bluuebunny/crossref_metadata_2025 huggingface dataset:
Standardization of Fiber-Optic Probes for Near-Infrared Multivariate Calibrations
Authors: Sum Stephen T. , Brown Steven D.
Published: October 2003

The standardization of Fourier transform near-infrared (FT-NIR) spectrometers equipped with fiber-optic probes was investigated. FT-NIR spectra of caustic brines for an industrial process were measured on two different instruments. Calibration transfer across the instruments and probes was studied by employing calibration models built on one instrument to predict properties from spectra measured on the other. The transfer was examined by using spectra without and with preprocessing. The preprocessing methods included a Savitzky–Golay (SG) derivative polynomial filter, a procedure based on a finite impulse response (FIR) filter, and a combination of both. In addition to being a preprocessing technique, the FIR filter is also a standardization method that transforms the instrument response function of one instrument to match that of another. The transformation is performed over a moving processing window without the use of transfer standards. In this study, application of the FIR filter to first-derivative spectra provided the best multivariate calibration models and led to the successful transfer of calibration across different probes and spectrometers.
Assessment of Partial Least-Squares Calibration and Wavelength Selection for Complex Near-Infrared Spectra
Authors: McShane Michael J. , Coté Gerard L. , Spiegelman Clifford H.
Published: October 2003

Complex near-infrared (near-IR) spectra of aqueous solutions containing five independently varying absorbing species were collected to assess the ability of partial least-squares (PLS) regression and wavelength selection for calibration and prediction of these species in the presence of each other. It was confirmed that PLS calibration models can successfully predict chemical concentrations of all five chemicals from a single spectrum. It was observed from the PLS spectral loadings that spectral regions containing absorption bands of a single analyte alone were not sufficient for the model to adequately predict the concentration of the analyte because of the high degree of overlap between glucose, lactate, ammonia, glutamate, and glutamine. Three wavelength selection algorithms were applied to the spectra to identify regions containing necessary information, and in each case it was found that nearly the entire spectral range was needed for each determination. The results suggest that wavelength selection does result in a reduction of data points from the full spectrum, but the decrease seen with these near-infrared spectra was less than typically seen in mid-IR or Raman spectra, where peaks are narrower and well separated. As a result of this need for more wavelengths, the engineering of a dedicated system to measure these analytes in complex media such as blood or tissue culture broths by using this near-infrared region (2.0–2.5 μm) is further complicated.
Simultaneous Detection of C6H5NHD, C6H5ND2, C6D5NH2, C6D5NHD, and C6D5ND2 by Resonant Two-Photon Ionization Mass Spectrometry
Authors: Tzeng W. B. , Narayanan K. , Chang G. C.
Published: October 2003

The resonant two-photon ionization (R2PI) spectra of jet-cooled C6H5NH2, C6H5NHD, C6H5ND2, C6D5NH2, C6D5NHD, and C6D5ND2 resulting from the S1← S0 electronic transition have been simultaneously recorded in three different sample mixtures. New data on C6H5NHD and C6D5NHD are presented for the first time. The observed R2PI spectral bands of these species are successfully assigned on the basis of observed frequency shifts in some vibrational modes of deuterated species and calculated ab initio values. On the basis of mass separation and optical spectral analyses, this method provides an unambiguous means for the simultaneous and selective detection of isotopically substituted anilines presented in the mixture.
Microwave-Assisted Vapor-Phase Nitric Acid Digestion of Small Biological Samples for Inductively Coupled Plasma Spectrometry
Authors: Amarasiriwardena Dula , Krushevska Antoaneta , Barnes Ramon M.
Published: October 2003

The applicability of microwave-assisted, vapor-phase nitric acid digestion of small biological samples in closed-vessel microwave systems is examined for the inductively coupled plasma atomic emission spectroscopy (ICP-AES) determination of 10 elements (Al, As, Ca, Cu, Cd, Fe, Mn, Mo, Pb, and Zn). A 1.8 mL quartz sample container geometry was optimized for the successful decomposition of 50 to 90 mg of powdered biological samples. Microwave energy was efficiently coupled by addition of 250 μL of distilled deionized water to the sample. A single microwave-assisted, vapor-phase acid sample digestion was accomplished within 30 min (including cooling time) at ∼1200 psi pressure and 450 W microwave power in a commercial pressurized microwave decomposition (PMD) system. Multiple microwave-assisted, vapor-phase acid digestions were achieved at moderately high pressure (400 to 480 psi) and 230 °C with a second closed-vessel microwave apparatus. The results for 10 elements in biological standard reference materials agree well with the certified values.
Raman Imaging of Emulsion Systems
Authors: Andrew Jeremy J. , Browne Mark A. , Clark Ian E. , Hancewicz Tom M. , Millichope Allen J.
Published: October 2003

The use of Raman microscopy in imaging two emulsion systems is described. Registered optical microscopy and Raman images are collected, the latter describing the chemical basis of the heterogeneity observed in the former. These examples act as a powerful demonstration of the application of the Raman microscopy technique to the analysis and understanding of microstructure in commercial products. The results indicate how the principles of Raman imaging can be applied to complex, multicomponent, multiphase systems of inherently low contrast. Such systems are of importance because they represent a wide variety of commercial product systems, ranging from pharmaceutical creams through skin creams and toothpastes. The use of a software environment for the organization, storage, management, interrogation, and manipulation of multidimensional spectral imaging data is also described. The important factors to be considered in determining the full information content of such data sets are established, and suggestions as to how such data sets can be optimally interrogated are made.
Rapid Analysis of Raman Image Data Using Two-Way Multivariate Curve Resolution
Authors: Andrew Jeremy J. , Hancewicz Thomas M.
Published: October 2003

The application of standard two-way curve resolution methods is reported for analysis of three-way Raman image data. Two current curve resolution methods are described: principal factor multivariate curve resolution (PF-MCR), which uses principal factor analysis (PFA) combined with varimax rotation and alternating least-squares optimization (ALS), and orthogonal projection multivariate curve resolution (OP-MCR), which uses a Gram–Schmidt modified orthogonal projection approach (OPA) followed by ALS. The OP-MCR technique is shown to be an extremely rapid method of analysis producing results equivalent to those of PF-MCR in one-third to one-fourth the time. The results from MCR analysis using either method provide the number of chemical species present in the sample, the spectrum of each species for identification, and the concentration image for each species. The additional benefit of image noise reduction also results from the MCR techniques. A brief description of the theory is presented followed by analysis and comparison of results for two real Raman image data. A discussion is given addressing the rapid analysis aspects of OP-MCR and the relative merits and drawbacks of the technique in comparison to PF-MCR. The use of data subsampling is also discussed as a way of decreasing analysis time without loss in accuracy or performance.
Study of the Hydrolysis of Sodium Polyphosphate in Water Using Raman Spectroscopy
Authors: De Jager Henk-Jan , Heyns Anton M.
Published: October 2003

Raman spectroscopy is used to monitor hydrolysis of a polyphosphate dissolved in water at pH = 0. It is found that this reaction is of zeroth-order and obeys the Arrhenius equation with Ea = 57 kJ·mole−1. Hydrolysis predominantly takes place at terminal phosphate units, and, although random hydrolysis might be involved in the process, its contribution is shown to be very small with respect to the overall process.
Raman Study of Enzyme Reactions Using Potassium Ferricyanide as a Reaction Mediator: Quantitative Analysis of Substrates and Measurement of Enzyme Activity for Glucose Oxidase and Lactate Oxidase
Authors: Dou Xiaoming , Ozaki Yukihiro
Published: October 2003

This paper describes a Raman study of enzyme reactions that use potassium ferricyanide as a reaction mediator. The enzyme reaction systems investigated consisted of glucose oxidase (GOD), glucose, and potassium ferricyanide, and of lactate oxidase (LOD), lactate, and potassium ferricyanide. Raman spectra were measured for the above enzyme systems every 2 s to monitor the progress of the enzyme reactions at real time. The observed Raman spectra showed only three peaks at 2186, 2095, and 2022 cm−1 due to C N stretching modes of potassium ferricyanide (2186 cm−1) and potassium ferrocyanide (2095 and 2022 cm−1); with the progress of the enzyme reactions, the band at 2186 cm−1 decreases while those at 2095 and 2022 cm−1 increase. From the differentiation of the Raman intensity at 2022 cm−1, we could calculate the velocity ( V′) of the intensity change that directly reflects the rate ( V) of the enzyme reactions. By plotting the velocity thus obtained ( V′) vs. the concentration of the enzyme substrate ([ S]), we were able to develop a calibration curve to predict the concentration of the enzyme substrate. For GOD, the correlation coefficient ( R) and the detection limit of this calibration curve were 0.99 and 20 mg/dL, respectively. This detection limit was better than that obtained from conventional glucose sensors. For LOD, we were able to determine Michaelis constant ( Km) from the maximum velocity ( Vmax). The method proposed here is applicable to various kinds of enzymes that use potassium ferricyanide as a reaction mediator.
Identification of Colonic Dysplasia and Neoplasia by Diffuse Reflectance Spectroscopy and Pattern Recognition Techniques
Authors: Ge Zhengfang , Schomacker Kevin T. , Nishioka Norman S.
Published: October 2003

Diffuse reflectance spectroscopy of colonic tissue was employed to determine whether the spectra can be used to distinguish between neoplastic and non-neoplastic tissue in vivo. A total of 224 spectra were obtained in the wavelength range of 350–800 nm from 107 non-neoplastic tissue samples (84 normal mucosa, 23 hyperplastic polyps) and 53 neoplastic tissue samples (44 adenomatous polyps, 9 adenocarcinomas). Pattern recognition algorithms including multiple linear regression (MLR), linear discriminant analysis (LDA), and backpropagating neural network (BNN) were used to distinguish between the two tissue classes. The spectra were randomly separated into training and prediction sets for data analyses. The mean predictive accuracies of distinguishing neoplastic tissue from non-neoplastic tissue with MLR, LDA, and BNN were 85, 82, and 85%, respectively. In a similar fashion, the more clinically relevant problem of distinguishing adenomatous polyps from hyperplastic polyps was assessed. The mean predictive accuracies of distinguishing adenomatous polyps from hyperplastic polyps with MLR, LDA, and BNN were 85, 81, and 82%, respectively. The major spectral differences between tissues were attributed to changes in blood volume, oxygen saturation of hemoglobin, mean vessel depth within tissue, and tissue scattering.
Fractional Derivative Analysis of Diffuse Reflectance Spectra
Authors: Schmitt Joseph M.
Published: October 2003

Fractional differentiation is introduced as a mathematical tool for analysis of diffuse-reflectance spectra. The quantity —log10 e/R dqR/ dλ q, where R is the measured reflectance and q is a real number greater than zero, is defined and shown to have properties analogous to those of the integer-order derivatives of log10(1/ R) that are commonly employed in near-infrared spectroscopy. Like conventional derivative spectroscopy, fractional derivative spectroscopy (FDS) is effective for reducing baseline variations and separating overlapping peaks. FDS has the additional benefit that it enables the user to control the weight given to the slope and curvature of spectral features and, therefore, provides greater flexibility in the choice of wavelengths for regression. FDS also enables the user to adjust the relative sensitivities of the regressions to constant offsets and high-frequency noise. An example is given in which FDS is used to estimate the concentration of hemoglobin in a scattering liquid containing a large background concentration of water.
Baseline Correction of Spectra in Fourier Transform Infrared: Interactive Drawing with Bézier Curves
Authors: Koch Alain , Weber Jean-Victor
Published: October 2003

A baseline correction tool using the method of Bézier has been developed to permit the drawing of curves in a manner that allows full control of the line curvatures by the user. The basic concepts and principle of the Bézier algorithm are explained as well as the modifications that were made to take into account the limitations imposed by the treatment of spectral data. The application of this particular curve drawing routine to an existing baseline correction module offers facilities and extended capabilities that typical polynomial methods using least-squares fitted lines cannot attain. The examples of applications that are given demonstrate how this method can be performed, as well as its efficiency.
Direct Phase Correction of Differential FT-IR Spectra
Authors: Hutson M. Shane , Braiman Mark S.
Published: October 2003

Step-scan transient Fourier transform infrared (FT-IR) difference spectra are often measured in an ac-coupled configuration. The resulting differential intensity spectra contain both positive and negative bands. This condition poses problems for direct phase correction by the standard Mertz and Forman methods. Restricting the calculated phase angle to the range [–π/2, π/2] was previously shown to fix some of these problems, but we show that the use of a reduced-resolution phase spectrum can produce other artifacts. The effect of reduced resolution is analyzed for a simulated noise-free spectrum and for a measured transient spectrum of a real photochemical system, bacteriorhodopsin. Examination of these results reveals that the Mertz and Mertz Signed methods can produce spectral bands of reduced magnitude and unusual band shape, with considerable amounts of intensity remaining along the imaginary axis after phase correction. However, these errors can be eliminated by self-convolution of the measured interferogram, which doubles all phase angles, prior to smoothing. This procedure removes the potential discontinuities in the phase angle due to sign changes in the differential spectrum. With bacteriorhodopsin, this doubled-angle method for direct phase correction is able to produce a transient spectrum which closely matches that produced by using a separately measured dc interferogram to calculate the phase angle.
FT-IR Study of the Imidization Process of Photosensitive Polyimide PMDA/ODA
Authors: Li W. S. , Shen Z. X. , Zheng J. Z. , Tang S. H.
Published: October 2003

Fourier transform infrared spectroscopy (FT-IR) was used to study the cure reaction process of an ester-type photosensitive polyimide, PMDA/ODA films coated on silicon wafer substrates. In the in situ high-temperature FT-IR study carried out in vacuum, all the characteristic peaks of imide and the crosslinkable group were observed to decrease gradually with an increase in temperature. The completion of the imidization reaction is at ∼270 °C. Our result shows that the ester-type photosensitive polyimide can be cured at a much lower temperature than previously reported. The imide peak δas(C, C > NC) at 588 cm−1 was used to follow the imidization process, and the result agrees well with that obtained by using another imide peak v(C–N–C) at 1378 cm−1. The film shrinks by one third during the cure process, and the temperature dependence of the film thickness shows excellent agreement with the “imidization degree”.
Application of Fourier Transform Infrared Spectroscopy in Quantitation of Trierucin in High-Erucic-Acid Rapeseed Oils
Authors: Ahmed M. Khalique , Daun Jim , Declercq Doug
Published: October 2003

Development of varieties of high-erucic-acid (HEAR) rapeseed with high levels of erucic acid (C22:1) would be valuable for use in oleochemical feedstocks. As an aid to this breeding effort, a rapid method to detect trierucin (C22:1 triacylglycerol), an indicator that erucic acid is being incorporated in all three positions of the triacylglycerol, would be useful. Fingerprint (1850–600 cm−1) Fourier transform infrared (FT-IR) spectra of HEAR oil extracted from Brassica napus L. cv. Mercury, trierucin, and varying amounts of trierucin spiked in this oil were recorded. The regions of 1790–1690 cm−1 and 1485–990 cm−1 were subjected to a partial least-squares (PLS) procedure to obtain a calibration equation [ R2 = 0.992 and root-mean-squared deviation (RMSD) = 2.78]. The established calibration was then tested on the spectra of mixtures of another HEAR oil from B. napus cv. Turret and trierucin. The predicted values differ from the actual values with an RMSD of 1.6%. The calibration was also tested on high-erucic-acid oils from crambe ( Crambe abyssinica) and nasturtium ( Tropaeolum majus L.) seeds. For crambe, the value found (0.4%) was close to that reported in the literature, while the value of 75% for nasturtium oil was close to the value for total triacylglycerols with erucic acid in the 2-position as reported in the literature. FT-IR spectra of triolein (C18: 1 triacylglycerol), trieicosenoin (C20:1 triacylglycerol), and trinervonin (C24:1 triacylglycerol) compared with the FT-IR spectrum of trierucin revealed the uniqueness of IR spectrum of trierucin that forms the basis of PLS analysis of trierucin in HEAR oils.
Resolution Enhancement and Band Assignments for the First Overtone of OH Stretching Mode of Butanols by Two-Dimensional Near-Infrared Correlation Spectroscopy. Part I: sec-Butanol
Authors: Czarnecki Mirosław A. , Maeda Hisashi , Ozaki Yukihiro , Suzuki Masao , Iwahashi Makio
Published: October 2003

The first paper in a series devoted to self-association in neat butanols presents the results of two-dimensional (2D) near-infrared (NIR) correlation analysis of temperature-induced spectral variations of sec-butanol. By taking advantage of resolution enhancement in the 2D correlation spectra, it was possible to identify spectral features due to vibrations of the free and associated OH groups in the first-overtone region. On the basis of a few assumptions, band assignments of the various types of OH bonds have been proposed. The monomer band (near 7100 cm−1) can be resolved into three components; two of them are due to a rotational isomerism (7089 and 7116 cm−1), and the third one is attributed to the free terminal OH groups in linear polymers (7055 cm−1). The presence of the 7055 cm−1 band implies that the intensity of the monomer peak cannot be used as a measure of the concentration of the monomer species (except in very diluted solutions). Thus, previous estimations of equilibrium constants and thermodynamic parameters associated with hydrogen-bond dissociation have been subject to unacceptable error. At higher temperatures, a new band near 6550 cm−1 becomes visible. This band originates from bended OHO bond, mostly in the cyclic polymers. In order to obtain more detailed information on the complex mechanism of the thermal dissociation of hydrogen-bonded sec-butanol in the pure liquid phase, the entire experimental temperature range was divided into narrower ranges, and then 2D correlation analysis was performed for smaller data sets. It has been shown that the variations of population of the polymeric species and the cyclic dimers are faster than the corresponding changes for the monomers. At elevated temperatures an appreciable dissociation of the cyclic species takes place.
In vivo Measurements of Water in Skin by Near-Infrared Reflectance
Authors: Martin Kathleen
Published: October 2003

Near-infrared (NIR) reflectance spectroscopy has been used to differentiate water in different hydrogen-bonding environments of skin in vivo and to determine the effect of moisturizer application on water content. Four types of water have been observed in the second-derivative spectrum of skin. These are assigned as water associated with the lipid bilayers, primary and secondary water of hydration on protein, and bulk (free) water in deeper tissue. The intensities of the lipid-associated water band and the bulk water band depend on anatomical site. The latter, particularly, may be affected by corneocyte size and may have potential in predicting transdermal penetration of drugs. Moisturizer application appears to have little effect on water content, but results in changes in the degree of scattering of radiation, suggesting that moisturizers smooth, rather than hydrate, the skin.
Proposal for High-Resolution, Wide-Bandwidth, High-Optical-Throughput Spectroscopic System Using a Fabry—Perot Interferometer
Authors: Iwata Tetsuo , Koshoubu Jun
Published: October 2003

We propose a high-resolution, wide-bandwidth, high-optical-throughput spectroscopic system, in which a Fabry–Perot interferometer (FPI) is used in tandem with a second spectrometer. As the second spectrometer, one of the following three instruments can be used: (1) a grating dispersion-type monochromator attached to a multichannel detector (MCD), (2) a conventional Fourier transform spectrometer (FTS), or (3) a multichannel FTS (MFTS). The principle of operation for the three systems is the same. First, we adjust the free spectral range ( FSR) of the FPI to be k (>1) times the data interval DI (or resolved wavenumber) of the second spectrometer. The FSR is divided by N (> k) equally, and the etalon plate spacing of the FPI is changed N times with a step interval of FSR/N in wavenumber. Thereby we gather a total of N spectra from the second spectrometer. Finally, a single high-resolution spectrum is synthesized from the N spectra. To demonstrate the real capabilities of the proposed systems, we present computer simulation results.
Photodeposition of Diffraction Gratings in Glass
Authors: Sunil D. , McQuade Arthur W. , Gafney Harry D.
Published: October 2003

Line patterns with spacings ranging from 10 to 50 μm have been achieved by 488 nm photolysis of porous glasses impregnated with Fe(CO)5. Photolysis was accomplished with a focused Ar+ laser impinging onto a sample mounted on a computer-controlled X-Y stage programmed to create a line pattern. The photodeposited grating was tested by generating a diffraction pattern with a He–Ne laser, which was then used to calculate the grating line spacings. The measured line spacings were found to be in excellent agreement with the spacings defined by the computer-driven stage. Consolidation of the porous glass occurs at 1200 °C, and decreases the sample volume as much as 35%. Line spacing decreases in direct proportion to the decrease in the dimension perpendicular to the grating lines of the sample and consolidation yields gratings that are capable of diffracting light, stable under a variety of conditions, and unaffected by high laser powers.
Adsorption Gas Flow Modulator for Sensitivity Increase of Mass-Spectrometric Measurements
Authors: Kvitsinsky V. A. , Krivosheev S. I. , Makarchuk V. N.
Published: October 2003

A possibility for modulation of molecular flow through a capillary by its periodic heating and cooling has been investigated. The Knudsen gas flow (when the length of the molecule free path is greater than the diameter of the capillary) at variable temperatures of the capillary and the linear isotherm of adsorption have been analyzed in terms of diffusion approximation. The analytical expression for the outlet flow has been obtained for any given time dependence of the capillary temperature and inlet flow. It has been demonstrated that such modulation can increase both sensitivity and selectivity of mass spectrometric measurements and could be used for on-line analysis of gas streams.
Two-Photon Excitation Profiles in Cylindrical Capillaries
Authors: Overway K. S. , Lytle F. E.
Published: October 2003

Poor detection limits of two-photon excited fluorescence in cylindrical capillaries are attributed to photothermal expansion and beam astigmatism. Photothermal expansion is demonstrated for excitation in a 1 cm cell and is inferred for the larger diameter capillaries. Astigmatism is caused by focal differences between rays in a plane longitudinal to the capillary and rays in a plane transverse to the capillary. Data were obtained by integrating the fluorescence from variously sized cylindrical and square capillaries, and by photographing the fluorescence within a 1 cm cell.
Method to Determine Tissue Fluorescence Efficiency in vivo and Predict Signal-to-Noise Ratio for Spectrometers
Authors: Trujillo E. V. , Sandison D. R. , Utzinger U. , Ramanujam N. , Mitchell M. Follen , Richards-Kortum R.
Published: October 2003

Recent clinical trials have demonstrated the potential of fluorescence spectroscopy for in vivo diagnosis of pathology. There is significant potential to reduce the cost and complexity of instrumentation to measure tissue spectra; however, careful analysis is required to maximize performance and minimize cost. One measure of performance is the signal-to-noise ratio (SNR) of the resulting data. This paper describes a method to predict the SNR of a given optical design for a particular tissue application. In order to calculate the expected SNR, two pieces of information are required: (1) the throughput and inherent noise of the system and (2) a quantitative relationship between the illumination energy and the resulting tissue fluorescence available for collection, which we define as the tissue fluorescence efficiency (FE). We present a method to calculate the fluorescence efficiency of tissue from in vivo measurements of tissue fluorescence. We report FE measurements of the normal and precancerous human cervix in vivo at 337, 380, and 460 nm excitation. We also present and evaluate a method to estimate the throughput and noise of various spectrometers and predict the expected SNR for tissue spectra by using the measured tissue FE. For squamous cervical tissue, as the degree of the disease increases, FE decreases, and as the excitation wavelength increases, FE decreases. Cervical tissue FE varies more than two orders of magnitude, depending on the tissue type and on the excitation wavelength used. Our SNR calculations, based on measured values of tissue FE, demonstrate agreement within a factor of 1.3 of the measured SNR on average. This method can be used to estimate the performance of different spectrometer designs for clinical use.
Spectroscopic Studies of Brilliant Cresyl Blue/Water-Soluble Sulfonated Calix[4]Arene Complex
Authors: Zhang Yuling , Pham Tuyet H. , Peña Montserrat Sánchez , Agbaria Rezik A. , Warner Isiah M.
Published: October 2003

Water-soluble sulfonated calix[4]arene (SCX4) was used as the host molecule for the guest dye(probe), Brilliant Cresyl Blue (BCB), which is commonly employed for studies of various biological systems. Absorption and fluorescence techniques were employed for the analysis of this system. The formation of a complex between the BCB dye and SCX4 results in a decrease in the BCB fluorescence intensity. A study of the changes in absorption and of temperature effects on the fluorescence of BCB/SCX4 was conducted. The binding constant for BCB/SCX4 at room temperature was estimated to be 8.49 × 103 M−1.
Advanced in situ Sapphire Test Cell for Raman Spectroscopy within Aqueous Environments
Authors: Carey David M. , Plesko Eric P. , Outwater John O.
Published: October 2003

A simple and inexpensive sapphire test cell has been developed for the performance of in situ Raman spectroscopy within aqueous environments up to the conditions of 400 °C and 345 bar pressure. The cell volume is approximately 11 cm3 and is held by a heating enclosure within the optical path of a Raman spectrometer. With this cell, Raman vibrational measurements have been satisfactorily performed on aqueous samples and on solid substrates within aqueous environments. The test cell and its supporting equipment are fully described, as well as the Raman data manipulation method used for the processing of high-temperature aqueous Raman measurements.
Synchrotron Infrared Microspectrometry Applied to Petrography in Micrometer-Scale Range: Fluid Chemical Analysis and Mapping
Authors: Guilhaumou N. , Dumas P. , Carr G. L. , Williams G. P.
Published: October 2003

The potentiality of synchrotron infrared microspectrometry was investigated for in situ analysis of fluid inclusions and volatiles of particular geological interest. Thanks to the intrinsic high brightness of the synchrotron infrared source, areas as small as a few μm2 can be probed, providing a high-contrast analysis of small inclusions in geological materials. We have identified organic components in such small volumes in their liquid and gaseous phase, thus allowing a deeper analysis of oil-water inclusions entrapped in diagenetic cements. Such detailed analysis opens up new perspectives in petroleum reservoir evolution studies. The high signal-to-noise ratio of spectra obtained in small volume allows a fast and accurate chemical mapping of the inclusion components. Drastic refraction effects preclude, at the present state, a quantitative analysis of either the volume or the thickness of the individual inclusions. Traces of volatiles such as CO2 and H2O are easily detected in the vitreous and gaseous part of the glass melt fluid inclusions. We have also profiled the hydroxyl concentration near a wall, and calculated the hydrogen diffusion coefficient in anhydrous minerals such as diopside.
Distributed Fiber-Optic Chemical Sensor with Chemically Modified Plastic Cladding
Authors: Potyrailo Radislav A. , Hieftje Gary M.
Published: October 2003

A novel method for modification of the polymer cladding of an optical fiber has been developed for use in distributed chemical sensing. The usefulness of the new technique is illustrated by means of a distributed sensor for ammonium ions based on a 9 m long plastic-clad silica fiber modified with phenol red. The stability of the immobilized indicator made it possible, for the first time, to use a chemically modified fiber for the reversible detection of ammonium ions in highly alkaline solution (pH 11–14). The new sensor offers a broader dynamic range (four orders of magnitude) and shorter response time (30 s) than point sensors for ammonium ions reported in the past.
Novel Experimental Technique for the Absolute Determination of Quantum Yields
Authors: Kaindl G. , Weger R. , Bajons P.
Published: October 2003

A new method for the absolute determination of the quantum yield based on the trapping of fluorescence light within a cylinder is discussed. First the trapping probability of photons—which are emitted in transparent rods or fluid-filled tubes—is investigated theoretically. The studies are based on the extension of light governed by the laws of reflection and refraction. The effect of nonhomogeneous distribution of the centers of fluorescence light emission on the calculation procedures is taken into account. Then the adaptation of the theoretical results to a new practical method is shown. The quantum yield as a function of the exciting wavelength is determined in one experimental cycle. The discussion of the method is performed by measurements on fluorescein in aqueous solution. The results are compared to literature data. The conformity demonstrates the applicability of the new method.
Spatial Imaging Identification in a Fiber-Bundle Confocal Fluorescence Microspectrometer
Authors: Li Yao Qun , Sasaki Shin-Ya , Inoue Takanori , Harata Akira , Ogawa Teiichiro
Published: October 2003

We have developed a CCD-based fiber-bundle confocal fluorescence microspectrometer exhibiting a spectrum of individual fiber spots on the CCD. The development led to a new technique, spatial imaging identification, and revealed the sources of various signals based on the spatial distribution of a signal in the spectral images. The new technique allows for easy alignment of the optics and discrimination of various interference lights. The potential application to surface analysis is also emphasized.
Detection of Fibrilated Polymeric Contaminants in Wool and Cotton Yarns
Authors: Church J. S. , O'Neill J. A. , Woodhead A. L.
Published: October 2003

The contamination of natural fiber yarns with polymeric fibrils is a common problem in the textile industry. This work demonstrates that near-infrared spectroscopy in the 2250 to 2400 nm region is a viable technique for the detection of hydrocarbon-based polymeric contamination in both wool and cotton yarn samples. Both high-density polyethylene and polypropylene fibrils typical in size to those found in industry could be detected irrespective of polymer and yarn color. A principal component analysis model based on first-order derivative spectra was developed in which yarns contaminated with polymeric fibrils could easily be separated from pure wool yarns. The spectra obtained from the contaminated regions of the yarns were found to cluster well with spectra obtained from the pure polymeric materials. With the use of soft independent modeling for class analogy (SIMCA), a single class model for wool was developed on the basis of the raw data. This model easily discriminated between pure wool and polymer-containing samples, but the distinction between the different polymer types themselves was poor. This separation was enhanced, however, when the model was based on first-derivative spectra.
Modulated Reflectance Analysis of Complex Surface Structures
Authors: Rosen D. L. , Lambrakos S. G.
Published: October 2003

An analytical approach is presented for correlating modulated reflectance spectra and complex surface structure. A response function is constructed of specular reflectance from metal surfaces that are both rough and spatially dispersive. The method of analysis is based on a response function formulation that entails a windowing operation. This windowing operation is not ad hoc and is theoretically well founded for providing a statistical interpretation of the permittivity function. The initial analysis indicates that the windowing operation provides for a robust formulation that is conveniently adaptable to a wide range of frequencies, spanning regimes characterized by different response characteristics. A prototype case using this windowed response function formulation is applied to the electroreflectivity spectra, from 1.5 to 4.5 eV, of roughened silver electrodes. The electrode is modeled by a two-interface system as the basis of a parameterization of experimentally measured response functions, which are partitioned into reflectivity and transparent regimes by the windowing operation. The bulk plasmons and defect polaritons are characterized by our robust formulation. In addition, we present a discussion of the general significance of our approach with respect to the application of statistical pattern recognition to the analysis of modulated reflectivity data.
Near-Infrared Spectroscopy for Determination of Glucose, Lactate, and Ammonia in Cell Culture Media
Authors: McShane Michael J. , Coté Gerard L.
Published: October 2003

The potential for noninvasive determinations of glucose, lactate, and ammonia in cell culture media was investigated through near-infrared spectroscopy of the 2.0–2.5 μm combination region. Samples taken from a three-day fibroblast culture were analyzed with standard clinical chemistry techniques and with a Fourier transform infrared spectrometer. The data were analyzed in three phases in an attempt to solve problems of correlation in the data. First, partial least-squares regression was used to build a multivariate calibration model based on the near-infrared spectra of the cell culture media and measured reference values. Second, an independent calibration was performed with aqueous mixtures of glucose, lactate, ammonia, glutamate, and glutamine. Finally, a calibration using a combination of spectra from cell culture media samples and aqueous mixtures was performed. In each case, the spectral loadings obtained from the calibration were inspected to determine the extent of weighting given to different spectral regions. The results indicate that a selective calibration model can be produced by combining data from samples of different type. Prediction errors of 2, 8, and 15% were obtained for glucose, lactate, and ammonia, respectively.
Effect of Wavelength Drift on Single- and Multi-Instrument Calibration Using Genetic Regression
Authors: Ozdemir Durmus , Mosley Matt , Williams Ron
Published: October 2003

The ability of genetic regression (GR) to correct for wavelength drift in instrument responses was investigated in single- and multiinstrument calibrations. Sample spectra of ternary mixtures were collected on two near-infrared (NIR) spectrometers, one a dispersive instrument and one a Fourier transform instrument, with different resolutions. In the first and second cases, calibration models were generated with the use of spectra collected on a single instrument. For the third case, hybrid calibration models (HCMs) were built in order to combine spectra from two instruments into one calibration model. In order to simulate a wavelength shift, some of the spectra were shifted along the wavelength axis from 0 nm to 6 nm. The performance of GR was poor when calibration models produced from unshifted spectra were used to predict shifted spectra. However, the inclusion of shifted spectra in the calibration model corrected the prediction of shifted and unshifted spectra at levels similar to those of models built and evaluated by using only unshifted spectra.
Cluster Analysis of Gallstone FT-IR Spectra: Tests on Simulated Mixture Spectra and Comparison between Spectral and Morphological Classification of Human Gallstones
Authors: Laloum Eric , Dao Nguyen Quy , Daudon Michel
Published: October 2003

Sixty-four combination spectra of three major gallstone components [i.e., cholesterol, calcium bilirubinate, and calcium carbonate (aragonite)] were simulated in accordance with a “fractal” ternary diagram. Comparison between the original pattern of composition and factorial maps of pretreated spectra makes it possible to show the effects of different normalization procedures (Euclidean norm, spectrum maximum, and area under spectrum set to 1). Cluster analysis of these spectra, depending on different agglomerative links (single linkage, complete linkage, average linkage, and Ward's criterion), was carried out. All the resultant trees yield the same groups, but Ward's criterion best preserves the pattern of the data. More than 100 gallstones from France and Vietnam were classified by using cluster analysis of their FT-IR spectra with Ward's criterion. Seven homogeneous groups of spectra were extracted, which have been significantly correlated to the four morphological types of gallstones: pure cholesterol, mixed cholesterol, brown pigment, and black pigment stones. This analysis also reveals that the morphological groups are not homogeneous in composition, in particular for black pigment stones.
Friedel—Crafts Acylation on Porous Divinyl Benzene Polymer Particles: A Reaction Kinetic Process Studied by Mid- and Near-Infrared Spectroscopy
Authors: Christy Alfred A. , Nyhus Anne K. , Grung Bjørn , Kvalheim O. M. , Hagen Steinar , Schanche Jon S.
Published: October 2003

Porous poly(para-divinylbenzene) and poly(meta-divinylbenzene) particles were synthesized from para-divinylbenzene and meta-divinylbenzene monomers with toluene and 2-ethylhexanoic acid as porogens. The residual vinyl groups in the particles were thereafter reacted with lauroyl chloride by using the Friedel–Crafts reaction. The conversion of vinyl groups was followed by analyzing polymer particles taken from the reaction mixture at different time intervals. Infrared spectroscopy in both the mid- and near-infrared region was used as the analytical technique. The intensity changes in the overtone absorption at 1628 nm due to the vinyl bonds were used as the basis for the quantification of the reaction. Spectra of the particles in the mid-IR region provide understanding of the changes taking place in the polymer matrix during the acylation reaction. The results indicated that the reaction took place at a faster rate in the polymer particles synthesized from para-DVB monomer compared with the poly(meta-DVB) particles. The polymer particles synthesized with toluene as porogen react faster than the polymer particles prepared with 2-ethylhexanoic acid as the porogen. The analysis also indicated that the acylation takes place at the early stages of the reaction and the product formed transforms into more stable products at the latter stages. On the basis of the infrared analysis, mechanisms for the formation of the different products are proposed.
Surface-Site Charge-Displacement Model for Analysis of Electromodulated Optical Second-Harmonic Response at a Metal Surface
Authors: Lambrakos S. G. , Trzaskoma-Paulette P. P. , Triandaf I. A.
Published: October 2003

We present an analysis of second-harmonic (SH) response from metal surfaces that is based on a model representation whose associated parameters are defined in terms of nonlinear polarizabilities originating from charge displacement occurring on a molecular level. Our analysis suggests that the general functional dependence of SH response at a metal/electrolyte interface on the time-independent (dc) electric field is typically different from that implied by previous models. The analysis shows that our model representation is sufficiently general for extracting features from second-harmonic generation (SHG) data in order to analyze such data by methods based on system identification and pattern recognition. Our model, which is based on a classical representation of the nonlinear response of bound (or constrained) charge, is found to be consistent with trends observed in experimental measurements of second-harmonic response as a function of surface charge density. The results of this analysis suggest that SH data are relatively rich in terms of features that can be correlated with local surface structure and that the data should be interpreted by means of a more general model representation than has been previously proposed.
Near-Field Raman Spectral Measurement of Polydiacetylene
Authors: Narita Yoshihito , Tadokoro Toshiyasu , Ikeda Teruki , Saiki Toshiharu , Mononobe Syuji , Ohtsu Motoichi
Published: October 2003

Two-dimensional near-field Raman spectra and topographic images of the polydiacetylene surface are measured simultaneously by using a near-field Raman spectrometer. The spectra (located 100 nm apart) have different spectral features. The peak intensity ratio of two C=C peaks at 1520 and 1457 cm−1 does not correlate with the topographic image and shows differences in the subwavelength scale. These differences can be interpreted as spatial differences in the number of successive bonds on the polydiacetylene surface. In contrast, the near-field Raman intensity of the C=C bond at 1457 cm−1 correlates strongly with the topographic image. This phenomenon can be interpreted as a change in the efficiency of collecting Raman scattering light.
Hyperspectral Raman Microscopic Imaging Using Powell Lens Line Illumination
Authors: Christensen Kenneth A. , Morris Michael D.
Published: October 2003

The design and characterization of a simple and robust hyperspectral Raman line imaging illumination system with the use of a Powell lens is reported. The generated line uniformity is ±5% of total intensity with a laser power density of 12 mW/μm2 at the sample with a 50×/0.8 NA (numerical aperture) objective. Similar results were obtained by using other objectives. Linewidths remained near the diffraction limit for all objectives tested. Significant decreases in image acquisition time are also reported with the use of a Powell lens-illuminated hyperspectral Raman line imaging microscope equipped with an intensified charge-coupled device (CCD) detector. Hyperspectral images (100 × 350 pixels) were acquired in as little as 8 with a corresponding signal-to-noise ratio of 24.
Spectroscopic Characterization of Laser-Ablated Plume from a La—Ca—Mn—O Target in an O2 Ambient
Authors: Dang Hai-Jun , Zhou Ming-Fei , Qin Qi-Zong
Published: October 2003

The composition and evolution of the plume produced by the laser ablation of a La2O3–CaO–MnO2 target at 355 nm in an O2 ambient have been studied with a temporally and spatially resolved optical emission spectroscopic technique. Besides lines of excited metal atoms and ions, such as La(II), Ca(II), Mn(II), Ca(I), and Mn(I), bands of the metal oxides LaO and MnO were observed. In the oxygen ambient, two emission peaks corresponding to a fast and a slow component of ablated species Mn(I), MnO, Ca(I), and LaO were measured by optical time-of-flight spectroscopy. The delay times of two emission components for these ablated species were investigated as a function of the observation distance from the target surface and the laser fluence. The possible mechanism of the laser-ablated plume is discussed.
Study of Amorphous MoS2 Films Grown by Pulsed Laser Deposition
Authors: McDevitt N. T. , Bultman J. E. , Zabinski J. S.
Published: October 2003

The amorphous structure of MoS2 lms prepared by pulsed laser deposition (PLD) has been evaluated with the use of Raman and X-ray photoelectron spectroscopy (XPS). The initial study of the room-temperature deposited films indicated a featureless Raman spectrum. On closer examination, however, four weak reproducible bands were observed. There has been some confusion in the literature as to the nature of this spectrum—whether it represents an amorphous MoS3 structure or a mixture of MoS2 and sulfur. Our interpretation of the Raman and XPS data indicates that the laser-deposited films represent a mixture of small domains of MoS2 and amorphous sulfur.
Low-Cost, Modular Electrothermal Vaporization System for Inductively Coupled Plasma Atomic Emission Spectrometry
Authors: Levine Keith , Wagner Karl A. , Jones Bradley T.
Published: October 2003

In this investigation, commercially available tungsten filaments were employed to electrothermally vaporize liquid samples prior to their introduction into an inductively coupled plasma (ICP). These filaments were extracted from standard 150 W slide projector bulbs. The temperature of the tungsten coil was controlled by supplying a desired current at 120 V ac. A small sample volume, typically 20 μL, was manually pipetted onto the coil and dried at a 2.3 A current. At the conclusion of this dry step, a 7.4 A atomization current was applied, and sample atoms were sputtered off the coil and rapidly introduced into the plasma as a dense plug by a flow of Ar/H2 gas. A charge-coupled device (CCD) array detector allowed for multielement determinations. Simultaneously collected data are presented for Ag, Ba, Be, Cd, Cu, Fe, Mn, Pb, Sr, and Zn. Many of these test elements are of biological importance either as cumulative poisons or as essential nutrients. Each also possesses one or more strong ICP emission lines in the spectral range of the CCD detector. The utility of this inexpensive electrothermal vaporization (ETV)-ICP method is evaluated for botanical and biological samples through the use of standard reference materials (NIST SRM 1547 “Peach Leaves” and NIST SRM 1566a “Oyster Tissue”).