bluuebunny/crossref_metadata_2025 huggingface dataset:
Moving Window Two-Dimensional Correlation Spectroscopy and Determination of Signal-To-Noise Threshold in Correlation Spectra
Authors: Šašić Slobodan , Ozaki Yukihiro
Published: October 2003

In this paper we report two new developments in two-dimensional (2D) correlation spectroscopy; one is the combination of the moving window concept with 2D spectroscopy to facilitate the analysis of complex data sets, and the other is the definition of the noise level in synchronous/asynchronous maps. A graphical criterion for the latter is also proposed. The combination of the moving window concept with correlation spectra allows one to split a large data matrix into smaller and simpler subsets and to analyze them instead of computing overall correlation. A three-component system that mimics a consecutive chemical reaction is used as a model for the illustration of the two ideas. Both types of correlation matrices, variable–variable and sample–sample, are analyzed, and a very good agreement between the two is met. The proposed innovations enable one to comprehend the complexity of the data to be analyzed by 2D spectroscopy and thus to avoid the risks of over-interpretation, liable to occur whenever improper caution about the number of coexisting species in the system is taken.
Near-Infrared Spectroscopic Monitoring of a Series of Industrial Batch Processes Using a Bilinear Grey Model
Authors: Van Sprang Eric N. M. , Ramaker Henk-Jan , Westerhuis Johan A. , Smilde Age K. , Gurden Stephen P. , Wienke Dietrich
Published: October 2003

A good process understanding is the foundation for process optimization, process monitoring, end-point detection, and estimation of the end-product quality. Performing good process measurements and the construction of process models will contribute to a better process understanding. To improve the process knowledge it is common to build process models. These models are often based on first principles such as kinetic rates or mass balances. These types of models are also known as hard or white models. White models are characterized by being generally applicable but often having only a reasonable fit to real process data. Other commonly used types of models are empirical or black-box models such as regression and neural nets. Black-box models are characterized by having a good data fit but they lack a chemically meaningful model interpretation. Alternative models are grey models, which are combinations of white models and black models. The aim of a grey model is to combine the advantages of both black-box models and white models. In a qualitative case study of monitoring industrial batches using near-infrared (NIR) spectroscopy, it is shown that grey models are a good tool for detecting batch-to-batch variations and an excellent tool for process diagnosis compared to common spectroscopic monitoring tools.
Emission Spectroscopy for Coal-Fired Cyclone Furnace Diagnostics
Authors: Wehrmeyer Joseph A. , Boll David E. , Smith Richard
Published: October 2003

Using a spectrograph and charge-coupled device (CCD) camera, ultraviolet and visible light emission spectra were obtained from a coal-burning electric utility's cyclone furnaces operating at either fuel-rich or fuel-lean conditions. The aim of this effort is to identify light emission signals that can be related to a cyclone furnace's operating condition in order to adjust its air/fuel ratio to minimize pollutant production. Emission spectra at the burner and outlet ends of cyclone furnaces were obtained. Spectra from all cyclone burners show emission lines for the trace elements Li, Na, K, and Rb, as well as the molecular species OH and CaOH. The Ca emission line is detected at the burner end of both the fuel-rich and fuel-lean cyclone furnaces but is not detected at the outlet ends of either furnace type. Along with the disappearance of Ca is a concomitant increase in the CaOH signal at the outlet end of both types of furnaces. The OH signal strength is in general stronger when viewing at the burner end rather than the exhaust end of both the fuel-rich and fuel-lean cyclone furnaces, probably due to high, non-equilibrium amounts of OH present inside the furnace. Only one molecular species was detected that could be used as a measure of air/fuel ratio: MgOH. It was detected at the burner end of fuel-rich cyclone furnaces but not detected in fuel-lean cyclone furnaces. More direct markers of air/fuel ratio, such as CO and O2 emission, were not detected, probably due to the generally weak nature of molecular emission relative to ambient blackbody emission present in the cyclone furnaces, even at ultraviolet wavelengths.
Liquid/Liquid Optical Waveguides Using Sheath Flow as a New Tool for Liquid/Liquid Interfacial Measurements
Authors: Takiguchi Hiromi , Odake Tamao , Ozaki Manabu , Umemura Tomonari , Tsunoda Kin-Ichi
Published: October 2003

A liquid/liquid optical waveguide was constructed using a sheath flow. Since the refractive index of an organic solvent is generally higher than that of water ( nD = 1.33), light introduced into the inner organic flow should proceed with total multi-reflection within the inner flow, so that the inner part of the sheath flow acts as the core of an optical waveguide. This sheath flow liquid/liquid optical waveguide was stable and showed no substantial background scattering. Moreover, it is applicable to both miscible and immiscible liquid/liquid interfaces. Thus, it may become a new tool for studying liquid/liquid interfaces as well as for sensitive optical measurements.
Time-Resolved Fourier Transform Infrared Spectroscopic Imaging
Authors: Bhargava Rohit , Levin Ira W.
Published: October 2003

Fourier transform infrared (FT-IR) imaging allows simultaneous spectral characterization of large spatial areas due to its multichannel detection advantage. The acquisition of large amounts of data in the multichannel configuration results, however, in a poor temporal resolution of sequentially acquired data sets, which limits the examination of dynamic processes to processes that have characteristic time scales of the order of minutes. Here, we introduce the concept and instrumental details of a time-resolved infrared spectroscopic imaging modality that permits the examination of repetitive dynamic processes whose half-lives are of the order of milliseconds. As an illustration of this implementation of step-scan FT-IR imaging, we examine the molecular responses to external electric-field perturbations of a microscopically heterogeneous polymer–liquid crystal composite. Analysis of the spectroscopic data using conventional univariate and generalized two-dimensional (2D) correlation methods emphasizes an additional capability for accessing of simultaneous spatial and temporal chemical measurements of molecular dynamic processes.
New Opportunities in Micro- and Macro-Attenuated Total Reflection Infrared Spectroscopic Imaging: Spatial Resolution and Sampling Versatility
Authors: Chan K. L. A. , Kazarian S. G.
Published: October 2003

New opportunities exist to obtain chemical images using attenuated total reflection infrared (ATR-IR) spectroscopy. This paper shows the feasibility of obtaining FT-IR images with a spatial resolution of at least 3–4 μm using a Ge ATR objective coupled with an infrared microscope. The improved spatial resolution compared to FT-IR images obtained by the transmission method is due to the high refractive index of the ATR crystal, which gives a high numerical aperture and hence, a higher spatial resolution. FT-IR imaging with a conventional diamond ATR accessory has been investigated. This is the first time that FT-IR imaging is reported using such a versatile accessory based on a diamond ATR crystal. These results showed that a spatial resolution up to 13 μm can be achieved without the use of infrared microscope objectives. One advantage of the diamond element is that it allows pressure to be applied and hence, good contact to be obtained over the whole field of view.
Stress-Induced Plasma Volume Change Determined Using Plasma FT-IR Spectra
Authors: Petibois Cyril , Déléris Gérard
Published: October 2003

Our purpose was to determine the plasma-volume (PV) change induced by a physical stress independent of the metabolic events that may interfere with physiological fluid shifts in to and out of the intravascular space. Our methods included using 178 exercise tests of varying duration and intensity for determination of PV change during exercise. Plasma Fourier transform infrared (FT-IR) spectra were used to compare hematocrit change to the total spectral area (4000–500 cm−1) and the protein and albumin concentration changes induced by exercise. Our results showed that exercise induced a raise in protein (+10.4 ± 3.1%) and albumin (+9.8 ± 3.3%) concentrations that significantly correlated with PV change (14.1 ± 5.2% of plasma volume; P = 0.05 with protein and albumin concentration changes). However, evolution of the total spectral area obtained from rest-plasma (524 ± 21 a.u.) and exercise-plasma (611 ± 26 a.u.; +14.1 ± 4.8%) FT-IR spectra showed a higher correlation level with PV change ( r = 0.98; P = 0.005; Sx/y = 1.26 a.u.). It is our conclusion that although exercise-induced changes in protein and albumin concentrations were found to correlate with PV change, the use of the total spectral area of the plasma FT-IR spectra allowed a more precise measurement of PV change.
Determination of Hydrocarbons Using Sapphire Fibers Coated with Poly(Dimethylsiloxane)
Authors: Howley Rhona , MacCraith B. D. , O'Dwyer Kieran , Masterson Hugh , Kirwan P. , McLoughlin Peter
Published: October 2003

A poly(dimethylsiloxane) (PDMS) coated sapphire fiber has been investigated as a sensor for hydrocarbons (HCs) in the mid-infrared region around 3000 cm−1. In order to optimize and predict sensor response, the diffusion behavior of the analytes into the PDMS preconcentration medium has been examined. A diffusion model based on Fickian diffusion was used to quantify diffusion. The model incorporated such factors as film thickness, refractive index of the polymer and the fiber core, and principal wavelength at which the analyte absorbs. A range of hydrocarbons, from hexane to pentadecane, was analyzed at 2930 cm−1 using both fiber-coupled Fourier transform infrared spectroscopy and a modular prototype system. Diffusion coefficients were determined for these compounds and diffusion behavior examined and related to factors such as analyte polarity and molecular size. The diffusion coefficients were found to range from 6.41 × 10−11 ± 5 × 10−12 to 5.25 × 10−11 ± 9 × 10−13 cm2 s−1 for hexane and pentadecane into a 2.9 μm PDMS film, respectively. The diffusion model was also used to examine the effect of changing system parameters such as film thickness in order to characterize sensor response.
Rapid, Noninvasive Quantitative Determination of Acyclovir in Pharmaceutical Solid Dosage Forms through Their Poly(Vinyl Chloride) Blister Package by Solid-State Fourier Transform Raman Spectroscopy
Authors: Skoulika Stavroula G. , Georgiou Constantinos A.
Published: October 2003

Fourier transform (FT) Raman spectroscopy based on band intensity or band area measurements was used for the quantitative determination of acyclovir in pharmaceutical solid dosage forms through their poly(vinyl chloride) blister package. Univariate calibration using the bands observed at 1690, 1630, 1574, 1482, 1181, 578, and 508 cm−1 was found to be sufficient for the analysis. Calibration curves were linear, the correlation coefficients being 0.997–0.9993 and 0.996–0.9991 for band intensity and band area measurements, respectively. Results obtained compare well, as indicated by the t-test, with those obtained by the current United States Pharmacopoeia (USP 24) and National Formulary (NF 19) method. Precision ranged from 0.7–4.5 and 0.4–4.0% RSD ( n = 3) for band intensity and band area measurements, respectively. The developed nondestructive FT-Raman method is rapid, simple, and can be used for the on-line, real-time monitoring of acyclovir formulation production lines.
Structural Analysis of Triacylglycerols and Edible Oils by Near-Infrared Fourier Transform Raman Spectroscopy
Authors: Weng Yih-Ming , Weng Ru-Hui , Tzeng Chin-Yin , Chen Wenlung
Published: October 2003

Fourier transform Raman spectroscopy was employed for structural analysis of triacylglycerols and edible oils. Raman spectra sensitively reflected structural changes in oils. Even slight structural fluctuation between triacylglycerols and free fatty acids led to obvious differences in Raman bands as shown by C–O–C stretching from 800 to 1000 cm−1 and the band at 1742 cm−1. Structural difference in geometric isomers was easily distinguished as proved by C = C stretching at 1655 cm−1 ( cis) shifting to 1668 cm−1 ( trans) and by =C–H in-plane bending at 1266 cm−1 in cis disappearing in the trans isomer. Raman intensity at 1266, 1302, and 1655 cm−1 changed concomitantly with the change of double-bond content in oils. It showed that FT-Raman was capable of precisly reflecting the content of double bonds in oils. A linear correlation with high consistency between the Raman intensity ratio ( v1655 /v1444) and the iodine value was obtained for commercial oils. Based on the results, FT-Raman spectroscopy proved itself a simple and rapid technique for oil analysis since each measurement could be directly completed in 3 min without any sample modifications.
Optimizing Detection Sensitivity on Surface-Enhanced Raman Scattering of Transition-Metal Electrodes with Confocal Raman Microscopy
Authors: Ren Bin , Lin Xu-Feng , Jiang Yu-Xiong , Cao Pei-Gen , Xie Yong , Huang Qun-Jian , Tian Zhong-Qun
Published: October 2003

Some points on how to improve the detection sensitivity of confocal Raman microscopy for the study of surface-enhanced Raman scattering (SERS) of transition-metal electrodes are discussed, including the careful design of the spectroelectrochemical cell, proper selection of the thickness of the solution layer, the binning of charge-coupled device (CCD) pixels, and appropriate setting of the notch filter. Various roughening methods for the Pt, Rh, Fe, Co, and Ni electrode surfaces have been introduced in order to obtain SERS-active surfaces. It has been shown that the appropriate roughening procedure and the optimizing performance of the confocal Raman microscope are the two most important factors to directly generate and observe SERS on net transition-metal electrodes.
Use of a Sample Translation Technique to Minimize Adverse Effects of Laser Irradiation in Surface-Enhanced Raman Spectrometry
Authors: De Jesús M. A. , Giesfeldt K. S. , Sepaniak M. J.
Published: October 2003

Surface-enhanced Raman spectroscopy (SERS) has proven to be a very powerful tool in the analysis of a wide range of compounds. However, continuous irradiation of the laser beam over the SERS substrate can promote the gross decomposition of the sample analytes and significantly broaden and diminish the intensities of observed spectral bands. In addition, the incident radiation can promote thermal or photolytic fragmentation of analytes, thereby altering the observable bands and possibly leading to a misinterpretation of analytical data. Finally, chemical or morphological changes in the SERS substrate are possible. This work presents the use of a sample translation technique (STT) as a means to minimize these adverse effects. By spinning the sample rapidly, the effective residence time of analytes and substrate within the irradiated zone is dramatically decreased without reduction of spectral acquisition time or the density of analyte in the zone. The technique is studied by acquiring SERS spectra of Naproxen USP, riboflavin, folic acid, Rhodamine 6G, and 4-aminothiophenol using silver islands on glass and silver–poly(dimethylsiloxane) composite substrates under various spinning and stationary conditions. In all cases, spectra show improvements upon spinning at laser powers as low as 4.2 (±0.1) mW. Specific differences in the appearance of the spectra and the potential use of STT for improved SERS qualitative and quantitative determinations are presented.
Monitoring the Formation and Decay of Transient Photosensitized Intermediates Using Pump-Probe UV Resonance Raman Spectroscopy. I: Self-Modeling Curve Resolution
Authors: Kleimeyer James A. , Harris Joel M.
Published: October 2003

Resolution of transient excited-state Raman scattering from ground-state and solvent bands is a challenging spectroscopic measurement since excited-state spectral features are often of low intensity, overlapping the dominant ground-state and solvent bands. The Raman spectra of these intermediates can be resolved, however, by acquiring time-resolved data and using multidimensional data analysis methods. In the absence of a physical model describing the kinetic behavior of a reaction, resolution of the pure-component spectra from these data can be accomplished using self-modeling curve resolution, a factor analysis technique that relies on the correlation in the data along a changing composition dimension to resolve the component spectra. A two-laser UV pump-probe resonance-enhanced Raman instrument was utilized to monitor the kinetics of amine quenching of excited-triplet states of benzophenone. The formation and decay of transient intermediates were monitored over time, from 15 ns to 100 μs. Factor analysis of the time-resolved spectral data identified three significant components in the data. The time-resolved intensities at each Raman wavenumber shift were projected onto the three significant eigenvectors, and least-squares criteria were developed to find the common plane in the space of the eigenvectors that includes the observed data. Within that plane, the three pure-component spectra were resolved using geometric criteria of convex hull analysis. The resolved spectra were found to arise from benzophenone excited-triplet states, diphenylketyl radicals, and the solvent and ground-state benzophenone.
Monitoring the Formation and Decay of Transient Photosensitized Intermediates Using Pump-Probe UV Resonance Raman Spectroscopy. II: Kinetic Modeling and Multidimensional Least-Squares Analysis
Authors: Kleimeyer James A. , Harris Joel M.
Published: October 2003

Analysis of transient excited-state Raman spectra is a challenging spectroscopic measurement since transient spectral features are often overlapped with dominant ground-state and solvent bands. In the previous manuscript, resolution of component Raman spectra from the time-resolved amine quenching of excited-triplet benzophenone was accomplished using self-modeling curve resolution, a model-free factor analysis technique that relies on correlation in the data along a changing composition dimension. The results are consistent with the production of diphenylketyl radicals by H-atom abstraction from the amine and subsequent free-radical decay by recombination reactions. A kinetic model for this chemistry is developed in the present work, based on the observed Raman scattering data and the structures of product species confirmed by mass spectral analysis. The model is applied to the analysis of the time-dependent Raman scattering data using multidimensional least-squares methods, and it yielded well-resolved spectra of benzophenone excited-triplet states, diphenyl ketyl radical, and the solvent and ground-state precursors. The best-fit kinetic parameters agree well with the time-dependent triplet-state and ketyl-radical concentration profiles.
Multiphoton Ionization Mass Spectrometry of Chlorophenols as Indicators for Dioxins
Authors: Uchimura Tomohiro , Hafner Klaus , Zimmermann Ralf , Imasaka Totaro
Published: October 2003

Mono-, di- and trichlorophenols were measured using resonance-enhanced multiphoton ionization mass spectrometry (MPI-MS) combined with supersonic jet (SSJ) or effusive molecular beam (EMB) spectrometry. All mono- and dichlorophenols, except 2,6-dichlorophenol, provided sharp and structured MPI spectra for the S1←S0 transition. Selectivity and sensitivity were both enhanced when SSJ spectrometry was used, compared with EMB spectrometry, because of a narrower linewidth in the MPI spectrum, given by molecular cooling by supersonic jet expansion. The ionization efficiency decreased with increasing number of chlorine substituents for the chlorophenols, since they have shorter excited-state lifetimes and require three photons for ionization. Some of the chlorophenols, which are toxic themselves, have the potential for use as indicators for analysis of polychlorinated dibenzo- p-dioxin/dibenzofurans in flue gases emitted from an incinerator.
Sugar Interaction with Metals in Aqueous Solution: Indirect Determination from Infrared and Direct Determination from Nuclear Magnetic Resonance Spectroscopy
Authors: Rondeau Philippe , Sers Sandrine , Jhurry Dhanjay , Cadet Frederic
Published: October 2003

In this article, mid-infrared Fourier transform (Mid-FT-IR) and carbon thirteen nuclear magnetic resonance (13C NMR) spectroscopy have been used to determine possible interactions between sucrose and various alkali or alkaline earth metals in aqueous solution. In the presence of these metals, significant shifts in the absorption bands of sucrose were noted by mid-FT-IR coupled with principal component analysis (PCA). These shifts were explained on the basis of weakening of the H-bond network between sucrose and water and possible interactions between sucrose and the metal ion. Factorial maps were established and the spectral patterns obtained show that these interactions vary according to the nature of the metal ion. 13C NMR analysis showed that the carbon atoms of sucrose undergo shielding or deshielding in the presence of metal ions in aqueous solutions. Two factors were invoked to account for the variation of chemical shifts: the rupture of hydrogen bonds due to hydration of the metal ion and the possible coordination of the metal ion to the oxygen atoms of sucrose.
Improved Piecewise Orthogonal Signal Correction Algorithm
Authors: Feudale Robert N. , Tan Huwei , Brown Steven D.
Published: October 2003

Piecewise orthogonal signal correction (POSC), an algorithm that performs local orthogonal filtering, was recently developed to process spectral signals. POSC was shown to improve partial least-squares regression models over models built with conventional OSC. However, rank deficiencies within the POSC algorithm lead to artifacts in the filtered spectra when removing two or more POSC components. Thus, an updated OSC algorithm for use with the piecewise procedure is reported. It will be demonstrated how the mathematics of this updated OSC algorithm were derived from the previous version and why some OSC versions may not be as appropriate to use with the piecewise modeling procedure as the algorithm reported here.
Laser-Induced Breakdown Spectroscopy Detection and Classification of Biological Aerosols
Authors: Hybl John D. , Lithgow Gregg A. , Buckley Steven G.
Published: October 2003

Laser-induced breakdown spectroscopy (LIBS) is examined as a potential method for detecting airborne biological agents. A spectrally broadband LIBS system was used for laboratory measurements on some common biological agent simulants. These measurements were compared to those of common, naturally occurring biological aerosol components (pollen and fungal spores) to determine the potential of LIBS for discriminating biological agents from natural background aerosols. A principal components analysis illustrates that linear combinations of the detected atomic lines, which are present in different ratios in each of the samples tested, can be used to discriminate biological agent simulants from other biological matter. A more sensitive, narrowband LIBS instrument was used to demonstrate the detection of single simulant (Bg) particles in the size range 1–5 μm. Ca, Mg, and Na, which are present in varying concentrations between 0.3 and 11% (by mass) in the Bg particles, were observed in single particles using LIBS.
Luminescent Lanthanide Chelate Contrast Agents and Detection of Lesions in the Hamster Oral Cancer Model
Authors: Bornhop Darryl J. , Griffin John M. M. , Goebel Timothy S. , Sudduth Mark R. , Bell Brent , Motamedi Massoud
Published: October 2003

Lanthanide chelates are a somewhat unique class of molecules that have proven to be useful in the biomedical field due to their extremely large Stokes' shift and long fluorescent lifetimes. The ability of these molecules to produce fluorescence in the low- or zero-background regime makes this class of molecules excellent candidates for use as contrast agents for a wide variety of applications in biological settings. Here we present the preparation, spectroscopic characterization, and application of a new terbium chelate contrast agent, based on the 1,4,7,10-tetraazacyclododecane macrocycle (cyclen), for detection of early-stage malignant lesions in the Syrian hamster cheek pouch. Tb-P(CTMB) delivers bright blue-green luminescence when excited with low photon fluxes of UV light. As a pilot study, the DMBA-treated Golden Hamster Cheek pouch epithelial cancer model was employed and Tb-P(CTMB) was used as a topical agent for the visual detection of diseased tissue. In this preliminary study the agent tended to associate with early-stage malignant lesions, suggesting that Tb-P(CTMB) could be used as a contrast agent to aid in identifying early-stage oral cancer lesions.
Temperature-Dependent Near-Infrared Spectra of Bovine Serum Albumin in Aqueous Solutions: Spectral Analysis by Principal Component Analysis and Evolving Factor Analysis
Authors: Yuan Bo , Murayama Koichi , Wu Yuqing , Tsenkova Roumiana , Dou Xiaoming , Era Seiichi , Ozaki Yukihiro
Published: October 2003

Fourier transform near-infrared (FT-NIR) spectra have been measured for bovine serum albumin (BSA) in an aqueous solution (pH 6.8) with a concentration of 5.0 wt % over a temperature range of 45–85 °C. Not only conventional spectral analysis methods, such as second-derivative spectra and difference spectra, but also chemometrics, such as principal component analysis (PCA) and evolving factor analysis (EFA), have been employed to analyze the temperature-dependent NIR spectra in the 7500–5500 and 4900–4200 cm−1 regions of the BSA aqueous solution. Intensity changes of bands in the 7200–6600 cm−1 and 4650–4500 cm−1 regions in the difference spectra indicate variations of the hydration and secondary structure of BSA in the aqueous solution, respectively. The plot of a band intensity at 7080 cm−1 in the different spectra shows a clear turning point at 63 °C, revealing that a significant change in the hydration occurs at about 63 °C. The forward and backward eigenvalues (EVs) from EFA suggest that marked changes in the hydration and secondary structure of BSA take place in the temperature ranges of 61–65 °C and 59–63 °C, respectively. In addition, the temperature of 71 °C marked in the EFA plots may correspond to the onset temperature of increase in the intermolecular β-sheet structure.
Near-Infrared Spectroscopic Measurement of Urea in Dialysate Samples Collected during Hemodialysis Treatments
Authors: Eddy Christopher V. , Flanigan Michael , Arnold Mark A.
Published: October 2003

Single-beam spectra were collected over the combination region of the near-infrared spectrum for 80 samples collected from 15 people over a two-week period. Partial least-squares (PLS) regression was used to generate an optimized calibration model for urea. PLS calibration models accurately measure urea in the spent dialysate matrix. Prediction errors are on the order of 0.15 mM, which is sufficient for the clinical assessment of the dialysis process. In addition, the feasibility of a global calibration model is demonstrated by generating a calibration model from samples and spectra obtained from 12 people to predict the level of urea in samples collected from 3 different people. In this case, the standard error of prediction is 0.09 mM. Spectra were modified in order to systematically examine the impact of resolution and noise. Little impact is observed by altering the spectral resolution from 4 to 32 cm−1. Spectral noise, however, plays an important role in the accuracy of these calibration models. Increasing the magnitude of the spectral noise increases the prediction errors and increases the width of the spectral range necessary for extracting the analytical information. The utility of the method is demonstrated by analyzing dialysate samples collected during actual dialysis treatments. In addition, the necessary resolution and spectral quality necessary for reliable on-line urea monitoring is identified. These findings indicate that a dedicated, on-line urea spectrometer must posses a resolution of 16 cm−1 coupled with a sample thickness of 1.5 mm and spectral noise levels on the order of 25 micro-absorbance units when measured as the root-mean-square (RMS) noise of 100% lines.
In Vivo Noninvasive Measurement of Blood Glucose by Near-Infrared Diffuse-Reflectance Spectroscopy
Authors: Maruo Katsuhiko , Tsurugi Mitsuhiro , Tamura Mamoru , Ozaki Yukihiro
Published: October 2003

This paper reports in situ noninvasive blood glucose monitoring by use of near-infrared (NIR) diffuse-reflectance spectroscopy. The NIR spectra of the human forearm were measured in vivo by using a pair of source and detector optical fibers separated by a distance of 0.65 mm on the skin surface. This optical geometry enables the selective measurement of dermis tissue spectra due to the skin's optical properties and reduces the interference noise arising from the stratum corneum. Oral glucose intake experiments were performed with six subjects (including a single subject with type I diabetes) whose NIR skin spectra were measured at the forearm. Partial least-squares regression (PLSR) analysis was carried out and calibration equations were obtained with each subject individually. Without exception among the six subjects, the regression coefficient vectors of their calibration models were similar to each other and had a positive peak at around 1600 nm, corresponding to the characteristic absorption peak of glucose. This result indicates that there is every possibility of glucose detection in skin tissue using our measurement system. We also found that there was a good correlation between the optically predicted values and the directly measured values of blood samples with individual subjects. The potential of noninvasive blood glucose monitoring using our methodology was demonstrated by the present study.
Increasing Detectivity of Polarization Modulation Infrared Reflection—Absorption Spectroscopy for the Study of Ultrathin Films Deposited on Various Substrates
Authors: Saccani J. , Buffeteau T. , Desbat B. , Blaudez D.
Published: October 2003

In this paper, we present a simple way to increase the sensitivity of polarization modulation infrared reflection–absorption spectroscopy (PM-IRRAS) for the study of ultrathin films deposited on dielectric and semiconductor substrates. The enhancement of the absorption band intensity is obtained by reducing the signal arising from the substrate. This is achieved by adding a polarizer after the sample in order to balance the polarized reflectivities of the sample. As a consequence, the contribution of the film to the PM-IRRAS signal is increased relative to that of the substrate. An enhancement factor of about 10 has been obtained for ultrathin organic films deposited on glass and spread at the air–water interface. This method has also allowed the study of the very thin native oxide layer present on silicon without the need for the reference spectrum of bare silicon.
Adsorption of Methylene Blue onto Silylated Silica Surfaces, Studied Using Visible Attenuated Total Reflection Spectroscopy with a Slab Optical Waveguide
Authors: Tsunoda Kin-Ichi , Umemura Tomonari , Ueno Hiroko , Okuno Eriko , Akaiwa Hideo
Published: October 2003

The behavior of methylene blue (MB) molecules at silica/water and silylated silica/water interfaces was examined using visible attenuated total reflection spectroscopy with a slab optical waveguide (SOWG). An alkyl silane coating changed the adsorbed form of MB on the surface from a dimer (λmax = 600 nm, bare silica surface) to a monomer (λmax = 670 nm), and the carbon number of the silylation reagent influenced the amount of adsorption and the orientation of the molecule. Moreover, the addition of an anionic surfactant, dodecylbenzenesulfonate (DBS), caused the deposition of MB/DBS ion pairs, which gave an identical attenuated total reflection (ATR) spectrum to that of the dimer. Linear dichroism measurements revealed that the ion pairs were adsorbed onto the silylated silica surface randomly in terms of the orientation angle of MB, while the MB monomer was strongly oriented, i.e., the direction of the transition moment of MB roughly parallels the surface plane. This difference in the orientation angles of the adsorbed species can be utilized for their selective detection using polarization SOWG measurements.
Differential Thermal Lensing in Extended Samples
Authors: Marcano A. O. , Hung J. , Rodríguez L. , Borrero L.
Published: October 2003

We present a new scheme for a pump-probe mode-mismatched thermal lensing experiment aimed at extracting the value of low-absorbing components in the presence of a high-absorbing background. The method allows for the use of large path-length samples. Changes in the background absorption of a column of ethanol of 20 cm of 1% and a pollutant concentration detection limit of 0.04 ppm are obtained when using a pump light power of 34 mW.
Slag Analysis with Laser-Induced Breakdown Spectrometry
Authors: Kraushaar M. , Noll R. , Schmitz H.-U.
Published: October 2003

Laser-induced breakdown spectrometry (LIBS) has been applied for multi-elemental analysis of slag samples from a steel plant. In order to avoid the time-consuming step of sample preparation, the liquid slag material can be filled in special probes. After cooling of the liquid slag and solidification, the samples can be analyzed with LIBS. Chemical analysis of slag is an essential input parameter used for numerical simulations to control liquid steel processing. The relative variation range of element concentrations in slag samples from steel production can amount to up to 30%. A multivariate calibration model is used to take into account matrix effects caused by these varying concentrations. By optimizing the measuring parameters as well as the calibration models, an agreement between the standard X-ray fluorescence (XRF) analysis and LIBS analysis in terms of the coefficient of determination r2 of 0.99 for the main analytes CaO, SiO2, and Fetot of converter slag samples was achieved. The average repeatability of the LIBS measurement for these elements in terms of the relative standard deviation of the determined concentration is improved to less than 1.0%. With these results, the basis is established for future on-line applications of LIBS in the steel-making industry for slag analysis.
High-Temperature and High-Pressure Cubic Zirconia Anvil Cell for Raman Spectroscopy
Authors: Chen Jinyang , Zheng Haifei , Xiao Wansheng , Zeng Yishan
Published: October 2003

A simple and inexpensive cubic zirconia anvil cell has been developed for the performance of in situ Raman spectroscopy up to the conditions of 500 °C and 30 kbar pressure. The design and construction of this cell are fully described, as well as its applications for Raman spectroscopy. Molybdenum heater wires wrapped around ceramic tubes encircling two cubic zirconia anvils are used to heat samples, and the temperatures are measured and controlled by a Pt–PtRh thermocouple adhered near the sample chamber and an intelligent digital control apparatus. With this cell, Raman spectroscopic measurements have been satisfactorily performed on water at 6000 bar pressure to 455 °C and on ice of room temperature to 24 kbar, in which the determinations of pressures make use of changes of the A1 Raman modes of quartz and the shift of the sharp-line (R-line) luminescence of ruby, respectively.
Feasibility Study of Raman Spectroscopy as a Tool to Investigate the Liquid-Phase Chemistry of Aliphatic Organic Peroxides
Authors: Jacob Peter , Wehling Bernhard , Hill Wieland , Klockow Dieter
Published: October 2003

The described investigations are focused on peroxides occurring as products in atmospheric chemical processes, namely, hydrogen peroxide, methylhydroperoxide, hydroxymethylhydroperoxide, bis-(hydroxymethyl)peroxide, 1-hydroxyethylhydroperoxide, bis-(hydroxyethyl)peroxide, and hydroxymethylmethylperoxide. The compounds are identified and determined through the position and intensity of their characteristic O–O stretching bands in the range between 767 and 878 cm−1. Time-resolved Raman spectroscopy of peroxide solutions permits the in situ investigation of pathways and kinetics of reactions between peroxides and aldehydes.
UV Raman Microspectroscopy: Spectral and Spatial Selectivity with Sensitivity and Simplicity
Authors: Pajcini Vasil , Munro Calum H. , Bormett Richard W. , Witkowski Robert E. , Asher Sanford A.
Published: October 2003

The high sensitivity, selectivity, spatial resolution, and ease of operation of UV Raman microspectr oscopy is demonstrated with the use of a new highly efficient UV Raman microspectrometer with excitation at 244 nm. Single spectrograph dispersion combined with special new filters for the rejection of Rayleigh scattering improves the throughput efficiency by a factor of approximately 4 in comparison to a triple-stage spectrograph. The instrument has a spatial resolution of approximately 3 μm × 9 μm in the lateral (X–Y) plane, and 10 μm or less in the axial (Z) plane. UV resonance Raman spectra of nucleic acids are selectively excited from spatially resolved areas of a single paramecium by using low continuous-wave (cw) excitation powers and short accumulation times to minimize sample damage. High signal-to-noise Raman spectra are excited from spatially resolved areas of chemical-vapor-deposited (CVD) diamond films. We demonstrate, for the first time, the ability to probe the spatial distribution of the nondiamond carbon impurities in CVD diamond films. The amorphous carbon band at ∼ 1553 cm−1 is resolved from the normally broad ∼ 1600-cm−1 nondiamond carbon band.
Spectrochemical Analysis of Liquids Using Laser-Induced Plasma Emissions: Effects of Laser Wavelength
Authors: Ho W. F. , Ng C. W. , Cheung N. H.
Published: October 2003

The plasma plume emissions produced by pulsed (∼ 10 ns) laser ablation of liquid jets were monitored for spectrochemical analysis. Laser wavelengths at 532 and 193 nm were used, and sodium was the test analyte. As expected, the 532-nm laser pulse produced very intense plasma continuum emissions that masked the sodium signal for the first hundred nanoseconds, especially near the bright core of the vapor plume. Neither time-gating nor spatial masking could significantly improve the single-shot signal-to-noise ratio, since the transient nature of the emissions placed stringent demands on timing precision while the small size of the plume required accurate mask positioning—both antithetical to the inherent instability of jet ablation. In sharp contrast, the 193-nm laser pulse produced relatively dim plasma flash but intense sodium emissions, rendering it ideal for analytical applications.
Correcting Fluctuating Baselines and Spectral Overlap with Genetic Regression
Authors: Paradkar Rajesh P. , Williams Ronald R.
Published: October 2003

The application of a new algorithm, known as genetic regression (GR), to calibration problems with spectra containing complex fluctuating baselines is illustrated with the use of synthetic data. The ability of the algorithm to automatically compensate for the presence of linear and polynomial (quadratic and cubic) baselines in the presence of complex spectral overlap is investigated along with the effect of noise. GR is unique in that it provides an effective wavelength optimization technique by sorting through the spectr al data and selecting and appropriately combining wavelengths that compensate for structured baseline and spectral overlap. The results obtained with GR are compared with those obtained with background-corrected linear regression. GR is shown to give much better results and, in constrast to traditional background correction, is much faster and can compensate for the presence of both structured baseline and complex spectral overlap simultaneously. The results of a noise study show that the method works at low signal-to-noise ratio (SNR) and that the error in the final result is a function of the noise.
Simplified Calibration of Instrument Response Function for Raman Spectrometers Based on Luminescent Intensity Standards
Authors: Ray Kenneth G. , McCreery Richard L.
Published: October 2003

Published Raman spectra are rarely corrected for variations in spectrometer sensitivity across the Raman spectrum, which leads to often severe distortion of relative peak intensities that impede calibration transfer and library searching. A method was developed that uses the known luminescence of standards which fluoresce in response to laser irradiation. Since the standards are observed with the same sampling geometry as the Raman sample of interest, their spectra are subject to the same instrumental response function. After one-time calibration of the standards' fluorescence output against a known tungsten source, the unknown Raman spectrum may be corrected for instrumental response by a simple formula. In practice, the user need only run the standard under the same conditions as the Raman sample, then apply a short GRAMS algorithm. The approach is demonstrated for coumarin 540a and Kopp 2412 glass standards, with 514.5- and 785-nm laser light, respectively. Once the corrected spectrum is in hand, the absolute Raman cross section of a given Raman feature may be determined by comparison to known scatterers such as benzene.
Electron Paramagnetic Resonance Studies of Impurity Defects in PbTiO3
Authors: Keeble D. J. , Poindexter E. H. , Gerardi G. J.
Published: October 2003

Electron paramagnetic resonance studies of metal ion impurities in the perovskite titan ate PbTiO3 are presented. Results for Pt+3, Mn+4, and Cu+2 are given, and near-neighbor superhyper fine structure (shfs) splittings for the first Pb shell are reported for these ions at low temperature. The relation between the shfs and the local structure of the ion is discussed.
Using Raman Microscopy to Detect Leaks in Micromechanical Silicon Structures
Authors: Weber W. H. , Zanini-Fisher M. , Pelletier M. J.
Published: October 2003

We demonstrate the use of Raman microscopy for leak detection in hermetically sealed micromachined accelerometers. Leaks were indicated by the presence of a foreign gas, in this case oxygen, in the 70-μm-deep cavity enclosing the accelerometer between a silicon cap and a Pyrex® window. Confocal, nondiffraction-limited operation of the Raman microscope utilized the available pathlength in the sample while still rejecting most of the fluorescence from the Pyrex®. Raman peak intensities were accurately determined in the presence of noise by fitting the spectra to a function that modeled the unresolved Q-branch line shapes of oxygen and nitrogen.
Determination of Solubility Limits of Photocured PDLC Systems Using Infrared Microspectroscopy
Authors: Challa Sudarsana R. , Wang Shi-Qing , Koenig Jack L.
Published: October 2003

Infrared microspectroscopy is used to determine the solubility limits of a UV-curable polymer-dispersed liquid crystal (PDLC) system comprised of a low-molecular-weight liquid crystal (E7) and a photocurable monomer (NOA65). The LC is allowed to diffuse into the monomer by the contact method, and then the sample is subjected to curing. The morphology of the system after polymerizaton exhibits several distinct spatial regions, and the associated concentration gradients are measured. At an irradiation temperature of 30 °C, the concentration of LC in the matrix is found to be 27 ± 3%, and at a temperature of 100 °C, it is 65 ± 3%.
New Simple Method to Analyze Mildly Gaussian-Convolved Lorentzian Lines with the Aid of DISPA Data
Authors: Jiménez-Domínguez H. , CRuz-Jiménez S. , Cabral-Prieto A.
Published: October 2003

A new and simple method, not based on numerical fitting, to analyze mildly Gaussian-convolved Lorentzian isolated nonoverlapped lines in any spectroscopy, with the aid of DISPA (DISPersion vs. Absorption) data, is presented. The method is based on a model of the dispersion line which is obtained by taking the Hilbert transform of a previously published approximate expression for the absorption Voigt profile. The resulting DISPA pair is valid in the interval α, where α is a parameter that measures the relative Lorentzian (ΓL) and Gaussian (ΓG) full width at half-maximum (FWHM) contributions to the Voigt profile. As an example of an application of the method, a deconvolution of the potassium–ammonium solution electron paramagnetic resonance (EPR) line is performed. This deconvolution produces the Lorentzian and Gaussian contributions to the line. The deconvolution operation is done after obtaining a list of DISPA values for this line. The resulting values of the Lorentzian and Gaussian FWHMs are then compared with those obtained after deconvolving the line by fitting the spectral data with both the exact and approximate expressions for the Voigt profile. The method may be used in any spectroscopy in which the spectral lines are not overlapped and can be represented by Voigtians with a small Gaussian component and with a very low degree of asymmetry.
Effect of Temperature Variation on FT-IR Spectrometer Stability
Authors: MacBride D. M. , Malone C. G. , Hebb J. P. , Cravalho E. G.
Published: October 2003

The effect of temperature variation on Fourier transform infrared (FT-IR) spectrometer response stability is investigated for wavenumbers from 10,000 to 100 cm−1 with the use of a temperature measurement and data acquisition system on the spectrometer optical bench. Spectrometer response instability is correlated with local temperature variation for two FT-IR spectrometer systems, with the use of various infrared source, beamsplitter, and detector combinations. The data obtained show that detector responsivity variation and beamsplitter misalignment associated with thermal instability of the spectrometer optical bench are responsible for the observed response instability. Response variation of up to 4% per °C temperature variation is observed. Variations of the laboratory environment and spectrometer purge gas supply temperatures are shown to affect spectrometer thermal stability directly.
Photoacoustic Depth-Resolved Analysis of Tissue Models
Authors: Beenen A. , Spanner G. , Niessner R.
Published: October 2003

Pulsed photoacoustic laser spectroscopy was used for depth-resolved analysis of artificial tissue models. The technique was applied to investigate the spatial resolution capabilities of a fiber-optical-coupled photoacoustic sensor head. The time-resolved measurements confirmed the theoretical predictions of a depth resolution of 0.1 mm. In an adapted skin model, a strongly absorbing target could be detected up to a layer depth of 14 mm. At a layer depth of 5 mm, a lateral resolution of 3.5 mm was achieved. Because of the depth-resolving capability, this method is well suited as a complementary approach for two-dimensional imaging techniques.
Excitation Temperature in High-Power Nitrogen Microwave-Induced Plasma at Atmospheric Pressure
Authors: Ogura Kenichi , Yamada Hirofumi , Sato Yoshitaka , Okamoto Yukio
Published: October 2003

Excitation temperature, rotational temperature, and electron density were obtained for a high-power (1-kW) microwave-induced nitrogen plasma (N2 MIP) at atmospheric pressure generated by an Okamoto cavity. With 1 kW input microwave power, an excitation temperature of 5500 K, a rotational temperature of 5000 K, and an electron density in the 1013 range were measured. Excitation and rotational temperatures were much closer than is the case with the commonly used argon inductively coupled plasma, suggesting that this N2 MIP is closer to local thermodynamic equilibrium (thermal).