0.01 M could be determined with an error of less than ∼3% from the analysis of Raman peak areas.
Elemental Analysis of Stainless Steel Using Hard X-Ray Emission Arising from a High-Density Plasma Produced by an Intense Femtosecond KrF Laser Pulse
Authors: Takeyasu N. , Hirakawa Y. , Imasaka T.
Published: October 2003

Characteristic hard X-rays emitted from a laser-produced plasma induced by focusing a femtosecond KrF laser pulse are employed for elemental analysis. The emission spectrum of the hard X-ray arising from a stainless steel sample is measured by means of a single-photon-counting X-ray detector equipped with a multichannel analyzer. The elemental analysis is carried out from the photon energy of the Kα line observed in the X-ray emission spectrum, and a calibration curve is constructed for Fe using stainless steel samples prepared at different concentrations (SUS-301, 310, and 316). A continuum band was overlapped on the sharp Kα lines in the X-ray spectrum, which made the assignment of the weak characteristic Kα lines arising from minor elements difficult. In order to suppress this undesirable emission, a prepulse technique was employed. The continuum emission was shifted toward lower energies, and, as a result, the characteristic Kα lines were more clearly observable. The potential advantages of the present approach are also discussed in this study.
Emission Characteristics of a Low-Pressure Laser-Induced Plasma: Selective Excitation of Ionic Emission Lines of Copper
Authors: Matsuta Hideyuki , Wagatsuma Kazuaki
Published: October 2003

Under reduced pressures, the plasmas produced by irradiation of a Q-switched Nd:YAG laser have favorable features as an excitation source for solid samples in atomic emission spectrometry, such as relatively low fluctuation of the emission intensity and a high signal-to-background ratio. For the analytical application of low-pressure laser-induced plasma spectroscopy (LP-LIPS), the spectra should be examined regarding the type of emission lines and their relative intensities. Further, information on the excitation mechanism in the plasma could be useful in determining optimum operation conditions of the experimental parameters. Spectrum patterns of LP-LIP are principally determined by the type of the filled gas. Especially, particular ionic lines of Cu are selectively excited when Ar or Ne are employed as the filled gas. This feature seems to be due to the (quasi-) resonance charge transfer collisions between a ground state ion of the Ar or Ne gas and a ground state atom of Cu. The plasma plume expanding after the laser irradiation also becomes an excitation source for sample atoms introduced by laser ablation.
Characterization of Waste Organic Matter by FT-IR Spectroscopy: Application in Waste Science
Authors: Smidt E. , Lechner P. , Schwanninger M. , Haberhauer G. , Gerzabek M. H.
Published: October 2003

A series of experiments has shown that FT-IR (Fourier transform infrared) spectroscopy is a helpful tool for characterizing waste organic matter, its decomposition, and stabilization in rotting processes. A specific set of differently treated input materials, originating from various composting plants, was chosen to reflect a wide range of spectroscopic properties. The approach to FT-IR spectra interpretation is presented. Changes of relative absorbances of the band at 2925 cm−1 (methylene groups of aliphatics) reflect the progress and dynamics of composting processes. Different processes can be compared by the specific development of their 2925 cm−1 band. Nitrate was quantified by calibrating nitrate band heights with added amounts of KNO3. The concentrations and band heights (absorbances) were linearly correlated ( R2 = 0.9968, SD = 0.001). Bands of inorganic components are useful to assess the decomposition process because they also indicate the development of organic matter. Different wastes can be distinguished by their fingerprint region (1500–900 cm−1). This region also reveals fresh and undecomposed materials. The presence or absence of specific bands provides information about the decomposition status of materials.
Stability and Disturbance of Fatty Acid Layers by Polymer in Lead Stearate/Poly(tert-Butyl Methacrylate) Alternating Langmuir—Blodgett Films
Authors: Shin Hyeon Suk , Cha Junhoe , Chang Taihyun , Kim Seung Bin
Published: October 2003

The stability of lead stearate layers in alternating Langmuir–Blodgett (LB) films of lead stearate/lead deuterated stearate with and without poly( tert-butyl methacrylate) (PtBMA) layers at each interface was measured from the magnitude of the splitting of the CH2 or CD2 scissoring band in transmission FT-IR spectra. Before annealing, the extent of splitting of the CH2 or CD2 bending mode in the alternating LB film with PtBMA layers was larger than that in the alternating LB film without PtBMA layers. However, the opposite trend was observed after annealing. This suggests that PtBMA does not function as a barrier to interlayer mixing on annealing. The results presented here represent the first report that PtBMA has two important roles: before annealing it stabilizes the fatty acid layers, and after annealing it disturbs these layers. PtBMA is expected to act as a substrate when it is inserted between fatty acid layers. This PtBMA substrate can stabilize the fatty acid layers at room temperature. However, external reflection FT-IR spectra indicate that annealing causes the reorientation of PtBMA. This reorientation of PtBMA could disturb the fatty acid layers.
Infrared Two-Dimensional Correlation and Principal Component Analyses Applied to β-Lactoglobulin Aggregation in Water—Ethanol Solution
Authors: Robert P. , Lavenant L. , Renard D.
Published: October 2003

Changes of the secondary structure of β-lactoglobulin in water–ethanol solutions were studied using infrared spectroscopy. The efficiency of both principal component analysis and two-dimensional correlation spectroscopy in avoiding spectral subtraction of water was evaluated. The kinetic curves assessed from the scores of the first principal component indicated that changes were more pronounced in 50% ethanol solution than in 5% ethanol–water solution. The spectral patterns derived from the eigenvectors made it possible to characterize changes in the secondary structure of the protein. While aggregation was obtained in 50% ethanol solution, α-helices were formed at the detriment of turns in 5% ethanol solution. The two-dimensional correlation spectroscopy provided information on the sequence of events that occurred by adding ethanol to aqueous solutions of β-lactoglobulin. In 5% ethanol solution, the disappearance of turns preceded the formation of α-helices. Moreover, a small amount of aggregates were depicted at the end of the process. Aggregation of the protein was the main event observed in 50% ethanol–water solution. This event was preceded by the disappearance of α-helices. Application of both principal component analysis and two-dimensional correlation spectroscopy to spectra recorded in H2O made it possible to detect small changes not observed on second derivative spectra collected in D2O.
Two-Dimensional Attenuated Total Reflection/Infrared Correlation Spectroscopy Studies on Concentration and Heat-Induced Structural Changes of Human Serum Albumin in Aqueous Solutions
Authors: Wu Yuqing , Murayama Koichi , Czarnik-Matusewicz Boguslawa , Ozaki Yukihiro
Published: October 2003

Attenuated total reflection (ATR)/FT-IR spectra were measured for human serum albumin (HSA) in aqueous solutions (pH 6.6) with concentrations of 1.0, 2.0, 3.0, 4.0, and 5.0 wt % over a temperature range of 45–80 °C. Generalized two-dimensional (2D) correlation spectroscopy was employed to explore concentration and heat-induced structural variations of HSA in aqueous solutions. To generate 2D correlation spectra, the raw spectra were subjected to the appropriate pretreatment procedure involving ATR correction, subtraction of the spectrum of an aqueous solution, and smoothing. The synchronous and asynchronous correlation spectra were calculated for the concentration-dependent IR spectral variations in the amide I region at various temperatures. The two-dimensional ATR/IR correlation spectra greatly enhance band separation in the region and provide information about the correlation between the amide bands of HSA arising from the same and different secondary structure components. Based on the correlation investigated and previously proposed relationship between the secondary structure elements and the amide band frequencies, we have proposed the detailed assignments in the amide I region at 45 and 80 °C. The proposed assignments are compared with those based on the results of second derivative and Fourier self-deconvolution (FSD) of the ATR/IR spectra. The asynchronous spectrum generated from the concentration-dependent spectral variations at 45 °C show that side chains, the random coil, and extended chains are more sensitive than the α-helices and β-turns to the concentration change. On the other hand, the corresponding spectrum at 80 °C reveals that the conformation changes in side chains and β-turns (or β-strands) of HSA start before those in extended chain, random coil structures, and α-helices.
Near-Infrared Absorption and Scattering Separated by Extended Inverted Signal Correction (EISC): Analysis of Near-Infrared Transmittance Spectra of Single Wheat Seeds
Authors: Pedersen Dorthe Kjær , Martens Harald , Nielsen Jesper Pram , Engelsen Søren Balling
Published: October 2003

A new extended method for separating, e.g., scattering from absorbance in spectroscopic measurements, extended inverted signal correction (EISC), is presented and compared to multiplicative signal correction (MSC) and existing modifications of this. EISC preprocessing is applied to near-infrared transmittance (NIT) spectra of single wheat kernels with the aim of improving the multivariate calibration for protein content by partial least-squares regression (PLSR). The primary justification of the EISC method is to facilitate removal of spectral artifacts and interferences that are uncorrelated to target analyte concentration. In this study, EISC is applied in a general form, including additive terms, multiplicative terms, wavelength dependency of the light scatter coefficient, and simple polynomial terms. It is compared to conventional MSC and derivative methods for spectral preprocessing. Performance of the EISC was found to be comparable to a more complex dual-transformation model obtained by first calculating the second derivative NIT spectra followed by MSC. The calibration model based on EISC preprocessing performed better than models based on the raw data, second derivatives, MSC, and MSC followed by second derivatives.
Detection of Mie Scattering Using a Resonance Fluorescence Monochromator
Authors: Pappas Dimitri , Correll Tiffany L. , Pixley Nathan C. , Smith Benjamin W. , Winefordner J. D.
Published: October 2003

The use of a resonance fluorescence monochromator (RFM) is described as a method for detecting Mie scatter. The detector has a spectral resolution limited by the atomic vapor used in the system (400 MHz for cesium). The RFM is used to detect Mie scatter from a particulate suspension, and deconvolution methods are used to extract the Mie scatter spectrum from the instrument response. The Mie scattering linewidth (140 MHz) is close to the literature value (100 MHz for air). Methods to reduce the linewidth of atomic vapor filters are briefly described.
Synchronicity and Linearity in Generalized Two-Dimensional Correlation Spectroscopy: Concepts Relevant to the Analysis of Nonperiodic, Monotonically Increasing or Decreasing Spectroscopic Signals
Authors: Isaksson T. , Katsumoto Y. , Ozaki Y. , Noda I.
Published: October 2003

The theory and terminology for two-dimensional (2D) infrared correlation spectroscopy were originally developed for the analysis of dynamic IR signals induced by periodic perturbations. The generalized 2D spectroscopy method defines synchronous and asynchronous relationships mathematically rigorously, both for periodic and nonperiodic perturbations. However, the concept of synchronicity may not be intuitively easy to understand when applying the generalized 2D spectroscopy method to the analysis of nonperiodic perturbations. We propose an alternative and novel measure and concept especially useful for nonperiodic perturbations. Our main proposal, when interpreting 2D maps, is to focus on linearity instead of synchronicity. We also propose a simple plot to reveal, verify, and identify linear and nonlinear relationships in the variable space. In addition, we are proposing the alternative use of four terms: (1) linearity as an alternative measure and concept to synchronicity; (2) covariance maps, peaks, etc. as an alternative term to synchronous maps, spectrum, peaks, etc.; (3) disvariance maps, peaks, etc., as an alternative term to asynchronous maps, spectrum, peaks, etc.; and (4) disrelation coefficient as an alternative term to normalized asynchronicity. In an example using FT-IR data from a three-component evaporation experiment, most peaks in the covariance or the traditional synchronous 2D map represented linear relationships, but also peaks representing nonlinear relationships between the involved spectroscopic bands were found. All larger peaks in the disvariance or the traditional asynchronous 2D map represented nonlinear relationships between the involved spectroscopic variables. Our proposed plot visually revealed the type and the degree of non-linearity.
Time-Resolved Laser-Excited Phosphorimetry at Liquid Helium Temperature for the Direct Analysis of 2,3,7,8-Tetrachloro-Dibenzo-Para-Dioxin in Complex Mixtures
Authors: Martin Travis L. , Arruda Andrea F. , Campiglia Andres D.
Published: October 2003

Time-resolved laser-excited phosphorimetry is proposed for the direct analysis of 2,3,7,8-tetrachloro-dibenzo-para-dioxin in complex mixtures at 4.2 K. Measurements are easily made with the aid of a cryogenic fiber-optic probe, which provides excellent precision of measurements and high quality spectra. A tunable dye laser with a narrow bandwidth allows selective excitation in mixtures with highly overlapped excitation spectra. The selectivity of analysis is further enhanced with time-resolution of both fluorescence and phosphorescence interference. Detection at the parts-per-billion level (ng·mL−1) is made with the aid of photon counting. Our results demonstrate the feasibility of detecting 2,3,7,8-tetrachloro-dibenzopara-dioxin in the presence of dioxin isomers and other organic pollutants such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and polychlorinated dibenzofurans. Because of the selectivity of our approach, it was possible to spectroscopically resolve mixtures containing up to 43 components.
Application of FT-IR Spectrometry to Determine the Global Metabolic Adaptations to Physical Conditioning in Sportsmen
Authors: Petibois Cyril , Cazorla Georges , Cassaigne André , Déléris Gérard
Published: October 2003

Global metabolic adaptations to physical conditioning were described in 15 subjects by FT-IR spectrometry as the method allowed determination of glucose (Glc), lactate (La), glycerol, triglycerides (TG), fatty acyl moieties (FAM), and total amino acids plasma concentrations. Subtraction of plasma FT-IR spectra obtained at resting state from the exercise spectra also allowed determination of the biomolecular response to exercise. On week 1, exercise induced a transient hypoglycemia, a lactatemia increase of 153%, a FAM depletion of 27%, and a TG concentration decrease of 28%. Protein contents increased by 2%, but these were partly catabolized for amino acid supply (+27%), suggesting an important metabolic stress during exercise. On week 3, exercise hypoglycemia had disappeared, lactate increase was diminished by 91%, TG contents were decreased by 14%, and proteins and amino acids exhibited higher absorption increases. On week 5, TG and FAM concentrations were markedly increased during exercise, protein absorption was still increased (+9%), but amino acid blood release was diminished by 81%. These results described positive adaptations to training. Furthermore, FAM concentration could be determined from plasma FT-IR spectra by using the 2996–2819 cm−1 spectral area [ νas(CH3), νas(CH2), νs(CH3), and νs(CH2) absorbance; 0.82 mMol·L−1, a.u. cm−1], as well as for amino acid concentration by using the ν(COO−) spectral area (1430–1360 cm−1; 0.062 g·L−1, a.u. × cm−1). FT-IR spectrometry was useful to determine simultaneously various plasma concentrations and most of the biomolecular changes through successive samples.
Improved Data Processing by Application of Brault's Method to Ultra-Rapid-Scan FT-IR Spectrometry
Authors: Yang Husheng , Griffiths Peter R. , Manning Christopher J.
Published: October 2003

In Fourier transform infrared spectrometry, the use of analog-to-digital converters clocked at a constant rate leads to interferograms the data points of which are evenly spaced in time. An interpolation step is generally required to resample these data to equal intervals of retardation. Three methods of resampling the data were compared: Fourier interpolation (i.e., zero-filling), cubic interpolation, and digital filter interpolation as described by Brault. These approaches were investigated using both simulated data and interferograms acquired from an ultra-rapid scanning Fourier transform infrared spectrometer. In both cases, the optical path difference varied sinusoidally with time and interferograms were sampled at equal time intervals. It was shown that the data processing time can be reduced significantly, relative to previous methods, through the application of Brault's method, which can be considered as three separate steps involving a first-, second-, and third-order correction. If only the first-order correction for the local phase relationship between the sampling grids is applied, the noise level of resulting spectra is similar to that obtained by cubic fitting, but the data processing time is reduced significantly. If the second-order correction for the variation of velocity is also used, the data processing time is approximately the same as the first-order correction, while the signal-to-noise ratio of the spectra is increased significantly. The implementation of the third-order correction for channel delay mismatch appears to be unnecessary for this instrument because the detector channel delays are small.
Fluorescence Backgroundless Ti: Sapphire Laser Using Acousto-Optical Tunable Filter for Raman Spectroscopic Measurements
Authors: Sato Hidetoshi , Wada Satoshi , Tashiro Hideo
Published: October 2003

The background noise inherent to tunable lasers, which emit broad band spontaneous fluorescence from the laser-active medium, is detrimental for sensitive Raman measurement. Using the diffraction effect in an acousto-optic device, we have developed a fluorescence backgroundless Ti: sapphire laser suited for near-infrared Raman spectroscopy. A Raman excitation profile consisting of series of Raman spectra of deoxygenated hemoglobin aqueous solutions was measured by changing excitation wavelengths, revealing the high potential of this laser as a spectroscopic light source.
Understanding the Mineralogical Composition of Ancient Greek Pottery through Raman Microprobe Spectroscopy
Authors: Wopenka Brigitte , Popelka Rachel , Pasteris Jill Dill , Rotroff Susan
Published: October 2003

Mineralogical studies using Raman microprobe spectroscopy and high-magnification optical spectroscopy were performed on sherds of pottery vessels that were used as cooking pots and water jars in Hellenistic Greece (third and second century BC). Of specific interest was the mineralogical identification of the so-called inclusions, which are phases that morphologically stand out from the fired clay matrix and result from the presence of inorganic temper in the original paste mixture. The sizes of mono- and polymineralic inclusions in the sherds range from 5 μm to 2 mm. The combined use of Raman microprobe spectroscopy and incident-light optical microscopy permits identification of specific minerals (such as quartz, albite, calcite, hematite, anhydrite, epidote, rutile, anatase, and apatite) in various different types of inclusions and then visual evaluation of the abundance of those minerals in each sample. The application of our nondestructive analytical approach is documented on a set of four sherds (each on the order of several cm2) from excavations of the ancient Agora of Athens. The information on the mineralogy obtained via Raman spectroscopy can shed light on the provenance of the raw materials and firing conditions of the pottery and thus aids archeologists with their historical interpretations.
Spectrometric System for Characterizing Drop and Powder Trajectories and Chemistry in Reactive Flows
Authors: Cabalo Jerry C. , Schmidt John , Wendt Jost O. L. , Scheeline Alexander
Published: October 2003

An instrument for emission, fluorescence, and scattering diagnostics of a 22 kW gas/air thermal reactor is described. Z-pair parabolic mirrors provide diffraction-limited imaging in field center, with worst-case blur over a 12.8 mm field of view having a radius of 0.044 mm rms. Either full-field filtered or transverse line dispersed viewing can occur simultaneously. Dispersion is achieved using a 2-m spectrograph f-matched to the feed optics. Examples of data show non-axisymmetric flow in a nominally laminar flow system, drop shapes in situ, and Mie scattering from soot.
Moisture Quenching of Solid-Matrix Phosphorescence on Hydrophilic and Partially Hydrophobic Filter Papers
Authors: Ackerman Amanda H. , Hurtubise Robert J.
Published: October 2003

A detailed investigation was undertaken to determine the important parameters that were responsible for the solid-matrix phosphorescence (SMP) moisture quenching of phosphors adsorbed in Whatman No. 1 (hydrophilic) and Whatman 1PS (partially hydrophobic) papers. The three phosphors used were phenanthrene, perdeuterated phenanthrene, and benzo[ e]pyrene. Both SMP lifetime and SMP intensity data were obtained over a wide range of adsorbed moisture. In addition, moisture isotherms were obtained for the No. 1 and 1PS papers. The SMP lifetimes of phenanthrene and benzo[ e]pyrene were independent of the amount of adsorbed moisture on both the No. 1 and 1PS papers. However, the SMP lifetimes of perdeuterated phenanthrene on No. 1 and 1PS papers were dependent on the extent of the adsorbed moisture. The changes in the SMP intensities as a function of adsorbed moisture for phenanthrene, benzo[ e]pyrene, and perdeuterated phenanthrene on No. 1 paper could be modeled by a simple exponential function with phenanthrene and benzo[ e]pyrene giving better correlations compared to perdeuterated phenanthrene. The change in the modulus of filter paper samples with moisture adsorption was a major factor in causing the SMP intensity to decrease. The decrease in the SMP intensities with moisture adsorption for the three phosphors adsorbed on 1PS paper did not correlate with the simple Stern–Volmer model and several other quenching models discussed in the literature. Thus, these data were fit to a relatively simple empirical equation. The results showed that the SMP quenching phenomena for the three phosphors on No. 1 paper and on 1PS paper were considerably different.
On-Line Sorting of Wood Treated with Chromated Copper Arsenate Using Laser-Induced Breakdown Spectroscopy
Authors: Moskal T. M. , Hahn D. W.
Published: October 2003

This paper details the design, implementation, and field evaluation of an online detector system using laser-induced breakdown spectroscopy (LIBS) for the analysis of copper chromated arsenate (CCA) treated wood products. The LIBS-based instrument functioned by creating the laser-induced plasma directly on the sample surface while wood was translated under the detector system, and was successful in discriminating between CCA treated wood and untreated wood products based on the atomic emission signal of chromium. The system was optimized for plasma emission collection both in and out of the laser focal plane and temporally optimized for chromium analysis using a compact, non-intensified charge-coupled device (CCD)/spectrometer unit. Using either single laser pulse spectra or 5-shot and 10-shot spectral averages, the accuracy of LIBS-based analysis ranged from 92 to 100% for identifying both CCA treated and untreated wood samples from the waste stream at a construction and demolition debris recycling center. Additional implementation issues are discussed in the context of LIBS-based on-line sorting of construction and demolition wood debris.
Light-Induced Autofluorescence Spectroscopy for Detection of Nasopharyngeal Carcinoma in Vivo
Authors: Chang Hanpeng , Qu Jianan Y. , Yuen Powing , Sham Jonathan , Kwong Dora , Wei William I.
Published: October 2003

Autofluorescence spectral signals were measured in vivo from 85 nasopharyngeal carcinoma lesions and 131 normal tissue sites of 59 subjects during routine nasal endoscopy. Diagnostic algorithms based on principal component analysis and the ratio of the spectral signals between multiple-wavelength bands were developed for classifying the autofluorescence spectra. Performances of the algorithms were evaluated using the cross-validation method. The principal component analysis based algorithms using information from the entire fluorescence spectrum can differentiate nasopharyngeal carcinoma lesions from normal tissue with 95% sensitivity and 93% specificity. With 94% sensitivity, the specificities of multiple-wavelength ratio algorithms are about 83%. The results demonstrate that light-induced autofluorescence endoscopy with principal component analysis algorithms can provide accurate diagnostic information for the detection of nasopharyngeal carcinoma in vivo and may be potentially used in clinical practice combined with the routine white-light endoscopy procedure.
Influence of Temperature on Water and Aqueous Glucose Absorption Spectra in the Near- and Mid-Infrared Regions at Physiologically Relevant Temperatures
Authors: Jensen Peter Snoer , Bak Jimmy , Andersson-Engels Stefan
Published: October 2003

Near- and mid-infrared absorption spectra of pure water and aqueous 1.0 g/dL glucose solutions in the wavenumber range 8000–950 cm−1 were measured in the temperature range 30–42 °C in steps of 2 °C. Measurements were carried out with an FT-IR spectrometer and a variable pathlength transmission cell controlled within 0.02 °C. Pathlengths of 50 μm and 0.4 mm were used in the mid- and near-infrared spectral region, respectively. Difference spectra were used to determine the effect of temperature on the water spectra quantitatively. These spectra were obtained by subtracting the 37 °C water spectrum from the spectra measured at other temperatures. The difference spectra reveal that the effect of temperature is highest in the vicinity of the strong absorption bands, with a number of isosbestic points with no temperature dependence and relatively flat plateaus in between. On the basis of these spectra, prospects for and limitations on data analysis for infrared diagnostic methods are discussed. As an example, the absorptive properties of glucose were studied in the same temperature range in order to determine the effect of temperature on the spectral shape of glucose. The change in water absorption associated with the addition of glucose has also been studied. An estimate of these effects is given and is related to the expected level of infrared signals from glucose in humans.
Using Synchrotron-Based FT-IR Microspectroscopy to Study Erucamide Migration in 50-μm-thick Bilayer Linear Low-Density Polyethylene and Polyolefin Plastomer Films
Authors: Sankhe Shilpa Y. , Hirt Douglas E.
Published: October 2003

The diffusion of additives in thick (∼500 μm) single layer and multilayer films has been characterized using FT-IR microspectroscopy.1,2 The objective of this research was to investigate additive migration and concentration profiles in coextruded multilayer films of industrially relevant thicknesses. In particular, the investigation focused on the migration of an erucamide slip agent in 50-μm-thick coextruded bilayer films of linear low-density polyethylene (LLDPE) and a polyolefin plastomer (POP). Erucamide concentration profiles were successfully mapped using synchrotron-based FT-IR microspectroscopy. The synchrotron radiation helped to achieve a higher spatial resolution for the thin films. Meticulous sample preparation was needed to map the thin film samples. Results with FT-IR microspectroscopy showed that the additive-concentration profiles were relatively uniform across the multilayer-film thickness irrespective of the intended initial additive distribution. For example, a bilayer planned for 1 wt % erucamide in an LLDPE layer and no erucamide in a POP layer showed significant additive migration into the POP layer at the extrusion rates used. FT-IR microspectroscopy results also showed that more erucamide migrated to the surface of a POP layer than an LLDPE layer. Attenuated total reflectance (ATR) FT-IR spectroscopy was used to confirm the time-dependent increase of erucamide surface concentration and that the increase was more pronounced at the surface of the POP layers.
Analysis of Thin Film Coatings on Poly(Ethylene Terephthalate) by Confocal Raman Microscopy and Surface-Enhanced Raman Scattering
Authors: McAnally G. D. , Everall N. J. , Chalmers J. M. , Smith W. E.
Published: October 2003

The characterization of thin coatings on polymers such as poly(ethylene terephthalate) (PET) is required in order to study chemical composition and coating continuity. Two different methods of applying Raman spectroscopy for this purpose are compared in this paper. Using confocal Raman microscopy, thick coatings (>10 μm) are relatively easily identified; however, the Raman scattering from the acrylic coatings commonly used is much weaker than that of PET and consequently, there is a background due to the substrate. Thin acrylic coatings (<1 μm) usually cannot be detected. Surface-enhanced Raman scattering (SERS) of uncoated PET gives intense signals and if the spectra are taken from the metal-coated side, there is no evidence of the underlying Raman scattering from the bulk. Acrylic coatings do not give sufficiently strong or reproducible SERS to be reliably identified, but even thin (20 nm) coatings completely block the SERS from the substrate. Only where gaps appear in the coating is the SERS of the underlying PET seen. To detect a positive signal from the coating, SERS active labels were incorporated into the acrylic at low concentrations either as a physical mixture or as reactive co-monomers. This uniquely labels the coating and allows detection and, in principle, mapping of the coverage. Thus, for thick (≥1 μm) coatings, normal Raman spectroscopy is an effective technique for detecting the presence of the surface coating. However, it is ineffective with thin (<1 μm) coatings, and SERS alone only indicates where the coating is incomplete or defective. However, when a SERS label is added, spectra can be detected from very thin coatings (20 nm). The concentration of the labels is sufficiently low for the coating to remain colorless.
Radiation Dose Distribution in Polymer Gels by Raman Spectroscopy
Authors: Rintoul L. , Lepage M. , Baldock C.
Published: October 2003

The Raman spectroscopy of polymer gel dosimeters has been investigated with a view to developing a novel dosimetry technique that is capable of determining radiation dose within a micrometer of spatial resolution. The polymer gel dosimeter, known as the PAG dosimeter, is typically made up of acrylamide, N,N′-methylene-bis-acrylamide, gelatin, and water. A polyacrylamide network within the gelatin matrix forms in response to an absorbed dose. The loss of monomers may be monitored by corresponding changes to the Raman spectrum. Principal component analysis offers a simple method of quantifying the absorbed radiation dose from the Raman spectrum of the polymer gel. The background luminescence in the spectrum increased significantly with dose and is shown to originate in the glass of the sample vial. The competing effects of elastic scatter, which increases with dose due to the formation of polymer, and sample absorption were quantified and found to introduce errors of up to 5% under certain conditions. Raman spectra as a function of distance from the air–surface interface have been measured for samples that were subjected to doses delivered by a clinical linear accelerator. The depth dose profile thus obtained compared favorably with “gold standard” ion-chamber measurements.
Ultra Violet Resonance Raman Spectroscopy in Lignin Analysis: Determination of Characteristic Vibrations of p-Hydroxyphenyl, Guaiacyl, and Syringyl Lignin Structures
Authors: Saariaho Anna-Maija , Jääskeläinen Anna-Stiina , Nuopponen Mari , Vuorinen Tapani
Published: October 2003

Raman spectroscopy of wood and lignin samples is preferably carried out in the near-infrared region because lignin produces an intense laser-induced fluorescence background at visible excitation wavelengths. However, excitation of aromatic and conjugated lignin structures with deep ultra violet (UV) light gives resonance-enhanced Raman signals while the overlapping fluorescence is eliminated. In this study, ultra violet resonance Raman (UVRR) spectroscopy was used to define characteristic vibration bands of model compounds of p-hydroxyphenyl, guaiacyl, and syringyl lignin structures at three excitation wavelengths (229, 244, and 257 nm). The intensities of each band, relative to the intensity of the aromatic vibration band at 1600 cm−1, were defined and the most suitable excitation wavelength was suggested for each structure. p-Hydroxyphenyl structures showed intensive characteristic bands at 1217–1214 and 1179–1167 cm−1 with excitation at 244 nm, whereas the bands of guaiacyl structures were more intensive with 257 nm excitation. Most intensive characteristic bands of guaiacyl structures were found at 1289–1279, 1187–1185, 1158–1155, and 791–704 cm−1. Syringyl structures had almost identical spectra with 244 and 257 nm excitations with characteristic bands at 1514–1506, 1333–1330, and 981–962 cm−1. The characteristic bands of the three structural units were also found from the compression wood, softwood, and hardwood samples, indicating that UVRR spectroscopy can be applied for the determination of chemical structures of lignin.
Detecting the Signal of the Menstrual Cycle in Fluorescence Spectroscopy of the Cervix
Authors: Cox Dennis D. , Chang Sung K. , Dawood M. Yusoff , Staerkel Gregg , Utzinger Urs , Richards-Kortum Rebecca R. , Follen Michele
Published: October 2003

Fluorescence spectroscopy of the cervix has been shown to be an effective noninvasive diagnostic tool for cervical intraepithelial neoplasia (precancer). To assess the effect of the menstrual cycle on fluorescence spectroscopy, daily measurements were made on ten subjects for the length of their cycle. These measurements were analyzed to determine if there was a statistically significant signal associated with the menstrual cycle. A signal was found for emission wavelengths between 425 and 445 nm inclusive—near the main hemoglobin absorption band, the Soret band, at 420 nm. We suspect that the slight displacement of the Soret band is due to the nearby dominant NAD(P)H peak, which increases the signal-to-noise ratio and affects statistical significance. The signal consists of a reduction in fluorescence intensity for the first few days of the cycle. This analysis indicates that hemoglobin absorption is the main menstrual-cycle effect on the use of fluorescence spectroscopy on the cervix. The effect is confined to a small set of excitation/emission wavelengths and to approximately the first 8 days of the cycle. This suggests that any problems from the menstrual cycle can be avoided with a simple requirement that the device not be used during the period of menstrual bleeding.
Evaluation of Acridine in Nafion as a Fluorescence-Lifetime-Based pH Sensor
Authors: Ryder Alan G. , Power Sarah , Glynn Thomas J.
Published: October 2003

We report a novel fluorescence-lifetime-based pH sensing method that utilizes acridine incorporated into Nafion (AcNaf) as the fluorescent indicator. The AcNaf sensor is excited using a 380 nm light emitting diode (LED) and the fluorescence lifetimes are measured at 450 and 500 nm. The fluorescence behavior of acridine as a function of pH in aqueous phosphate buffers and incorporated into the Nafion membrane has been investigated. The results show that incorporating acridine into Nafion changes the apparent ground-state pKa from ∼5.45 to ∼9, while the apparent excited-state pKa* is only slightly changed (∼9.4 in 0.1 M phosphate buffer). The AcNaf film shows a good pH response with a change in average lifetime of ∼19 ns (at an emission wavelength of 450 nm) over the pH 8 to 10 range. We also show that excited-state protonation does not occur in the AcNaf sensor film and that chloride quenching cannot occur because of the permselective nature of Nafion. We also discuss how the unique structure of Nafion affects the fluorescence behavior of acridine at various pH values and examine the impact of buffer concentration on apparent pKa and pH sensing ability.
Design and Application of a New Cell for in Situ Infrared Reflection–Absorption Spectroscopy Investigations of Metal–Atmosphere Interfaces
Authors: Kleber CH , Kattner J. , Frank J. , Hoffmann H. , Kraft M. , Schreiner M.
Published: October 2003

A new experimental setup for studying reactions occurring in the metal–atmosphere interface by applying in situ infrared reflection–absorption spectroscopy (IRRAS) is presented. It consists of a gas-mixing unit, where the moist air is generated with or without corrosive gases, the reaction cell for the in situ investigations, and an optical system coupled with a Fourier transform infrared (FT-IR) spectrometer. For testing the unit, a specimen of pure copper was used, where the growth of Cu2O on the polished surface could be observed during time-resolved measurements in synthetic air containing 80% RH (relative humidity). For comparison of the experimental results obtained, a computer simulation program was developed in order to calculate the peak position, the peak height, the peak width, and the thickness of the surface layer formed during the atmospheric corrosion. The simulation software is based on the four-phase model of covered surfaces.
Crossed Two-Beam Coherent Anti-Stokes Raman Spectroscopy in Dispersive Media
Authors: Papac Michael J. , Posner Jonathan D. , Dunn-Rankin Derek
Published: October 2003

Coherent anti-Stokes Raman spectroscopy (CARS) is a nonlinear optical wave mixing process that is used in gas-phase systems to determine the energy distribution of the probed species (usually N2) and, through a fitting procedure, the temperature giving rise to it. CARS signal strengths are maximized when the phase matching condition is met. Because gases are generally non-dispersive, this phase matching condition can be found geometrically as a function of the crossing angles between the CARS beams and their wavelengths. In addition, perfect phase matching in non-dispersive media occurs automatically for collinear beams. To improve spatial resolution, however, intersecting the laser beams is desirable. Being a third-order process, phase matching for CARS in gases typically requires three input laser beams. This paper discusses and demonstrates the issues of phase matching for CARS when the medium is dispersive, and the ability for CARS phase matching to occur with only two crossed laser beams (one pump and one probe). This two-beam X-CARS in dispersive media can be used as an alignment tool for gas-phase CARS and may be relevant as a simpler diagnostic in high-pressure environments. The paper also discusses the effects of non-ideal phase matching in dispersive and non-dispersive media.
Application of Multivariate Curve Resolution for Analysis of FT-IR Microspectroscopic Images of in Situ Plant Tissue
Authors: Budevska Boiana O. , Sum Stephen T. , Jones Todd J.
Published: October 2003

The chemometric techniques of multivariate curve resolution (MCR) are aimed at extracting the spectra and concentrations of individual components present in mixtures using a minimum set of initial assumptions. We present results from the application of alternating least squares (ALS) based MCR to the analysis of hyperspectral images of in situ biological material. The spectra of individual pure components were mathematically extracted and then identified by searching the spectra against a commercial library. No prior information about the chemical composition of the material was used in the data analysis. The spectra recovered by ALS-MCR analysis of an FT-IR microspectroscopic image of an 8-μm-cornkernel section matched very well the spectra of the corn storage protein, zein, and starch. Through the application of MCR, we were able to show the presence of a second spectrally different protein, which could not be easily seen using univariate analysis. These results demonstrate the value of multivariate curve resolution techniques for the analysis of biological tissue. The value of principal components analysis (PCA) for hyperspectral image analysis is also discussed.
Short-Wavelength Near-Infrared Spectra of Sucrose, Glucose, and Fructose with Respect to Sugar Concentration and Temperature
Authors: Golic Mirta , Walsh Kerry , Lawson Peter
Published: October 2003

Short-wavelength near-infrared (SW-NIR) (700–1100 nm) spectra of aqueous solutions of sucrose, d-glucose, and d-fructose were monitored with respect to change in temperature and sugar concentration. Sugar OH and CH related vibrations were identified by analysis of the spectra of sugar solutions in deuterium oxide (D2O), and of sucrose- d8 solutions in D2O. Absorption spectra were explained in terms of the second and third overtones of OH stretching vibrations and the third overtone of CH2 and CH stretchings. In deuterated solutions, CH and CH2 higher overtone vibration bands became apparent. The major spectral effect of decreased temperature or increased sugar concentration was a decrease in absorbance at 960 nm and an increase in absorbance at 984 nm, interpreted as an increase in the degree of H bonding. Partial least-squares (PLS) calibrations on sugar concentrations (with spectra collected at several sample temperatures) relied strongly on the 910 nm sugar CH related bands, whereas calibrations on temperature depended equally on all OH associated vibrations (750, 840, 960, and 985 nm).
Investigation of Electrolyte Measurement in Diluted Whole Blood Using Spectroscopic and Chemometric Methods
Authors: Soller Babs R. , Favreau Janice , Idwasi Patrick O.
Published: October 2003

The feasibility of using near-infrared (NIR) spectroscopy in combination with partial least-squares (PLS) regression was explored to measure electrolyte concentration in whole blood samples. Spectra were collected from diluted blood samples containing randomized, clinically relevant concentrations of Na+, K+, and Ca2+. Sodium was also studied in lysed blood. Reference measurements were made from the same samples using a standard clinical chemistry instrument. Partial least squares (PLS) was used to develop calibration models for each ion with acceptable results (Na+, R2 = 0.86, CVSEP = 9.5 mmol/L; K+, R2 = 0.54, CVSEP = 1.4 mmol/L; Ca2+, R2 = 0.56, CVSEP = 0.18 mmol/L). Slightly improved results were obtained using a narrower wavelength region (470–925 nm) where hemoglobin, but not water, absorbed indicating that ionic interaction with hemoglobin is as effective as water in causing measurable spectral variation. Good models were also achieved for sodium in lysed blood, illustrating that cell swelling, which is correlated with sodium concentration, is not required for calibration model development.
Absorption of Water by Room-Temperature Ionic Liquids: Effect of Anions on Concentration and State of Water
Authors: Tran Chieu D. , De Paoli Lacerda Silvia H. , Oliveira Daniel
Published: October 2003

Near-infrared (NIR) spectrometry was successfully used for the noninvasive and in situ determination of concentrations and structure of water absorbed by room-temperature ionic liquids (RTILs). It was found that RTILs based on 1-butyl-3-methylimidazolium, namely, [BuMIm]+[BF4]−, [BuMIm]+[bis((trifluoromethyl)sulfonyl)amide, or Tf2N]− and [BuMIm]+[PF6]−, are hydroscopic and can quickly absorb water when they are exposed to air. Absorbed water interacts with the anions of the RTILs, and these interactions lead to changes in the structure of water. Among the RTILs studied, [BF4]− provides the strongest interactions and [PF6]− the weakest. In 24 hours, [BuMIm]+[BF4]− can absorb up to 0.320 M of water, whereas [BuMIm]+[PF6]− can only absorb 8.3 × 10−2 M of water. It seems that higher amounts of water can be absorbed when the anion of the RTIL can strongly interact and hence stabilize absorbed water molecules by forming hydrogen bonds with them or inducing hydrogen bonds among water molecules. More importantly, the NIR technique can be sensitively used for the noninvasive, in situ determination of absorbed water in RTILs, without any pretreatment, and at limits of detection as low as 3.20 × 10−3 M.