bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of Parasites in Cod Fillets by Using SIMCA Classification in Multispectral Images in the Visible and NIR Region
Authors: Wold Jens Petter , Westad Frank , Heia Karsten
Published: October 2003

The presence of parasitic nematodes in fillets of commercially important fish species has been a serious quality problem for the fishing industry for several decades. Various approaches have been tried to develop an efficient method to detect the parasites, but so far the only reasonable solution is manual inspection and trimming of each fish fillet on a candling table. In this study we have investigated how multispectral imaging in combination with SIMCA classification can be used for automatic detection of parasites. The results indicate that the spectral characteristics of nematodes differ sufficiently from those of fish flesh to allow one to obtain fairly good classifications. The method is able to detect parasites at depths down to about 6 mm into the fish muscle. The method shows promising results, but further studies are required to verify feasibility for the fish industry.
Monitoring Dielectric Thin-Film Production on Product Wafers Using Infrared Emission Spectroscopy
Authors: Niemczyk Thomas M. , Zhang Songbiao , Haaland David M.
Published: October 2003

Monitoring of dielectric thin-film production in the microelectronics industry is generally accomplished by depositing a representative film on a monitor wafer and determining the film properties off line. One of the most important dielectric thin films in the manufacture of integrated circuits is borophosphosilicate glass (BPSG). The critical properties of BPSG thin films are the boron content, phosphorus content, and film thickness. We have completed an experimental study that demonstrates that infrared emission spectroscopy coupled with multivariate analysis can be used to simultaneously determine these properties directly from the spectra of product wafers, thus eliminating the need for producing monitor wafers. In addition, infrared emission data can be used to simultaneously determine the film temperature, which is an important film production parameter. The infrared data required to make these determinations can be collected on a time scale that is much faster than the film deposition time, hence infrared emission is an ideal candidate for an in situ process monitor for dielectric thin-film production.
Novel Route to Faster Fourier Transform Infrared Spectroscopic Imaging
Authors: Bhargava Rohit , Schaeberle Michael D. , Fernandez Daniel C. , Levin Ira W.
Published: October 2003

Fourier transform infrared (FT-IR) spectroscopic imaging microscopy couples a focal plane array (FPA) detector, integrated within an infrared microscope assembly, to an interferometer for attaining a multiplex/multichannel signal detection advantage. While this configuration should enable the acquisition of spatially resolved spectra over the entire field of view of a sample in the time that it takes a conventional FT-IR spectrometer to record a single spectrum, data acquisition in an imaging modality is an intrinsically slower process. We present a novel collection technique for step-scan, micro-imaging spectrometers that both allows large numbers of samples to be imaged rapidly and provides higher signal-to-noise ratios (SNRs) for given experimental time intervals. For example, data may be collected in as little as one minute, while SNRs greater than 800 are achieved for data acquired in less than 10 min. Imaging data acquired in the proposed, more rapid approach exhibit no loss in fidelity compared to data recorded by the conventional imaging techniques.
Detection Limit and Decision Thresholds in Spectrometry
Authors: Méray L. , Demény O.
Published: October 2003

A critical approach to the conventional definition of the detection limit and the decision threshold is introduced. Equations describing the probability of having more (or less) sample present than a given lower (or upper) limit are introduced, with the use of two different methods to calculate the value of net counts. The calculations are based on probability theory. Examples from low-count experiments and simulations are given.
Raman and Infrared Microspectroscopic Mapping of Plasma-Treated and Grafted Polymer Surfaces
Authors: Keen I. , Rintoul L. , Fredericks P. M.
Published: October 2003

The grafting of polystyrene (PS) onto a predominantly polypropylene (PP) substrate has been followed by Raman and infrared microspectroscopic mapping. For exactly the same 50 μm × 50 μm section of polymer surface, Raman spectra were obtained at 1 μm intervals for the substrate, the surface after plasma treatment, and the surface after PS grafting. Maps of the substrate were constructed, indicating the crystallinity variation across the surface and also the distribution of the minor component ethylene-propylene rubber (EPR). After plasma treatment, the crystallinity was found to decrease slightly. Infrared microspectroscopic maps of a larger plasma-treated surface were also obtained with the technique of attenuated total reflection. The spatial resolution of these maps was 50 μm, and they showed the distribution of the hydroxy groups introduced onto the surface by the plasma treatment. PS grafting was found to be heterogeneous. Increased concentrations of grafted PS showed some correlation with positions on the surface which had higher EPR after plasma treatment.
High Sensitivity Spectrograph for Use in Fluorescence Microscopy
Authors: Frederix P. L. T. M. , Asselbergs M. A. H. , Van Sark W. G. J. H. M. , Van Den Heuvel D. J. , Hamelink W. , De Beer E. L. , Gerritsen H. C.
Published: October 2003

In this paper a versatile, high sensitivity spectrograph is presented for use in fluorescence microscopy. The high sensitivity is achieved by using a prism for the dispersion in combination with a state-of-the-art back illuminated charge-coupled device (CCD) camera. The spectrograph, including the CCD camera, has a detection efficiency of 0.77 ± 0.05 at 633 nm. Full emission spectra with a 1–5 nm spectral resolution can be recorded at a maximum rate of 800 spectra per second. Two applications are shown, in which the spectrograph is fiber-coupled to a commercial confocal laser scanning microscope. In the first example, Förster resonance energy transfer imaging experiments were carried out on double-labeled actin filaments in the in vitro motility assay. A 160 × 160 point image was recorded in 1.5 min at 3 ms dwell time per image point. In the second application, a time-resolved study of single quantum dots is presented at 5.2 ms time resolution.
Highly Multiplexed Optically Sectioned Spectroscopic Imaging in a Programmable Array Microscope
Authors: Hanley Quentin S. , Jovin Thomas M.
Published: October 2003

We report the construction of a spectroscopic programmable array microscope capable of optical sectioning using Hadamard transform methods. Previously described Hadamard transform imaging consisted of first-order systems in which the mask was used for either illumination or detection. In this paper, a second-order Hadamard transform system is described in which a single one-dimensional mask serves for both illumination and detection. The system verifies earlier predictions that the optical spreading function along the transform axis can be inferred from the echoes arising in second-order systems using sequence lengths of 2 n-1. With a one-dimensional Hadamard mask, the system has an axial resolution of 1.3 μm and may be used with or without the subtraction of an appropriately scaled wide field image depending on the degree of sectioning required. The system was tested using thin films, fluorescent beads, and a fixed biological specimen.
Influence of the Isotopic Composition of Standards on the Accuracy of Atomic Spectrometry for the Determination of Lithium
Authors: Goode Scott R.
Published: October 2003

Analysis by atomic spectroscopy depends on the comparison of the signal generated by the sample to the signal generated by a standard. If the isotopic distribution of the analyte element in the sample differs substantially from the isotopic distribution in the standards, then an error will result. The magnitude of the error depends on the differences in abundances and on the wavelength differences between the analysis lines of the isotopes. If the analysis is performed by atomic absorption spectrometry, the error is also influenced by the isotopic distribution in the hollow cathode lamp. In the determination of lithium by emission the relative errors can reach 6% for an enriched (40 atom% 6Li) sample. In atomic absorption, the relative errors in the lithium concentrations can reach 50% for an enriched sample.
Water Content in Micelles of Poly(ethylene Oxide)—Poly(Propylene Oxide)—Poly(ethylene Oxide) Triblock Copolymers in Aqueous Solutions as Studied by Fluorescence Spectroscopy
Authors: Nakashima Kenichi , Takeuchi Keisuke
Published: October 2003

Fluorescence spectroscopy has been applied in the investigation of water content in micelles of polyethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers at 20 and 50 °C. The triblock copolymers examined consist of Pluronic F68® (F68) and Pluronic L64® (L64), which are known to form micelles with cores of PPO and shells of PEO in aqueous solutions. 2- p-Toluidinylnaphthalene-6-sulfonic acid (TNS) is used as a fluorescence probe. Several fluorescence parameters of TNS are employed as tools to evaluate the water content in the micelles: (1) the wavelength at maximal intensity, which strongly depends on the polarity and viscosity of the surrounding media; and (2) the degree of polarization (P) and lifetime, which give the microviscosity of the media through the Perrin-Weber equation. Aqueous solutions of PEO of various compositions are used as standard solutions. It is found that the water content in F68 and L64 micelles ranges from 10 to 70 wt %, depending on the size of the PEO block, concentration of the polymer, and temperature. The usefulness of fluorescence spectroscopy in the studies of block copolymer micelles is demonstrated along with some comments on the interpretation of P of the TNS probe.
Pharmacologic Application of Fourier Transform Infrared Spectroscopy: The in vivo Toxic Effect of Carrageenan
Authors: Perromat Annie , Melin Anne-Marie , Déléris Gerard
Published: October 2003

Microsomal fractions from rat brain, testes, and liver were examined by means of Fourier transform infrared spectroscopy to study the in vivo toxic effect of carrageenan administered by intraperitoneal injection. Comparison between spectra of control and treated samples clearly demonstrated important cellular damages induced by carrageenan. Lipid content was significantly enhanced in the testes and brain. The length of the acyl chains largely increased, and cholesterol ester accumulation occurred as a consequence of lipid peroxidation, particularly in the brain. Absorption intensity in the amide I and II regions was increased in the brain and testes. Conformational structure of membrane proteins was changed as shown by the large decrease in liver β-sheet structures. The phospholipid level was more significantly enhanced in the brain than in the testes. We observed in liver both an important loss in glucidic structures and a noticeable glycogen depletion. Thus, Fourier transform infrared spectroscopy appears to be a useful tool to rapidly monitor the chemical alterations induced by carrageenan on different organs. Moreover, a correlation between the spectroscopic method and the biochemical data was discussed. Further experiments should be conducted to investigate the spectral features characteristic of the various tissue types within each organ and to explore new markers for oxidation and/or inflammation.
Reflection Absorption Infrared Spectra of Thin Solid Films. Molecular Orientation and Film Structure
Authors: Antunes P. A. , Constantino C. J. L. , Aroca R. , Duff J.
Published: October 2003

The calculated and observed vibrational spectra of a new series of perylene tetracarboxylic derivatives (PTCDs) with different alkyl lateral chain lengths (5, 10, 15, and 20 C) are reported. With the use of characteristic vibrational modes, the question about the degree of molecular organization and packing in these PTCD evaporated films has been resolved by using transmission and reflection-absorption infrared spectroscopy (RAIRS) techniques. From vibrational analysis, it was extracted that the molecules are preferentially oriented with the PTCD moiety head on the surface substrate. The molecular organization detected (by using RAIRS) in the evaporated films is not changed when the films are exposed to different solvents, such as water, methanol, and propanol, or when they are annealed up to 155 °C under normal atmospheric conditions or in vacuum. Evidence of molecular packing in the evaporated films is also provided by the observation of strong excimer emission.
Optical Contact in ATR/FT-IR Spectroscopy
Authors: Ekgasit Sanong , Padermshoke Adchara
Published: October 2003

Optical contact between an internal reflection element (IRE) and a sample is crucial for obtaining a good spectrum in an attenuated total reflection (ATR) experiment. When an air gap is present between the IRE and the sample, the spectrum severely deteriorates. Two techniques for determining the goodness of contact are proposed—first, by making a comparison between polarized ATR spectra and, second, by making a comparison between ATR and transmission spectra. When the optical contact is achieved, the normalized p-polarized ATR spectrum is exactly the same as the normalized s-polarized ATR spectrum. Moreover, the ratio between the normalized absorbance measured in the ATR mode and the normalized absorbance measured in the transmission mode equals the ratio between the frequency being considered and the normalization frequency. Theoretical and experimental investigations have been performed in order to verify the proposed techniques.
Phase References and Cell Effects in Photoacoustic Spectroscopy
Authors: Jones Roger W. , McClelland John F.
Published: October 2003

In Fourier transform infrared (FT-IR) photoacoustic spectroscopy, advanced scanning and data-handling techniques have placed increasing emphasis on the phase of the photoacoustic signal. Unfortunately, there is no agreement on the best material to use as a phase reference. We have examined the frequency dependence of the signal from several candidate phase references and found that cell effects dominate the absolute phases and magnitudes observed. The absolute phase is exceptionally fast at low frequencies and exceptionally slow at high frequencies because of the cell effects. Accordingly, details such as sample position must be scrupulously controlled to achieve accurate, reproducible results. Because of the cell effects, no candidate material behaves like an ideal phase reference. If relative phases are used, however, glassy carbon comes closest to the ideal, differing from theory by no more than 8° at any frequency examined.
Direct Solids Atomic Emission Spectrometric Analysis of Metal Samples by “Laser-Induced Argon Spark Ablation” Coupled to ICP-OES
Authors: Kehden A. , Flock J. , Vogel W. , Broekaert J. A. C.
Published: October 2003

A new type of laser ablation system (laser-induced argon spark atomizer) combined with inductively coupled plasma optical emission spectrometry (ICP-OES) was used for the direct analysis of compact metallic samples. The material is ablated with the aid of a Nd:YAG laser (λ = 1064 nm, 300 mJ/pulse, ν = 4–20 Hz) and entered with a carrier-gas into a commercial ICP-OES system (Plasma 2000, Perkin–Elmer) with two monochromators. The influence of the laser parameters (pulse frequency and power) on the ablation rate and the particle size of the ablated material were investigated, and they were found to range from 1.0 to 16.7 μg/s and below 100 nm, respectively. In the case of brass samples, selective evaporation of the matrix elements Cu and Zn was found to occur. Laser parameters such as frequency, power, and ablation time were found not to influence the selective evaporation of Cu and Zn significantly. The detection limits for Ni, Cr, Mo, Mn, and Si in low-alloyed steel; Fe, Ni, Sn, and Pb in brass; and Fe, Cu, and Si in aluminum were found to be at the 20–100 μg/g level, independent of the sample matrix. The long-term stability of the emission signal was found to be better than 5% for ablation times of up to 10 min, and relative standard deviations usually are between 1 and 5%. For Mo, Mn, Si, Ni, and Cr in the BAS SS 435 sample, good agreement of the analytical results at the 0.01–0.5% level with certified values could be obtained when calibrating with other BAS standard reference samples.
Effect of Pulse Delay Time on a Pre-Ablation Dual-Pulse LIBS Plasma
Authors: Stratis Dimitra N. , Eland Kristine L. , Angel S. Michael
Published: October 2003

In this paper, we investigate the effect of dual-pulse timing on material ablation, plasma temperature, and plasma size for pre-ablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS). Although the plasma temperature increases for dual-pulse excitation, the signal enhancement is most easily attributed to increased sample ablation. Plasma images show that the magnitude of the enhancement can be affected by the collection optic and by the collection geometry. Enhancements calculated using the total integrated intensity of the plasma are comparable to those measured using fiber-optic collection.
Detection of Anionic Nutrients by SERS of Cationic-Coated Silver Substrates. Effect of Chloride Ion
Authors: Mosier-Boss P. A. , Lieberman S. H.
Published: October 2003

Earlier it was demonstrated that surface-enhanced Raman spectroscopy (SERS) of cationic-coated silver substrates could successfully detect nitrate and sulfate in the parts-per-billion to parts-permillion concentration range. However, these cationic coatings also interact with chloride ion. In this paper, the magnitude of the chloride ion interference is examined. To eliminate the interference, we explore the use of selective ionophores and solid-phase extraction (SPE).
Effects of Freeze-Thaw and Photobleaching on the Ultraviolet Resonance Raman Spectra of Human Colon Biopsies
Authors: Boustany Nada N. , Crawford James M. , Manoharan Ramasamy , Dasari Ramachandra R. , Feld Michael S.
Published: October 2003

We studied the effects of sample freezing and thawing, laser fluence, temperature, and oxygen on the ultraviolet resonance Raman (UVRR) spectra of human colon biopsies at 251 nm excitation. We show that the total adenylate content of the tissue decreases as a result of freezing and subsequent thawing to room temperature. We also show that photobleaching is the result of oxidative as well as thermal damage. Photobleaching consisted of a decrease in the intensity of the purine spectral bands and broadening and intensity increase of the aromatic amino acid bands. Both bio- and photodegradation of the tissue can be minimized by keeping the biopsy samples refrigerated during testing and the laser fluence under 0.2 mJ/μm2. Unlike amino acid photobleaching, purine photobleaching was also greatly reduced by placing the samples in an argon atmosphere. Sample storage could be achieved by refrigerating the fresh specimens and testing them within 30 h of surgical resection, without freezing. Alternatively, the fresh specimens could be snap-frozen in liquid nitrogen, then thawed and tested for up to 30 min. Altogether, these studies can be utilized to guide future experimental design and data interpretation during ultraviolet spectroscopy of biological tissues.
Stripping of Cosmic Spike Spectral Artifacts Using a New Upper-Bound Spectrum Algorithm
Authors: Zhang Dongmao , Jallad Karim N. , Ben-Amotz Dor
Published: October 2003

A new upper-bound spectrum (UBS) method for removal of cosmic spike artifacts from spectra or images collected using a charge-coupled device (CCD) detector is proposed. This algorithm, which is shown to outperform previous methods, relies on an upper-bound spectrum, derived from scaled copies of consecutively collected spectra, which serves as a threshold for the detection of suspected cosmic spikes. Detected spikes are removed by replacement with the corresponding points in other spectra. Thus, unlike other commonly used methods, the UBS algorithm requires no smoothing or noise filtering and more reliably removes cosmic spikes of all magnitudes while introducing far less (if any) spectral distortion. The UBS method is tested using both synthetic and experimental (gypsum and gypsum/hematite mixture) spectra containing variable background (fluorescence), noise, and cosmic spike interference. The UBS method may in rare instances mistakenly identify spectral noise or photo-induced changes in band intensity (or shape) as cosmic spikes. However, as demonstrated through the use of both synthetic and experimental examples, such misidentifications produce little or no spectral distortion or artifacts in the resulting cosmic-spike-free output spectra.
Outlier Detection in the Ethylene Content Determination in Propylene Copolymer by Near-Infrared Spectroscopy and Multivariate Calibration
Authors: Macho S. , Sales F. , Callao M. P. , Larrechi M. S. , Rius F. X.
Published: October 2003

In this study, we employed multivariate control techniques to detect outliers in the determination of ethylene in impact polypropylene samples by near-infrared (NIR) spectroscopy and multivariate calibration partial least-squares (PLS). We also applied an algorithm which identifies those spectral variables responsible for the outlier behavior and that can indicate the source of this behavior. The outliers in the prediction step may be due to three possible situations: errors associated with the prediction of analyte concentrations in samples that have the same characteristics as the calibration set, but that are beyond the concentration range; changes in the matrix composition; and instrumental errors. We show that the proposed techniques make it possible to detect whether or not an analyte belongs to the reference set. In addition, we apply an algorithm that identifies the variables that cause outlier behavior and assigns them to a class.
Enclosed Inductively Coupled Plasma: Spatially Resolved Profiles of Rotational Temperatures and Analyte Atom Distribution
Authors: Breer C. , Engel U. , Klostermeier A. , Buscher W. , Broekaert J. A. C. , Cammann K.
Published: October 2003

In order to investigate evaporation and desolvation capacities of the enclosed inductively coupled plasma discharge, rotational temperatures (which are commonly considered a good approximation of the heavy particle temperature or gas temperature) were determined as a function of their spatial distribution and their dependence on physical parameters such as gas flows (80–740 mL/min), moisture load, etc. The procedure utilizes the fine structure of the (A2Σ+ → X2Πi) OH band having its band head at 306.4 nm. The rotational temperatures were obtained from the slopes of their Boltzmann plots. Spatial resolution and simultaneous line detection was possible by using a charge-coupled device (CCD) camera in the focal plane of the removed exit slit of a Czerny–Turner monochromator. An interactive data language (IDL) program was developed to calculate the temperature distribution from the received CCD images. Results of the measurement show that the rotational temperatures are between 3750 and 4350 K. They further show the M-shaped spatial profile of analyte intensities and temperature. In the examined gas flow range (80–740 mL/min) the dependence on absolute gas flows and moisture load (5 mg/L) is negligible.
Cyclodextrin-Induced Room-Temperature Phosphorescence of 1-Bromo-2-naphthol upon Formation of Ternary Complexes
Authors: Santos Marina , Escandar Graciela M.
Published: October 2003

The inclusion constant for the 1:1 binary complex between 1-bromo-2-naphthol and β-cyclodextrin in aqueous solution was determined by a spectrofluorimetric method. On the basis of MO calculations, a possible structure of this complex was proposed and compared with those formed by two related naphthol derivatives. After the addition of different alcohols (linear, branched, and cyclic) to the 1-bromo-2-naphthol–β-cyclodextrin solution, a significant enhancement of the room-temperature phosphorescence (RTP) was observed. Both the formation constants and stoichiometries of the formed ternary complexes were determined from RTP data with the use of the computational program EPSILON. It was verified that RTP was also induced by adding different apolar liquids (cyclohexane and 1,3-dibromopropane) as the third component instead of alcohols. Of all the examined compounds, cyclohexanol produced both the largest RTP signal and the more stable ternary complex. The RTP calibration graph for 1-bromo-2-naphthol in the presence of both β-cyclodextrin and cyclohexanol was linear for the range of concentrations between 0.6 and 4.0 μg mL−1 with a limit of detection of 0.2 μg mL−1, with a relative standard deviation ( n = 4) of 4%, for 2.2 μg mL−1.
Quantification of Large Scale Micro-X-Ray Fluorescence Elemental Images
Authors: Worley Christopher G. , Havrilla George J. , Dunn Paul S.
Published: October 2003

Niobium is commonly alloyed with uranium to prevent surface oxidation, and determining how the niobium concentration is distributed throughout a sample is useful in explaining observed material properties. The niobium concentration distribution was determined across the surface of depleted uranium samples using micro-X-ray fluorescence (MXRF). To date, MXRF has been employed primarily as a qualitative tool for determining relative differences in elemental concentrations across a sample surface. Here, a process was developed to convert qualitative MXRF niobium distribution images from depleted uranium samples into images displaying concentration values. Thus, MXRF was utilized to determine elemental concentrations across a surface in a manner similar to that of the established method of electron microprobe X-ray analysis (EMPA). However, MXRF can provide such information from relatively large sample areas many cm2 in size that are too large to examine by the higher spatial resolution technique of EMPA. Although the sample surfaces were polished to the same degree as the standards, little or no sample preparation should be necessary for sample systems where a high energy analyte XRF line can be used for imaging.
Pareto Optimal Multivariate Calibration for Spectroscopic Data
Authors: Kalivas John H. , Green Robert L.
Published: October 2003

Multivariate calibration of spectral data is considered with an emphasis on prediction. An abundance of methods are available to develop such calibration models. Using a harmonious approach with target vector optimization, the best calibration models are identified relative to the criteria used. Criteria utilized to determine the adequacy of models are minimization of the root mean square error of calibration (RMSEC) and the norm of the regression vector. Because of the simplicity of the optimization response surfaces, the method of simplex was found to function much faster than generalized simulated annealing. Using a near infrared spectral example to demonstrate concepts, a family of models are established to be good, i.e., Pareto optimal models. For the data set investigated, it is found that the Pareto optimal models are essentially the same as models obtained by ridge regression and generalized ridge regression and are more harmonious than models obtained by principal component regression (PCR), partial least-squares (PLS), continuum regression, and cyclic subspace regression as the Pareto optimal models have smaller regression vector norms, RMSEC, and root mean square error of validation (RMSEV) values. The PLS models are found to be Pareto optimal relative to the PCR models. The paper presents an explanation of when the RR model will not be acceptable.
Electrospray-Ionization Time-of-Flight Mass Spectrometry: pH-Dependence of Phosphotungstate Species
Authors: Easterly C. Elliott , Hercules David M. , Houalla Marwan
Published: October 2003

Electrospray-ionization (ESI) time-of-flight mass spectrometry has been used to investigate the pH-dependent behavior of phosphotungstates in solution from pH = 2.7 to 8.0. Mass spectra are reported for the first time for H3PW11O394–, H4PW11O393–, and H5PW11O392–. The pH dependence of phosphotungstate species as measured by electrospray is compared with that measured by 31P NMR. The pH ranges of species are similar (±1 pH unit) when measured by these two methods. Protonation and solvation of phosphotungstate species measured by ESI differ from those observed by 31P NMR. However, the core phosphotungstate species are measured correctly by ESI.
Use of near Edge X-Ray Absorption Fine Structure Spectromicroscopy to Characterize Multicomponent Polymeric Systems
Authors: Smith A. P. , Urquhart S. G. , Winesett D. A. , Mitchell G. , Ade H.
Published: October 2003

The merits of a polymer characterization technique, near edge X-ray absorption fine structure (NEXAFS) spectromicroscopy, are demonstrated through the characterization of a multilayer polymer film with partially unknown chemical composition. The combination of chemical speciation through NEXAFS spectroscopy with the high spatial resolution available in X-ray microscopy allows the characterization of polymeric materials not possible with conventional techniques. Analysis of a multilayer with layers as thin as 4 μm has yielded results that differ from those previously obtained by infrared microscopy. Layers below the spatial resolution limit of infrared microscopy were characterized.
Determination of Hemoglobin Oxygen Saturation from Turbid Media Using Reflectance Spectroscopy with Small Source-Detector Separations
Authors: Johns Maureen , Giller Cole A. , Liu Hanli
Published: October 2003

In this study, we present an empirically modified diffusion model determining hemoglobin oxygen saturation from turbid media using steady-state, broadband (500–600 nm) reflectance with source-detector separations of a few hundred micrometers. Development of this model was conducted using Monte Carlo simulations, a gold standard modeling technique for predicting the behavior of light propagation through turbid media. Hemoglobin oxygen saturation levels of 0 and 100% at different blood concentrations were studied. Nonlinear curve fitting was used to extract the hemoglobin oxygen saturation values from the reflectance spectra, producing errors of 5% between the simulated curves and the model for both saturation cases. Further validation was performed using liquid-tissue phantoms containing intralipid and blood. Curve fitting between the in vitro data and the model produced errors of less than 2%. This validated model was then used to extract saturation values from in vivo reflectance spectra of the human index finger and human brain tissues. This empirically modified diffusion model provides the possibility of extracting local hemoglobin oxygen saturation from blood-perfused turbid media using reflectance data measured with a small source-detector separation probe.
Silver Coated Porous Alumina as a New Substrate for Surface-Enhanced Raman Scattering
Authors: Walsh Richard J. , Chumanov George
Published: October 2003

Porous alumina filters were coated by vacuum deposition with silver metal and used as substrates for surface-enhanced Raman scattering (SERS). These were studied by UV-Vis absorption spectroscopy and scanning electron microscopy. The substrates exhibit reproducible Raman enhancement for different molecules tested in this study. The mass thickness of the silver was optimized for maximal SERS signal using bipyridine as a model compound. Plasma treatment of the substrates prior to SERS measurements was identified as a crucial factor for a low background and high signal-to-noise Raman spectra. The effect of different plasma treatment conditions on the SERS signal as well as on UV-Vis absorption spectra of the substrates was investigated. After the silver deposition, the porous alumina retained its filtering abilities and could be used for preconcentrating dilute analytes on the substrate surface for SERS measurements. Corresponding tests were performed using benzotriazole and bipyridine solutions. These substrates demonstrate a potential for large-scale applications in different analytical measurements.
Analysis of Binary Solvent Diffusion into Cross-Linked Poly (Butadiene) Using Fast Scan Fourier Transform Infrared Imaging Spectroscopy
Authors: Shin Eun-Mi , Ribar Travis , Koenig Jack L. , Wright Norman
Published: October 2003

The diffusion of a binary solvent mixture into cross-linked poly (butadiene) (PBD) was observed using fast scan FT-IR imaging spectroscopy. Spatial correlation of solvent ingress and polymer swelling was established with a temporal resolution of 20 s. Binary solvent mixtures included a good-good solvent pair of benzene-cyclohexane (50/50 wt%) and a good-poor solvent pair of toluene-methanol (50/50 wt%). A set of FT-IR images was collected over time, from which the profiles of solvent ingress and polymer swelling were extracted. The Boltzmann transformation, which explains diffusion phenomena with respect to both time and position simultaneously, was used to obtain a curve, which indicates that benzene and cyclohexane diffuse similarly, but toluene and methanol have different diffusion behavior. The good-good solvent pair (benzene-cyclohexane mixture) ingressed into polymer together, while the good-poor solvent pair (toluene-methanol mixture) showed independent ingression behavior. The good solvent (toluene) aggressively diffused into polymer while the poor solvent (methanol) remained in solution.
Reduction of Multiexponential Background in Fluorescence with Phase-Sensitive Detection
Authors: Crowell Edward , Geng Lei
Published: October 2003

Fluorescence detection in a complex matrix often requires the reduction of background signals. Fluorescence lifetime-based methods have been an effective approach to suppressing the undesired background, especially when substantial spectral overlap precludes optical filtering. We introduce a methodology of suppressing a fluorescence background that contains multiple species for the quantification of a single fluorescent analyte. The method is based on the recognition that the multiexponential decay of the fluorescence background can be described by a single phase angle when the sample is excited by a sinusoidally modulated beam. The reduction of the total background is accomplished by setting the detector 90 degrees out of phase from the total background fluorescence. The background reduction is demonstrated with ternary samples containing pyrene (τ = 18.2 ns), anthracene (τ = 4.5 ns), and 1,4-bis(5-phenyl-2-oxazolyl)benzene (POPOP, τ = 1.35 ns). The component with the shortest lifetime (POPOP) is successfully analyzed after the background from longer-lived components (pyrene and anthracene) is reduced. The phase-sensitive detection enables simultaneous suppression of background fluorescence with lifetimes longer and shorter than the analyte, as demonstrated by the quantification of anthracene in a background composed of pyrene and POPOP. These samples present situations that cannot be treated by traditional methods of fluorescence background reduction. An effective fluorescence spectrum of the analyte is collected after the multiexponential background is eliminated. The method is especially useful when the total concentration of the background displays significant fluctuations. When the variations in the background fluorescence intensity are comparable or exceed the analyte fluorescence, the analyte cannot be quantified with steady state fluorescence measurements. The phase-sensitive method, however, effectively quantifies the analyte with excellent linearity in calibration.
Theory and Application of Gain Ranging to Fourier Transform Infrared Spectroscopic Imaging
Authors: Bhargava Rohit , Fernandez Daniel C. , Schaeberle Michael D. , Levin Ira W.
Published: October 2003

Gain ranging is incorporated into the data acquisition and processing protocol for a Fourier transform infrared (FT-IR) imaging spectrometer employing a focal plane array (FPA) detector. A model for predicting the signal, noise, and signal-to-noise ratio (SNR) for an FPA in terms of the dynamic range of the analog-to-digital converter (ADC) is presented. Conventional gain ranging theory, modified to account for variation of noise with gain by incorporating a linear model for noise prediction, is shown to provide excellent agreement with observed values for the SNR advantage afforded by gain ranging. SNR improvement, as affected by collection parameters, was shown to be limited by the noise characteristics of the FPA detector. The advantages of gain ranging were demonstrated by spectroscopic imaging of a thin section of human prostate tissue.
Global Phase Angle Description of Generalized Two-Dimensional Correlation Spectroscopy: 2. Its Application to Temperature-Dependent Infrared Spectra of a Langmuir—Blodgett Film of 2-Dodecyl-7,7,8,8-Tetracyanoquinodimethane
Authors: Morita Shin-Ichi , Ozaki Yukihiro , Noda Isao
Published: October 2003

A spectral analysis based on the concept of a global phase map derived from generalized two-dimensional (2D) synchronous and asynchronous correlation spectra has been applied to actual experimental data to demonstrate its potential. As an application of a global 2D phase map, temperature-dependent infrared transmission spectra from 30 to 80 °C of an eleven-layer Langmuir–Blodgett (LB) film of 2-dodecyl-7,7,8,8-tetracyanoquinodimethane (dodecyl-TCNQ) have been investigated. Although the generalized 2D correlation asynchronous map presents only a very weak signal due to the CH3 asymmetric stretching vibration compared with much stronger signals due to the CH2 stretching vibrations of dodecyl-TCNQ, the global 2D phase map clearly shows the distinct nonlinear response arising from the CH3 asymmetric stretching vibration. The detection of nonlinear responses suggests that the active thermal movement of the alkyl-chain loses a trans-zigzag skeleton plane in the intermediate state above 80 °C between the solid and melt states.
Factors Affecting the Production of Fast Transient Signals in Single Shot Laser Ablation Inductively Coupled Plasma Mass Spectrometry
Authors: Leach Andrew M. , Hieftje Gary M.
Published: October 2003

Low sample consumption and high achievable spatial resolution combine to make laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) an attractive direct sampling technique for the analysis of solids. These desirable characteristics are best realized when the laser ablation system is operated in a single-shot fashion, in which each laser pulse produces a transient analyte signal. The temporal width of a single-shot LA analyte transient is inversely related to the best achievable signal-to-noise ratio (S/N). Thus, production of fast transient signals is an important consideration in single-shot LA analyses. In this study we explore the effects on transient pulse width of ablation-cell volume, the diameter and length of tubing used to connect the ablation cell to the ICP, and the composition and flow rate of ablation-cell sweep gas. Minimization of ablation-cell volume and the length and diameter of the transfer tube was found to dramatically decrease the peak widths of transient signals. However, use of helium gas to sweep analyte particles from the ablation cell was found to significantly reduce the effect of cell volume on transient width. Use of a cell volume of 0.70 cm3 and optimization of other instrumental parameters produced a transient sample pulse 85 ms in duration and limits of detection in the tens of femtograms range for single-shot laser-ablation events.
Evaluation of Low-Field Nuclear Magnetic Resonance Spectrometry for At-Line Process Analysis
Authors: Nordon Alison , McGill Colin A. , Littlejohn David
Published: October 2003

A low-field medium-resolution NMR spectrometer, with an operating frequency of 29 MHz for 1H, has been developed for use in process analysis. The information that is attainable at this field strength has been investigated with the use of samples from a wide range of applications including the qualitative monitoring of a benzene production process, the estimation of the average ethoxy chain length in nonyl phenol ethoxylates, and the determination of strong acid concentrations. At low field, the spectra of multi-component samples often exhibit overlapping peaks, so multivariate calibration methods are necessary for quantitative analysis. Simulated data have been used to illustrate the effects of signal-to-noise ratio (SNR), resolution, and line shape on the predictive ability of partial least-squares (PLS) calibration routines, with SNR shown to have a greater impact than resolution on accuracy and precision. PLS calibration models were applied successfully in the analysis of samples from a methacrylamide process and a simulated esterification reaction. The accuracy (<5%) and precision (<3%) were generally good for components at concentrations >1–5% w/w.
Removal of Cosmic Spikes from Hyper-Spectral Images Using a Hybrid Upper-Bound Spectrum Method
Authors: Zhang Dongmao , Ben-Amotz Dor
Published: October 2003

A hybrid of the upper-bound spectrum (UBS), principle component analysis (PCA), and median filter (MF) algorithms is used to efficiently remove cosmic spike spectral artifacts from hyper-spectral data matrices (DM). The resulting UBS-DM method is shown to introduce less spectral distortion than the widely used MF cosmic spike suppression algorithm alone. The new method relies on a truncated series of PCA eigenvectors to produce an upper-bound spectrum, which is in turn used to detect and remove cosmic spikes. The PCA eigenvectors are separated into three groups, each of which is treated in a different manner. The first group of eigenvectors, which contain most of the spectral correlation of interest, are not preprocessed prior to applying the UBS-DM method. The second group, which are more severely contaminated by cosmic spikes (but may also contain important spectral correlations), are MF preprocessed before applying UBS. The third group of eigenvectors, which contain virtually no spectral information, are ignored in regenerating the upper-bound spectra used for spike detection and removal. The UBS-DM algorithm is tested using both synthetic and experimental (iron oxide) Raman hyper-spectral data sets, each containing several thousand spectra, with about 1000 wavelength pixels.
Fourier Deconvolution in Non-Self-Deconvolving Conditions. Effective Narrowing, Signal-to-Noise Degradation, and Curve Fitting
Authors: Lórenz-Fonfría Víctor A. , Villaverde Joaquim , Padrós Esteve
Published: October 2003

The effect of Fourier deconvolution on band narrowing and on the decrease of signal-to-noise ratio has been studied for a generalized case in which the width used in the deconvolution does not match the actual bandwidth. For the identification of underlying component bands, our results show that application of infra-deconvolution (i.e., the bandwidth used for deconvolution is lower than the actual bandwidth) produces a high degradation of the signal-to-noise ratio and poor band narrowing. On the contrary, self- or over-deconvolution, with lower signal-to-noise degradation and higher band narrowing, seem more suitable for this purpose. Relative to quantitative analysis, we rely on both theoretical and practical aspects to propose the generalized use of Voigt band shapes as a fairly correct general model to be used in the curve fitting of deconvoluted bands. With its use, the curve fitting of noise-free deconvoluted bands retrieved the original band parameters with high accuracy. The noise effect on the parameter precision obtained by curve fitting a deconvoluted noisy Lorentzian band was also studied. Finally, the existence of optimum deconvolution parameters for curve fitting complex spectra is considered, and a general recommendation for approaching this optimum is given.
Dual Wavelength Method for Molecular Difference Absorption Measurements in Turbid Media
Authors: Liger Vladimir , Zybin Alexander , Bolshov Mikhail , Niemax Kay
Published: October 2003

A dual wavelength differential absorption method for the detection of inclusions in turbid media is proposed. The method is based on the measurement of the transmitted intensity differences of the two diode lasers tuned to selected wavelengths within a broad absorption band of an inclusion of interest. The strategy for the optimum selection of the diode laser wavelengths and initial adjustment of the detection scheme is developed. It is shown that small deviations in the wavelengths from an optimum position result in a considerably deteriorated background suppression. The method is demonstrated by the detection of two dyes in a small volume inside a phantom filled with a turbid medium with scattering and absorption coefficients similar to those of biological tissues. The type and relative concentrations of the dyes were chosen so that the optical properties at the laser wavelengths are similar to those of a mixture of oxy- and deoxy-hemoglobin. The proposed method is insensitive to inclusions in the test object with spectrally independent scattering and absorption but detects the changes of the dye composition of a few percent inside a small sub-volume. The technique can be useful for the detection of the physiological status and changes in biological tissues.
Surface-Enhanced Raman Spectroscopy in Single Living Cells Using Gold Nanoparticles
Authors: Kneipp Katrin , Haka Abigail S. , Kneipp Harald , Badizadegan Kamran , Yoshizawa Noriko , Boone Charles , Shafer-Peltier Karen E. , Motz Jason T. , Dasari Ramachandra R. , Feld Michael S.
Published: October 2003

Ultrasensitive Raman measurements in single living cells are possible through exploiting the effect of surface-enhanced Raman scattering (SERS). Colloidal gold particles (60 nm in size) that are deposited inside cells as “SERS-active nanostructures” result in strongly enhanced Raman signals of the native chemical constituents of the cells. Particularly strong field enhancement can be observed when gold colloidal particles form colloidal clusters. The strongly enhanced Raman signals allow Raman measurements of a single cell in the 400–1800 cm−1 range with 1-μm lateral resolution in relatively short collection times (1 second for one mapping point) using 3–5 mW near-infrared excitation. SERS mapping over a cell monolayer with 1-μm lateral resolution shows different Raman spectra at almost all places, reflecting the very inhomogeneous chemical constitution of the cells. Colloidal gold supported Raman spectroscopy in living cells provides a tool for sensitive and structurally selective detection of native chemicals inside a cell, such as DNA and phenylalanine, and for monitoring their intracellular distributions. This might open up exciting opportunities for cell biology and biomedical studies.