Showing papers in "Applied Spectroscopy in 2001"
TL;DR: Cervical tissue Raman spectra contain peaks in the vicinity of 1070, 1180, 1195, 1210, 1245, 1330, 1400, 1454, 1505, 1555, 1656, and 1760 cm−1, which means that the ratio of intensities at 1454 to 1656cm−1 is greater for squamous dysplasia than all other tissue types, while the ratio at 1330 to 1454 cm− 1 is lower for samples
Abstract: This study evaluates the potential of near-infrared Raman spectroscopy for in vivo detection of squamous dysplasia, a precursor to cervical cancer A pilot clinical trial was carried out at three clinical sites Raman spectra were measured from one colposcopically normal and one abnormal area of the cervix These sites were then biopsied and submitted for routine histologic analysis Twenty-four evaluable measurements were made in vivo in 13 patients Cervical tissue Raman spectra contain peaks in the vicinity of 1070, 1180, 1195, 1210, 1245, 1330, 1400, 1454, 1505, 1555, 1656, and 1760 cm-1 The ratio of intensities at 1454 to 1656 cm-1 is greater for squamous dysplasia than all other tissue types, while the ratio of intensities at 1330 to 1454 cm-1 is lower for samples with squamous dysplasia than all other tissue types A simple algorithm based on these two intensity ratios separates high-grade squamous dysplasia from all others, misclassifying only one sample Spectra measured in vivo resemble those measured in vitro Cervical epithelial cells may contribute to tissue spectra at 1330 cm-1, a region associated with DNA In contrast, epithelial cells probably do not contribute to tissue spectra at 1454 cm-1, a region associated with collagen and phospholipids
282 citations
198 citations
TL;DR: In this article, the effect of dual-pulse timing on material ablation, plasma temperature, and plasma size for pre-ablation spark dualpulse laser-induced breakdown spectroscopy (LIBS) was investigated.
Abstract: 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
141 citations
TL;DR: In this paper, it was shown that not only the position but also the intensity and shape of the absorption band can vary, depending on the nature of the solvent, and the polarity of a solvent is determined by its solvents.
Abstract: T he term solvatochromism is used to descr ibe the pronounced change in position and sometimes intensity of a UVvisible absorption band following a change in the polarity of the medium. When absorption spectra are measured in solvents of different polarity it is found that not only the position but also the intensity and shape of the absorption band can vary, depending on the nature of the solvent. The in uence of solvents on the course of chemical reactions has been studied for a long time, and efforts have been made to correlate equilibrium constants, reaction rate constants, or positions of ultraviolet absorption bands with the so-called ‘‘polarity’’ of the solvent.1 Attempts made to express the polarity in terms of dielectric constant, dipole moment, or other properties of the solvent have not been very successful, largely due to the simpli cations used. 2 The polarity of a solvent is determined by its sol-
137 citations
TL;DR: In this paper, the authors developed a model to describe the effect of refraction through a planar interface on the collection efficiency and depth of focus when performing confocal Raman microspectroscopy.
Abstract: We have developed a model to describe the effect of refraction through a planar interface on the collection efficiency and depth of focus when performing confocal Raman microspectroscopy. The planar interface introduces spherical aberration, which can substantially degrade the performance of the microscope, especially for large-numerical-aperture microscope objectives. This spherical aberration will increase the range of focal depths spanned by the paraxial and marginal rays of the illuminating laser beam within the sample. In the collection path, it will also distort the scattering volume defined by the confocal aperture; this results in a dramatic fall in the collected light intensity with increasing depth. We demonstrate that there is an optimum numerical aperture for collected light intensity at a given depth. The prediction of this theoretical model is compared to empirical results obtained by mapping the stress distribution within the diamond anvil of a high-pressure cell. Both the collected Raman intensity and the effective depth of focus are compared to the predictions from the theory.
137 citations
TL;DR: The “intrinsic” fluorescence of carboxylate-terminated polyamido amine (PAMAM-CT) dendrimers is studied by two fluorescence techniques—excitation-emission matrices (EEMs) and lifetimes.
Abstract: The "intrinsic" fluorescence of carboxylate-terminated polyamido amine (PAMAM-CT) dendrimers is studied by two fluorescence techniques—excitation-emission matrices (EEMs) and lifetimes. The EEMs show similar spectral profiles for all dendrimer generations (a broad peak with an excitation and emission maximum of 380 and 440 nm, respectively) and an overall increase in relative fluorescence emission with increasing generation. Three distinct, fairly discrete lifetimes are also recovered. The shortest lifetime (0.2–0.4 ns) is a background signal from the solvent. The two longer lifetimes (1.3–2.5 and 4.2–7.1 ns) are attributed to the dendrimer. There is a general shift to longer lifetimes in τ2 and τ3, with increasing generation (Gn). Both lifetimes nearly double in magnitude, going from G2.5 to G7.5, which is indicative of a specific fluorescent component being in a more protected or constrained microenvironment. These results imply that the dendrimer becomes densely packed with increasing generation. The weak, but detectable, fluorescence is most likely due to an n → π* transition from the amido groups throughout the dendritic structure. Even though the exact nature of PAMAM-CT fluorescence is not fully understood, it is clear that this property shows the unique aspects of the architecture of these dendrimers and can be utilized in their characterization.
127 citations
TL;DR: In this article, it has been known for many years that it should be possible to discriminate between Raman and fluorescence phenomena on the basis of their differing temporal responses, but it is only relatively recently that optical technology has advanced sufficiently to achieve the necessary combination of high repetition rate and picosecond laser pulses, coupled with
Abstract: It has been known for many years that it should be possible to discriminate between Raman and fluorescence phenomena on the basis of their differing temporal responses. However, it is only relatively recently that optical technology has advanced sufficiently to achieve the necessary combination of high repetition rate and picosecond laser pulses, coupled with
125 citations
TL;DR: In this article, the optimal temporal gating for laser-induced breakdown spectroscopy (LIBS) analysis was investigated for a select group of toxic metals, namely the Resource Conservation and Recovery Act (RCRA) metals arsenic, beryllium, cadmium, chromium, lead, and mercury.
Abstract: Optimal temporal gating for laser-induced breakdown spectroscopy (LIBS) analysis was investigated for a select group of toxic metals, namely the Resource Conservation and Recovery Act (RCRA) metals arsenic, beryllium, cadmium, chromium, lead, and mercury. The differing rates of decay between the continuum plasma emission and the atomic emission were used as a means to maximize the signal-to-noise ratio of the atomic emission lines for these six metal species. Detection windows were investigated corresponding to delay times from 2 to 50 μs following the plasma-initiating laser pulse. For the current experimental conditions, it is concluded that the relatively short delay time of 12 μs is optimal for the detection of arsenic, beryllium, cadmium, and mercury, while a longer delay time of 50 μs is optimal for the detection of chromium and lead. The reduced atomic emission intensity at relatively long delay times is compensated for by the use of long detector gate widths. Estimated detection limits are reporte...
107 citations
TL;DR: In this article, a multiple time-gate fluorescence lifetime acquisition module is presented, which enables the recording of fluorescence lifetimes by capturing the intensity decay in four or eight time gates.
Abstract: A versatile multiple time-gate fluorescence lifetime acquisition module is presented. The module is used as an add-on to a two-photon scanning laser microscope equipped with pulsed excitation for fluorescence lifetime imaging. It enables the recording of fluorescence lifetimes by capturing the intensity decay in four or eight time gates. The module allows fluorescence lifetime imaging at high count rates and with a high efficiency. The module is equipped with computer-controlled variable-delay lines for setting the gate widths. Decay times can be accurately measured in the 0.5 ns–1 μs range. Fluorescence lifetime imaging experiments on a number of single dye solutions with different (mono-exponential) fluorescence lifetimes are in excellent agreement with the reference values obtained with time-correlated single photon counting. Measurements on a test specimen exhibiting a bi-exponential decay demonstrate that the two decay components can be quantified with high accuracy. In a specimen containing six different lifetimes, in the range 2.8 to 12 ns, all lifetimes could be well distinguished. As an example, the results of a pH imaging experiment on oral biofilm using carboxyfluorescein are presented. Here, fluorescence lifetime imaging is used both to separate the short-lifetime autofluorescence from the carboxy-fluorescein fluorescence and to determine the pH in the biofilm.
106 citations
TL;DR: In this article, the authors used the temporal dispersion of a short laser pulse injected into the probed medium to measure the mean values of the absorption and reduced scattering coefficients of the medium.
Abstract: Time-resolved reflectance has been used for the nondestructive measurement of optical properties in apples. The technique is based on the detection of the temporal dispersion of a short laser pulse injected into the probed medium. The time distribution of re-emitted photons interpreted with a solution of the diffusion equation yields the mean values of the absorption and reduced scattering coefficients of the medium. The proposed technique proved useful for the measurement of the absorption and scattering spectra of different varieties of apples, revealing the spectral shape of chlorophyll. No major variations were observed in the experimental data when the fruit was peeled, showing that the optical properties measured were those of the pulp. With this technique the change in chlorophyll absorption during storage and ripening could be followed. Finally, a compact prototype working at few selected wavelengths was designed and constructed, demonstrating potentialities of the technique for industrial applications.
106 citations
TL;DR: In this paper, the authors used an infrared microscope and a focal plane array to perform total internal reflection (ATR) infrared mapping micro-spectroscopy using an infrared camera.
Abstract: Attenuated total internal reflection (ATR) infrared mapping microspectroscopy using an infrared microscope and a focal plane array is investigated and reported. The study demonstrates the advantages of conducting ATR microspectroscopy using a focal plane array detector. These benefits include the rapid acquisition of molecular specific images, ease of sample preparation, and increased spatial resolution. An experimental determination of the spatial resolution found that the combined system operates very close to the diffraction limit, and a 4× magnification factor associated with the germanium internal reflection element was realized. Experiments conducted on several polymer samples and a biological sample demonstrate the future viability of the method.
TL;DR: In this article, the effect of laser energy on laser-induced breakdown emission intensity and average temperature in a short-pulse plasma generated by using 140 fs laser excitation was investigated.
Abstract: In this paper, we investigate the effect of laser energy on laserinduced breakdown emission intensity and average temperature in a short-pulse plasma generated by using 140 fs laser excitation. Both line emission and continuum background intensity and plasma temperature decrease very rapidly after excitation compared to the more conventional nanosecond pulse excitation. Both emission intensity and plasma temperature increase with increasing laser energy. However, the intensity increase appears to be mostly related to the amount of material ablated. Also, nongated laser-induced breakdown spectroscopy (LIBS) is demonstrated using a high-pulse (1 kHz) pulse repetition rate.
TL;DR: In this article, a 1.3 ps laser pulse was used on glass, steel, and copper to measure laser-induced breakdown spectra on three samples, and the background was low enough that excellent LIBS spectra were obtained on the three samples.
Abstract: Laser-induced breakdown spectra were measured by using a 1.3 ps laser pulse on glass, steel, and copper. Material ablation with the use of picosecond excitation is very precise with well-formed sharpedged craters. The spectra obtained with 570 nm, 1.3 ps excitation decay more quickly and show significantly lower background emission than those that use 1064 nm, ∼7 ns excitation. The background was low enough that excellent laser-induced spectroscopy (LIBS) spectra were obtained on the three samples by using a single 1.3 ps laser pulse and a nongated detector. Similar results were obtained by using nanosecond excitation but with higher relative background signals. The radiance was similar with the use of pico- or nanosecond excitation; however, the radiant intensity was larger with nanosecond excitation because of the larger plasma.
TL;DR: In this paper, the spectral features identified by the pattern recognition GA allow the wood samples to cluster by type in a plot of the two largest principal components of the data, and the bulk of the information encoded by these spectral features is about differences between wood types.
Abstract: Raman spectroscopy and pattern recognition techniques are used to develop a potential method to characterize wood by type. The test data consists of 98 Raman spectra of temperate softwoods and hardwoods, and Brazilian and Honduran tropical woods. A genetic algorithm (GA) is used to extract features (i.e., line intensities at specific wavelengths) characteristic of the Raman profile of each wood-type. The spectral features identified by the pattern recognition GA allow the wood samples to cluster by type in a plot of the two largest principal components of the data. Because principal components maximize variance, the bulk of the information encoded by these spectral features is about differences between wood types. The predictive ability of the descriptors identified by the pattern recognition GA and the principal component map associated with them is validated using an external prediction set consisting of tropical woods and temperate hard and softwoods.
TL;DR: In this article, the feasibility of using laser-induced plasma spectroscopy (LIPS) as a rapid and simple method to analyze fluorine, chlorine, and bromine in solid organic compounds was investigated.
Abstract: The feasibility of using laser-induced plasma spectroscopy (LIPS) as a rapid and simple method to analyze fluorine, chlorine, and bromine in solid organic compounds was investigated. A Nd:YAG laser at 1064 nm with pulse energy of 100 mJ was used to produce the plasma. This method presents many advantages for the determination of halogens in organic compounds, including very simple sample preparation and near-real-time analysis. Solid organic compounds were measured in air and helium atmospheres. Carbon in organic compounds was chosen as the internal standard for the measurement of F, Cl, and Br. Linear responses for these elements were obtained for both atmospheres. However, the sensitivity was much higher and the background noise was much lower in the helium atmosphere.
TL;DR: In this article, the root mean square error of prediction (RMSEP) was used for calibration transfer between pairs of spectrometers from a group of diffraction grating-based instruments for noninvasive prediction of soluble solid content of melon fruit.
Abstract: In near-infrared (NIR) spectroscopy, the transfer of predictive models between Fourier transform near-infrared (FT-NIR) and scanning-grating-based instruments has been accomplished on relatively dry samples (<10% water) using various chemometric techniques - for example, slope and bias correction (SBC), direct standardization (DS), piecewise direct standardization (PDS), orthogonal signal correction (OSC), finite impulse transform (FIR) and wavelet transform (WT), and application of neural networks. In this study, seven well-known techniques [SBC, DS, PDS, double-window PDS (DWPDS), OSC, FIR, and WT], a photometric response correction and wavelength interpolative method, and a model updating method were assessed in terms of root mean square error of prediction (RMSEP) (using Fearn's significance testing) for calibration transfer (standardization) between pairs of spectrometers from a group of four spectrometers for noninvasive prediction of soluble solid content (SSC) of melon fruit. The spectrometers were diffraction grating-based instruments incorporating photodiode array photodetectors (MMS1, Carl Zeiss, Jena, Germany), used with a standard optical geometry of sample, light source, and spectrometer. A modified WT method performed significantly better than all other standardization methods and on a par with model updating.
TL;DR: In this paper, the authors discuss polycyclic aromatic hydrocarbons and Polycyclic Aromatic Hydrocarbons (PAAH) with respect to their properties.
Abstract: 44. K. W. Street, Jr., W. E. Acree, Jr., J. C. Fetzer, P. H. Shet, and C. F. Poole, Appl. Spectrosc. 43, 1149 (1989). 45. S. A. Tucker, L. E. Cretella, R. Waris, K. W. Street, Jr., W. E. Acree, Jr., and J. C. Fetzer, Appl. Spectrosc. 44, 269 (1990). 46. U. Breymann, H. Dreeskamp, E. Koch, and M. Zander, Chem. Phys. Lett. 59, 68 (1978). 47. S. A. Tucker, J. M. Grif n, W. E. Acree, Jr., P. P. Mulder, J. Lugtenburg, and J. Cornelisse, Analyst (Cambridge, U.K.) 119, 2129 (1994). 48. L. C. Sander and S. A. Wise, Polycyclic Aromatic Hydrocarbon (NIST Special Publication 922, Washington, 1997). 49. S. L. Murov, I. Carmichael, and G. L. Hug, Handbook of Photochemistry (Marcel Dekker, New York, 1993), 2nd ed.
TL;DR: In this paper, the authors used FT-Raman spectroscopy for the quantitative determination of ciprofloxacin in pharmaceutical solid dosage forms, and the results were in good agreement with the results obtained by the current United States Pharmacopoeia and National Formulary (NF 19) method.
Abstract: FT-Raman spectroscopy based on band intensity or band area measurements was used for the quantitative determination of ciprofloxacin in pharmaceutical solid dosage forms. Univariate calibration was used for quantitative analysis. Bands observed at 1708, 1624, 1548, 1493, 1273, 1253, 1238, 1024, 805, 787, 752, 718, 665, and 638 cm-1 were used. Calibration curves were linear in the concentration range of 3-100% w/w with correlation coefficients of 0.99-0.996 and 0.991-0.9993 for band intensity and band area measurements, respectively. Precision ranged from 0-11 and 0.4-12% relative standard deviation (RSD) (n = 3) for band intensity and band area measurements, respectively, and results were in good agreement with the results obtained by the current United States Pharmacopoeia (USP 24) and National Formulary (NF 19) method. Multivariate calibration was also used for quantitative analysis. Multiple linear regression using the intensities of the 1545 and 1272 cm-1 bands gave results in accordance with those obtained by the current United States Pharmacopoeia (USP 24) and National Formulary (NF 19) method. As measurement takes just 30 s using the analytical readout from a single band, the proposed method can be used to replace tedious and time-consuming methods.
TL;DR: Fajardo et al. as discussed by the authors proposed a method for determining the thickness of a cryogenic parahydrogen (pH2) solid from its infrared (IR) absorption spectrum.
Abstract: We present a convenient method for determining the thickness of a cryogenic parahydrogen (pH2) solid from its infrared (IR) absorption spectrum. Millimeters-thick pH2 solids of exceptional optical clarity can be produced by the rapid vapor deposition method [M.E. Fajardo and S. Tam, J. Chem. Phys. 108, 4237 (1998)]. Doping of these pH2 solids is readily accomplished by co-deposition of the desired impurities, making them excellent hosts for high-resolution matrix isolation spectroscopy. The intensities of the IR "double" transitions Q1(0) + S0(0) and S1(0) + S0(0) of the pH2 host are insensitive to the matrix microstructure and to the presence of dopants, so these absorptions are especially well suited for thickness determinations. We calibrate the integrated absorption intensities of these two bands against the sample thicknesses determined from transmission interference fringes appearing in the same experimental spectra; we report: αtilde[Q1(0) + S0(0)] = 4.84(±0.18) × 10-14 cm3/s, and αtilde[S1(0) + S0(0)] = 0.35(±0.02) × 10-14 cm3/s (95% confidence). We also discuss several other advantages of rapid-vapor-deposited pH2 solids as hosts for quantitative IR absorption spectroscopy of dopant species.
TL;DR: In this paper, the authors developed expressions for the Raman power emitted by liquid core optical fiber (LCOF) sample cells in six simple excitation/collection geometries and the fraction of that power that can be utilized in a conventional Raman spectrometer.
Abstract: This paper develops expressions for the Raman power emitted by liquid core optical fiber (LCOF) sample cells in six simple excitation/collection geometries and the fraction of that power that can be utilized in a conventional Raman spectrometer From these expressions a "figure of merit" is developed that can be used to predict the relative intensity enhancement provided by LCOFs having different inside diameters and loss characteristics For the apparatus used here, we show theoretically and experimentally that the figure of merit takes the simple form (αd)-1 where α and d are, respectively, the loss coefficient and inside diameter of the LCOF Given the varying optical quality of Teflon®-AF LCOFs currently in use, the analysis presented here should be useful in optimizing the performance of LCOF accessories in Raman and related spectroscopic applications
TL;DR: In this paper, a population of 67 individual urine samples from children and adults, collected over 24 hours, was analyzed for urea, creatinine, uric acid, glucose, total protein, phosphate, and sulfate by using clinical reference methodology.
Abstract: The reagent-free multicomponent analysis of components in urine using mid-infrared spectroscopy possesses many attractions. A population of 67 individual urine samples from children and adults, collected over 24 h, was analyzed for urea, creatinine, uric acid, glucose, total protein, phosphate, and sulfate by using clinical reference methodology. The urine pH value was potentiometrically measured by a glass electrode. Partial least-squares (PLS) calibration models were calculated over optimized, component-specific ranges from attenuated total reflection spectra of the urine samples measured by a micro-Circle cell. Apart from glucose and total protein, for which the spread in urine sample concentrations was too small, calibrations were successful for metabolites such as urea, creatinine, and uric acid. Additionally, concentrations of sulfate and phosphate anions, which show significant mid-infrared absorption bands, could also be quantified. The acid secreted with the urine influences the equilibrium between di- and monobasic phosphate in this biofluid, which is used as the spectroscopic basis for the pH assay presented here. The analytical performance of the reference methods is discussed with regard to evaluating the limitations of the spectroscopic assay. Additionally, aqueous solutions of individual urine components with a spread of concentrations similar to those found in native urine samples were analyzed by using PLS calibrations.
TL;DR: In this article, the PACLS/PLS hybrid algorithm was used for near-infrared spectra of dilute aqueous solutions containing the analytes urea, creatinine, and NaCl.
Abstract: A new classical least-squares/partial least-squares (CLS/PLS) hybrid algorithm has been developed that demonstrates the best features of both the CLS and PLS algorithms during the analysis of spectroscopic data. By adding our recently reported prediction-augmented classical least-squares (PACLS) to the hybrid algorithm, we have the additional benefit that known or empirically derived spectral shape information can be incorporated into the hybrid algorithm to correct for the presence of unmodeled sources of spectral variation. A detailed step-by-step description of the new hybrid algorithm in calibration and prediction is presented. The powerful capabilities of the new PACLS/PLS hybrid are demonstrated for near-infrared spectra of dilute aqueous solutions containing the analytes urea, creatinine, and NaCl. The PACLS/PLS method is demonstrated to correct the detrimental effects of unmodeled solution temperature changes and spectrometer drift in the multivariate spectral calibration models. Initially, PLS and PACLS/PLS predictions of analytes from variable-temperature solution spectra were made with models based upon spectra previously taken of the samples at constant temperature. The presence of unmodeled temperature variations and system drift caused the prediction errors from these models to be inflated by more than an order of magnitude relative to the cross-validated errors from the calibrations. PLS achieved improved predictions of the variable-temperature spectra by adding spectra of a few variable-temperature samples into the original calibration data followed by recalibration. PACLS/PLS predictions were corrected for temperature variations and system drift by adding spectral differences of the same subset of samples collected under constant- and variable-temperature conditions to the PACLS prediction portion of the hybrid algorithm during either calibration or prediction. Comparisons of the prediction ability of the hybrid algorithm relative to the PLS method using the same calibration and subset information demonstrated hybrid prediction improvements that were significant at least at the 0.01 level for all three analytes. The new hybrid algorithm has widespread uses, some of which are also discussed in the paper.
TL;DR: In this article, two variations on polynomial curve fitting through a least-squares calculation are used to remove nonlinear background and high-spatial-frequency noise components from Raman spectra.
Abstract: A study has been made of the use of polynomial curve fitting for removal of nonlinear background and high-spatial-frequency noise components from Raman spectra. Two variations on polynomial curve fitting through a least-squares calculation are used. One, involving fitting data x values to corresponding y values, was used to approximate background functions, which are subtracted from the original data. For smoothing, a reference matrix of six vectors that contains a unity d.c. level, a ramp made up of x values, a quadratic made up of x2 values, etc., is fitted to a section of data. The reference vectors are scaled by the fit values and added to give the smoothed estimate of a spectral peak. It is demonstrated, with factor analysis as a test procedure, that the background removal procedure does remove nonlinearities that were present in the original data. The smoothing procedure rejects high-spatial-frequency noise without introducing detectable nonlinearities.
TL;DR: In this paper, the vibrational molecular spectroscopic study of L-phenylalanine in aqueous solution was carried out in the pH range 0-13 and the results showed that the amino acid undergoes structural changes under the influence of pH.
Abstract: Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectra of L-phenylalanine in aqueous solution were recorded in the pH range 0-13. The vibrational molecular spectroscopic study of this amino-acid, a well-known component of human tissue, showed that L-phenylalanine undergoes structural changes under the influence of pH. Characteristic bands of each ionic species were highlighted and the pKa values were determined from IR measurements by using an intensity ratio method. ATR-FTIR spectroscopy appears to be a powerful tool for obtaining valuable information on the building blocks of proteins and for measuring tissue damage in aqueous environments.
TL;DR: In this article, a multispectral imaging in combination with SIMCA classification was used for automatic detection of parasitic worms in fillets of commercially important fish species, and the results indicated that the spectral characteristics of nematodes differ sufficiently from those of fish flesh to allow one to obtain fairly good classifications.
Abstract: 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.
TL;DR: In this paper, the FT-IR method was used to determine the boron content and degree of hydrolysis of esters, as well as the most important parameters affecting the water absorption capacity of a brake.
Abstract: The free water content gradually increased, and it achieved a reaction balance between the reactants after ;5% of water was added into the studied system at the borate content equivalent to 2.2 wt % of boron. The hydrolytic conversion in relation to the amount of water added to the model 3,6,9-trioxadecanol/borate mixture, at the borate content equivalent to 2.2 wt % of boron, is presented in Fig. 4. Such a relationship between the amount of absorbed external water and its hydrolytical conversion can be a convenient criterion in the quality control of brake uid formulations and is easily measured by this method. As mentioned earlier, the location of the band speci c for the borate ester changes from 663 cm21 up to 675 cm21. This pattern was also monitored for the above series of samples prepared (Fig. 5). It was con rmed that hydrolysis of the boron esters is parametrically related to the position of the BO3 band in its FT-IR spectrum and may be used for quantitative interpretation. The above ndings suggest that the proposed FT-IR method makes possible a one-step determination of water content and of borate components in a brake uid formulation. It provides a fast and easy procedure for determination of the borate content and degree of hydrolysis of esters, as the most important parameters affecting the water absorption capacity of a brake uid. As a result, it is possible to investigate the tendency of external water adsorption, the bound volume of water, and the amount of boron.
TL;DR: In this article, multiresolution wavelet transformation (MWT) and block thresholding is used to effectively suppress both background and noise interference while minimally distorting Raman spectral features.
Abstract: Multiresolution wavelet transformation (MWT) and block thresholding is used to effectively suppress both background and noise interference while minimally distorting Raman spectral features. The performance of MWT as a spectral pre-processing algorithm is demonstrated using both synthetic spectra and experimental hyper-spectral Raman images with large background and noise components. The results are quantified by comparing correlation coefficients of synthetic spectra with either the same or different backgrounds. The improved chemical imaging performance obtained using MWT is demonstrated by comparing principal component analysis (PCA) channel images and spectral angle mapping (SAM) classified images before and after MWT pre-processing.
TL;DR: In this paper, the spectral data were classified by the application of soft independent modeling of class analogies (SIMCA), using principal components analysis (PCA) to estimate the distance of separation between the different classes of paper samples and discriminant analysis (DA) to obtain a probabilistic classification.
Abstract: Infrared (IR) spectra of different varieties of document papers were collected with the use of attenuated total reflectance (ATR, 4000-650 cm-1, eight paper varieties) and diffuse reflectance (DRIFTS, 9000-2500 cm-1, six paper varieties) techniques. The spectral data were classified by the application of soft independent modeling of class analogies (SIMCA), using principal components analysis (PCA) to estimate the distance of separation between the different classes of paper samples and discriminant analysis (DA) to obtain a probabilistic classification. The use of DA on spectral data needed a preliminary data reduction step, either by PCA-decomposition of spectra or the selection of discrete spectral features having maximum discriminating ability. The aim of this research was to evaluate these data-reduction techniques and compare the discriminating power of these two spectral techniques (DRIFTS and ATR) by the application of PCA and DA. The use of PCA scores as DA variables provided the best resolution (100% correct classification) for the DRIFTS spectra, while PCA on the ATR spectra resulted in the best discrimination, separating 67.86% paper pairs completely with the use of cross-validation. The results of this study reemphasize that infrared spectroscopy coupled with multivariate statistical methods of analysis could provide a powerful discriminating tool for the forensic questioned document examiner.
TL;DR: In this paper, a specific method of sample preparation based on a filtration and deposition-evaporation sequence is proposed, which permits the separation and preconcentration of the synthetic polymer that is being analyzed and avoids problems arising from the simultaneous interpretation of IR spectra obtained from complex mixtures of organic and inorganic compounds present in small artistic samples.
Abstract: Differentiation between the synthetic polymers used in former restorations of works of art and the original materials used by the artist is of great interest; such differentiation is needed to establish an adequate process of restoration for the work of art A specific method of sample preparation based on a filtration and deposition-evaporation sequence is proposed, which permits the separation and preconcentration of the synthetic polymer that is being analyzed and avoids problems arising from the simultaneous interpretation of IR spectra obtained from complex mixtures of organic and inorganic compounds present in small artistic samples In addition to the identification of characteristic IR absorption bands, quantitative diagnostic criteria based on two-dimensional diagrams of relative intensity of selected peaks have been developed Standards of acrylic, alkyd, cellulose nitrate, epoxy, ketone, poly(vinyl acetate), polyurethane, silicone synthetic polymers and semi-synthetic wax used as binding media, adhesives, and coatings have been prepared by this proposed experimental procedure, and IR spectra have been obtained Finally, several samples from paintings and artistic objects dating from the 16th to the 20th century have been analyzed, and synthetic and semi-synthetic organic materials have been successfully identified by comparison with the standards using the proposed method of analysis
TL;DR: In this article, a global phase map derived from generalized two-dimensional synchronous and asynchronous correlation spectra is introduced to extract the purely correlational information by intentionally canceling amplitude information.
Abstract: The concept of a global phase map derived from generalized two-dimensional synchronous and asynchronous correlation spectra is introduced to extract the purely correlational information by intentionally canceling amplitude information. For the practical usage of a global 2D phase map, a filtering method based on the standard deviation spectrum obtained from the time series intensity profiles is proposed to remove the effect of small amplitude noise. A simulation created with the use of three synthesized bands with exponential decay has clearly detected the only difference in the characteristic rate constant of the decay process in the global 2D phase map, although the three bands have different initial values of the peak intensity amplitudes.