bluuebunny/crossref_metadata_2025 huggingface dataset:
Alleviating the Effects of Light Scattering in Multivariate Calibration of Near-Infrared Spectra by Path Length Distribution Correction
Authors: Leger Marc N.
Published: October 2010

Near-infrared (NIR) spectroscopy has been used for noninvasive measurements of solid and liquid samples, through highly scattering media such as colloids, food, and tissue. It has seen many applications in agriculture, medicine, and petroleum industries, mainly due to the minimal sample preparation that is required. This minimal sample preparation does come at a cost to the analyst, since the high signal-to-noise ratio of a typical NIR instrument can be riddled with effects stemming from heterogeneity and the scattering of light. This work proposes a novel preprocessing method, the path length distribution correction (PDC) method, to correct spectral nonlinearities in samples of highly scattering media. These nonlinearities stem from the distribution of path lengths of the incident light, which are a result of the scattering of light in the sample. Recent developments in time-of-flight (TOF) spectroscopy have allowed for the acquisition of the distribution of times that photons travel within a sample simultaneous with the collection of the NIR spectrum. The TOF distribution is used to estimate a path length distribution within a sample, which is then used to fix the measurement spectra, giving each spectrum an apparent path length of unity. The PDC-corrected spectra can then be used with traditional multivariate calibration methods such as principal component regression (PCR) and partial least squares (PLS). Another discussion looks at the viability of using a lognormal distribution as a simple approximation of the TOF distribution. This would be very useful in circumstances in which experimental TOF distributions are not collected. PDC is shown to significantly improve prediction errors in experimental data sets, while diagnostic plots indicate that the corrected spectra do appear to have a path length of unity, thus alleviating effects of the distribution of path lengths.
Evaporation and Condensation of SiO and SiO2 Studied by Infrared Spectroscopy
Authors: Klevenz M. , Wetzel S. , Möller M. , Pucci A.
Published: October 2010

Physical evaporation of SiO and SiO2 under ultra-high vacuum conditions was monitored in situ with infrared spectroscopy at frequencies between 450 cm−1 and 5000 cm−1. The measured vibrational spectra of the condensed films are identical in both cases, for SiO and SiO2 evaporation, and can be described with four Brendel oscillators located at 380 cm−1, 713 cm−1, 982 cm−1, and 1101 cm−1, corresponding to typical vibration modes in SiO.
Attenuated Total Reflection Fourier Transform Infrared Spectroscopic Investigation of the Postmortem Metabolic Process in Rat and Human Kidney Cortex
Authors: Tuo Ya , Huang Ping , Ke Yong , Fan Shuanliang , Lu Qinyang , Xin Bo , Wang Zhenyuan
Published: October 2010

Attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy has been applied to study the short and long term postmortem metabolic processes in rat and human kidney cortexes. The goals of this project were as follows: (1) to investigate the changes of ATR spectra in different rat and human tissues after death, (2) to explore the best mathematical model with different band absorption ratio changes to determine the postmortem interval (PMI), and (3) to establish a preliminary human postmortem ATR spectra database. There were three different types of metabolic changes after death based on the spectral results: (1) the intensities of some bands increased continuously (e. g., C–H stretching region), (2) the intensities of other bands decreased continuously (e.g., PO2− symmetric stretching), and (3) other bands remained relatively stable (e.g., C–OH bending, CO–O–C antisymmetric stretching). The band absorbance ratios for rats were found to display either a significant increase or decrease with increasing time after death. Of the absorbance ratios of the various bands investigated to find the best fit with the cubic model function in rats, the A1652/ A1396 ratio showed the strongest correlation ( R2 = 0.937). Comparison of the rat kidney cortex spectra with selected human postmortem cases showed similar postmortem metabolic changes. In conclusion, ATR FT-IR spectroscopy was shown to be a convenient and reliable method of determining short and long term postmortem intervals by simultaneously monitoring several specific parameters, although these observations have yet to be applied at forensic scenes by further field studies.
Simple in Situ Monitoring of a Complex Catalytic Reaction Network at High Pressure by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy
Authors: Andanson Jean-Michel , Jutz Fabian , Baiker Alfons
Published: October 2010

Attenuated total reflection (ATR) Fourier transform infrared (FT-IR) in situ measurements were performed during the catalytic hydrogenation of acetophenone under high pressure (5.0 MPa). The catalyst used was a suspension of rhodium nanoparticles in an ionic liquid. At the highest temperature used (80 °C), the selectivity of the hydrogenation to 1-phenylethanol dropped from 80% in the beginning of the reaction, when acetylcyclohexane was the main side product, to less than 50% after a few hours of experiment because of the consecutive hydrogenation of 1-phenylethanol to ethylcyclohexane. The evolution of the concentrations of reactant and products was quantified using flawless spectra of pure components with a classical least squares (CLS) multivariate method applied to several ranges of the mid-infrared spectra. The only variable parameters of the analysis are the concentrations of each component themselves and the baseline shift of the spectrum during the reaction. The advantage of using multivariate analysis over the analysis of a single vibrational band, as well as the limitations of this type of spectral analysis, are discussed.
A New Method for Determination of Self-Absorption Coefficients of Emission Lines in Laser-Induced Breakdown Spectroscopy Experiments
Authors: Bredice Fausto O. , Rocco Héctor O. Di , Sobral Hugo M. , Villagrán-Muniz Mayo , Palleschi Vincenzo
Published: October 2010

In this paper we present a new method for determining the self-absorption coefficients of emission lines in laser-induced breakdown spectroscopy (LIBS) experiments. With respect to other methods already present in the literature, the proposed approach has the advantage of not requiring, providing some conditions are fulfilled, any knowledge of the plasma parameters such as temperature and electron number density and of the emission line spectral coefficients such as transition probability. An example of the application of the approach is given for emission lines measured at different delay times after laser ablation of a silver target.
Development of a Non-Scanning Vibrational Sum-Frequency Generation Detected Infrared Super-Resolution Microscope and its Application to Biological Cells
Authors: Inoue Keiichi , Fujii Masaaki , Sakai Makoto
Published: October 2010

We report single-cell infrared (IR) imaging of onion ( Allium cepa) root cells using an IR super-resolution microscope based on vibrational sum-frequency generation (VSFG). The resolution of recorded IR images was less than 2 μm and IR super-resolution was achieved by virtue of the VSFG detection. In addition, IR spectra measurements were successfully performed on distinct intra-cellular assemblies. The IR absorption intensity of the cell nuclear edge and the nucleolus in the 3055–3130 cm−1 region was stronger than that from the cytoplasmic part. This is because the cell nucleus and nucleolus contain larger amounts of nucleic acid. Thus, the obtained IR spectra reflect differences in chemical composition among different cellular structures. In addition, the ability of our novel IR super-resolution microscope to obtain distinct information on both VSFG and two-photon fluorescence is demonstrated.
Fourier Transform Infrared Photoacoustic Multicomponent Gas Spectroscopy with Optical Cantilever Detection
Authors: Hirschmann Christian Bernd , Uotila Juho , Ojala Satu , Tenhunen Jussi , Keiski Riitta Liisa
Published: October 2010

The sensitivity of photoacoustic spectroscopy was improved with the invention of optical cantilever detection (PAS-OCD). However, the ability of present PAS-OCD devices to carry out multicomponent detection is poor. To overcome this, a Fourier transform infrared photoacoustic spectrometer with optical cantilever detection (FT-IR-PAS-OCD) prototype was assembled. In this article, the first evaluation and performance tests of the prototype are described. Selectivity, sensitivity, and the linearity of the signal response are evaluated. The linear response was studied for methane and carbon dioxide and confirmed in the whole analyzed concentration range from 500 to 3500 ppm and from 2500 to 17500 ppm, respectively. The calculated signal-to-noise ratio (SNR) and limit of detection were 2027 and 0.5 ppm for methane and 1362 and 4 ppm for carbon dioxide, with a measurement time of 100 seconds. Selectivity was studied with a multicomponent gas mixture of propene, methane, carbon dioxide, and methylmercaptane. The results indicate that a quantitative analysis of all components in the mixture is possible using the FT-IR-PAS-OCD.
Lean Raman Imaging for Rapid Assessment of Homogeneity in Pharmaceutical Formulations
Authors: Brown Stephanie C. , Claybourn Mike , Sievwright Dawn , Fearnside Vicki , Ashman Chris
Published: October 2010

Solid dispersion formulations and drug in polymer matrices are increasingly being used by the pharmaceutical industry to enhance the solubility, or bio-availability, of active pharmaceutical ingredients (APIs). The degree of solubility or bio-availability enhancement, as well as properties such as chemical stability and physical characteristics, will be dependent on the homogeneity of the drug in polymer matrix. The use of Raman spectroscopy to assess homogeneity has traditionally been limited by the time required to acquire images from a statistically representative sample area. This may be overcome by employing a more rapid one-dimensional Raman line-mapping approach and using a statistical analysis to extract the critical information. This approach has been termed “lean” Raman imaging and allows a large area of sample to be probed in a relatively short space of time. This paper discusses the use of “lean” Raman imaging to assess two performance-indicating parameters of a drug in polymer formulation, sedimentation of the API within a capsule formulation and phase separation of the individual components. The development of a screening method, using Raman line mapping to allow rapid measurement of sedimentation of the API, is discussed. This method requires less than half an hour per capsule for data collection and processing. In addition, the development of a “lean” Raman mapping technique, using single line scans to assess drug and polymer domain sizes, is detailed. This technique employs a simple peak ratio approach coupled with statistical analysis to provide a measure of the degree of drug and polymer segregation without the need for acquisition of high pixel density images or multivariate analysis. The Raman mapping data is compared with both the dissolution profiles and processing parameters of the samples tested and a strong correlation is shown between formulation homogeneity and dissolution behavior.
Probe-Dependent Microenvironments within Biodegradable Films Formed from Poly(L-Lactic Acid) and Pluronic 104
Authors: Tan Loraine T. , Holthoff William G. , Steves Jordan M. , Bright Frank V.
Published: October 2010

We report on the local microenvironment surrounding three small fluorescent probe molecules (pyrene, [6-propionyl-2-( N, N-dimethylamino) naphthalene] (PRODAN), and [4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4 H-pyran] (DCM)) when they are sequestered at low concentration within thin biodegradable films formed from poly( L-lactic acid) (PLLA) and Pluronic P104 blends. Despite each probe molecule being neutral, they sense and report from much different microenvironments in comparison to each other. Specifically, the nonpolar pyrene probe senses a slightly more polar microenvironment as the PLLA content in the polymer blend increases. In contrast, the polar PRODAN and DCM probes sense less polar microenvironments as the PLLA content within the polymer blend increases. Time-resolved fluorescence intensity decay experiments on pure PLLA films reveal that each probe molecule encounters significant heterogeneity. Pyrene emits simultaneously from three discrete microenvironments. This is consistent with pyrene molecules reporting from crystalline, amorphous-crystalline intermediate, and amorphous regions. PRODAN and DCM appear to emit from a continuum of microenvironments. These results have ramifications on the performance of biodegradable drug delivery platforms loaded with small drug molecules.
Two-Photon Absorption in Rhodamine 6G Occurring in Concert with Fluorescence Depletion
Authors: Iketaki Yoshinori , Watanabe Takeshi
Published: October 2010

Using two-color fluorescence dip spectroscopy, we observed two-photon absorption processes (TPA) in Rhodamine 6G occurring in concert with fluorescence depletion processes (FD). A nano-second pulse erase beam in the near-infrared region was applied to induce TPA together with FD. It was found that the fluorescence intensity strongly depends on the photon-flux of the erase beam and that the effective TPA cross-section for the nano-second laser pulse is smaller than that for a femto-second laser pulse. This phenomenon can be interpreted as resulting from FD induced by a multiple-excitation process.
Morphology-Based Automated Baseline Removal for Raman Spectra of Artistic Pigments
Authors: Perez-Pueyo Rosanna , Soneira Maria Jose , Ruiz-Moreno Sergio
Published: October 2010

The interpretation of a Raman spectrum is based on the identification of its characteristic molecular bands. However, the assignment of the vibrational modes is often compromised by the presence in the spectrum of an intense fluorescence background that covers the measured spectra. Several techniques have been employed to minimize the presence of this fluorescence in order to resolve and analyze Raman spectra. In this paper a new automated method for fluorescence subtraction is described, based on morphology operations. This method is compared with the most commonly used polynomial fitting methods. Results indicate that the proposed automated method is efficient in fluorescence subtraction and retains the line shapes and positions of the Raman bands in the spectra.
Calibration Transfer from Dispersive Instruments to Handheld Spectrometers
Authors: Pierna Juan Antonio Fernández , Vermeulen Philippe , Lecler Bernard , Baeten Vincent , Dardenne Pierre
Published: October 2010

The Foss NIRSystem 6500 is one of the most commonly used laboratory instruments in agriculture and in particular in feed. New technological developments include micro-electro mechanical system (MEMS) technology, used in miniature handheld instruments such as the Polychromix Phazir spectrometer that are increasingly required for on-site analysis. The objective of this study was to assess the potential of a calibration transfer from the Foss NIRSystem 6500 to the Polychromix Phazir. The results show that good calibration models were obtained for various feed properties (fat, fiber, protein, and starch) developed on a Foss NIRSystem 6500, based on a spectral database of 9164 samples transferred to a Polychromix Phazir handheld spectrometer.
Classification of Raw and Roasted Semen Cassiae Samples with the Use of Fourier Transform Infrared Fingerprints and Least Squares Support Vector Machines
Authors: Lai Yanhua , Ni Yongnian , Kokot Serge
Published: October 2010

Raw and roasted Semen Cassiae seeds, a complex traditional Chinese medicine (TCM), are used as examples to research and develop a method of classification analysis based on measurements of Fourier transform infrared (FT-IR) spectral fingerprints. Eighty samples of the TCM were measured in the mid-infrared range, 400–2000 cm−1 (KBr pellets), and the complex overlapping spectra were submitted for interpretation to a principal component analysis least squares support vector machine (PC-LS-SVM), kernel principal component analysis least squares support vector machine (KPC-LS-SVM), and radial basis function artificial neural networks (RBF-ANN). The LS-SVM models were developed with an RBF kernel function and a grid search technique. Training models were constructed with the use of raw and first-derivative spectra and these were then verified by another data set containing both raw and roasted spectral objects. It was demonstrated that the first-derivative data set produced the best separation of the spectral objects. In general, satisfactory analytical performance was obtained with the PC-LS-SVM, KPC-LS-SVM, and RBF-ANN training models and with the classification of the verification spectral objects. With regard to chemometrics modeling, the performance of KPC-LS-SVM was somewhat more economical than that of the PC-LS-SVM model. It would appear that the latter relatively simple model would be sufficient for application to most small to medium sized FT-IR fingerprint data sets, but with larger matrices the more complex models, such as the RBF-ANN and KPC-LS-SVM, may be more advantageous on a computational basis.
A Study of Complex Formation between Polyacrylic Acid and Poly(Ethylene Oxide) by near Resonance Rayleigh Scattering
Authors: Li Yunbo , Li Haixia , Sun Yantao , Chen Xudong , Zhu Yubin
Published: October 2010

A series of near resonance Rayleigh scattering (NRRS) experiments has been performed on the phase behavior of complex formation between polyacrylic acid (PAA) and poly(ethylene oxide) (POE). On the basis of the theory of resonance scattering, as one new method compared to resonance Rayleigh scattering (RRS), NRRS was demonstrated to investigate polymer solutions. The results indicated that the complex formation induces an increase of the intensity of resonance scattering and the phase segregation leads to distortion of the resonance scattering spectrum with decreasing pH value. The collapse of macromolecular chains is attributed to the contraction of PAA chains and association between PAA and POE. Moreover, NRRS can show more information than RRS on the basis of their scattering spectra.
Study of Inorganic Particles, Fibers, and Asbestos Bodies by Variable Pressure Scanning Electron Microscopy with Annexed Energy Dispersive Spectroscopy and Micro-Raman Spectroscopy in Thin Sections of Lung and Pleural Plaque
Authors: Rinaudo Caterina , Croce Alessandro , Musa Maya , Fornero Elisa , Allegrina Mario , Trivero Paolo , Bellis Donata , Sferch Daniela , Toffalorio Francesca , Veronesi Giulia , Pelosi Giuseppe
Published: October 2010

In a previous work it has been demonstrated that micro-Raman spectroscopy is a technique able to recognize crystalline phases on untreated samples. In that case, inorganic particles and uncoated fibers from bronchoalveolar lavage (BAL) of a patient affected by pneumoconiosis were identified and characterized. In this work the technique is applied to asbestos bodies, that is, to coated fibers, and on crystallizations and fibrous phases observed in the plural plaque from patients affected by mesothelioma. From the Raman analysis the abundant fibrous material observed in the pleural area is talc, whereas rounded grains in the pleural tissue show the Raman spectrum of apatite, a calcium phosphate mineral particular to bones. In the pulmonary tissue many asbestos bodies, consisting of the incorporated fibers coated by iron-rich proteins, were observed. Under the 632.8 nm laser beam of the spectrometer, photo-crystallization of hematite in the iron-rich material forming the asbestos bodies can be proposed by the changes in the Raman spectra acquired during subsequent acquisitions. Nevertheless, the identification of the mineral phase constituting the incorporated fiber was possible by analyzing the Raman spectra; the results were confirmed by variable pressure scanning electron microscopy with annexed energy dispersive spectroscopy (VP-SEM-EDS) analyses.
Discerning Some Tylenol Brands Using Attenuated Total Reflection Fourier Transform Infrared Data and Multivariate Analysis Techniques
Authors: Msimanga Huggins Z. , Ollis Robert J.
Published: October 2010

Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were used to classify acetaminophen-containing medicines using their attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectra. Four formulations of Tylenol (Arthritis Pain Relief, Extra Strength Pain Relief, 8 Hour Pain Relief, and Extra Strength Pain Relief Rapid Release) along with 98% pure acetaminophen were selected for this study because of the similarity of their spectral features, with correlation coefficients ranging from 0.9857 to 0.9988. Before acquiring spectra for the predictor matrix, the effects on spectral precision with respect to sample particle size (determined by sieve size opening), force gauge of the ATR accessory, sample reloading, and between-tablet variation were examined. Spectra were baseline corrected and normalized to unity before multivariate analysis. Analysis of variance (ANOVA) was used to study spectral precision. The large particles (35 mesh) showed large variance between spectra, while fine particles (120 mesh) indicated good spectral precision based on the F-test. Force gauge setting did not significantly affect precision. Sample reloading using the fine particle size and a constant force gauge setting of 50 units also did not compromise precision. Based on these observations, data acquisition for the predictor matrix was carried out with the fine particles (sieve size opening of 120 mesh) at a constant force gauge setting of 50 units. After removing outliers, PCA successfully classified the five samples in the first and second components, accounting for 45.0% and 24.5% of the variances, respectively. The four-component PLS-DA model ( R2=0.925 and Q2=0.906) gave good test spectra predictions with an overall average of 0.961 ± 7.1% RSD versus the expected 1.0 prediction for the 20 test spectra used.
Visible and Infrared Imaging Spectroscopy of Picasso's Harlequin Musician: Mapping and Identification of Artist Materials in Situ
Authors: Delaney John K. , Zeibel Jason G. , Thoury Mathieu , Littleton Roy , Palmer Michael , Morales Kathryn M. , Rie E. René de la , Hoenigswald Ann
Published: October 2010

Reflection imaging spectroscopy is a useful technique to remotely identify and map minerals and vegetation. Here we report on the mapping and identification of artists' materials in paintings using this method. Visible and infrared image cubes of Picasso's Harlequin Musician are collected using two hyperspectral cameras and combined into a single cube having 260 bands (441 to 1680 nm) and processed using convex geometry algorithms. The resulting 18 spectral end members are identified by comparison with library spectra, fitting by nonlinear mixing, and using results from luminescence imaging spectroscopy. The results are compared with those from X-ray fluorescence spectrometry, polarized light microscopy, and scanning electron microscopy–energy dispersive spectrometry (SEM/EDS). This work shows the potential of reflection imaging spectroscopy, in particular if the shortwave infrared region is included along with information from luminescence imaging spectroscopy.
Predicting the Fatty Acid Composition of Milk: A Comparison of Two Fourier Transform Infrared Sampling Techniques
Authors: Afseth Nils Kristian , Martens Harald , Randby Åshild , Gidskehaug Lars , Narum Bjørg , Jørgensen Kjetil , Lien Sigbjørn , Kohler Achim
Published: October 2010

In the present study a novel approach for Fourier transform infrared (FT-IR) characterization of the fatty acid composition of milk based on dried film measurements has been presented and compared to a standard FT-IR approach based on liquid milk measurements. Two hundred and sixty-two (262) milk samples were obtained from a feeding experiment, and the samples were measured with FT-IR as dried films as well as liquid samples. Calibrations against the most abundant fatty acids, CLA (i.e., 18:2 cis-9, trans-11), 18:3 cis-9, cis-12, cis-15, and summed fatty acid parameters were obtained for both approaches. The estimation errors obtained in the dried film calibrations were overall lower than the corresponding liquid sample calibrations. Similar and good calibrations (i.e., R2 ranges from 0.82 to 0.94 (liquid samples) and from 0.88 to 0.97 (dried films)) for short-chain fatty acids (6:0–14:0), 18:1 cis-9, SAT, MUFA, and iodine value were obtained by both approaches. However, the dried film approach was the only approach for which feasible calibrations (i.e., R2 ranges from 0.78 to 0.93) were obtained for the major saturated fatty acids 16:0 and 18:0, the minor fatty acid features 4:0, CLA (i.e., 18:2 cis-9, trans-11), PUFA, and the summed 18:1 trans isomers. For the dried film approach, logical spectral features were found to dominate the respective fatty acid calibration models. The preconcentration step of the dried film approach could be expected to account for a major part of the prediction improvements going from predictions in liquid milk to predictions in dried films. The dried film approach has a significant potential for use in high-throughput applications in industrial environments and might also serve as a valuable supplement for determination of genetic and breeding factors within research communities.
New Method for Raman Investigation of the Orientation of Collagen Fibrils and Crystallites in the Haversian System of Bone
Authors: Falgayrac Guillaume , Facq Sébastien , Leroy Gérard , Cortet Bernard , Penel Guillaume
Published: October 2010

Knowledge of the organization of the components of bone is of primary importance in understanding how this tissue responds to stresses and provides a starting point for the design and development of biomaterials. Bone structure has been the subject of numerous studies. The mineralized fiber arrangement in cortical bone is either a twisted or orthogonal plywood structure. Both mineral models coexist in compact bone. Raman polarized spectroscopy offers definite advantages in the study of biological samples, enabling the simultaneous analysis of mineral and organic components and the determination of molecular orientation through the polarization properties of the Raman scattering. In this study, we used the Raman polarization approach to simultaneously investigate the orientation of collagen fibrils and apatite crystals in human cortical bone. Raman bands ratios were monitored as a function of sample orientation. Specific ratios were chosen—such as ν3 PO4/ν1 PO4, amide III (1271 cm−1)/amide III (1243 cm−1), and amide I/amide III (1243 cm−1)—due to their sensitivity to apatite-crystal and collagen-fibril orientation. Based on this original approach, spatial changes were monitored as a function of distance from the Haversian canal. The results revealed simultaneous tilting in intra-lamellar collagen-fibril and mineral crystal orientations. These results are consistent with a twisted plywood organization in the Haversian bone structure at the lamellar level. But at molecular level, the co-alignment of the collagen fibrils and the apatite crystal is observed in the innermost lamellae and becomes gradually less ordered as the distance from the Haversian canal increases. This work highlights the interest of Raman spectroscopy for the multiscale investigation of bone structure.
On the Use of Electrospray Ionization and Desorption Electrospray Ionization Mass Spectrometry for Bulk and Surface Polymer Analysis
Authors: Bonnaire Nicolas , Dannoux Adeline , Pernelle Christine , Amekraz Badia , Moulin Christophe
Published: October 2010

Electrospray ionization (ESI) and desorption electrospray ionization (DESI) mass spectrometry were for the first time compared to investigate degradation products resulting from radiolysis of polyurethane (PUR) irradiated using accelerated electrons. First, DESI optimization was performed to obtain the best results in terms of sensitivity for surface polymer analysis. Then, a comparison was performed between DESI-MS and ESI-MS characterization of the degradation products of irradiated PUR with different doses up to 10 MGy. Similar results were obtained despite a lower sensitivity of DESI. Finally, DESI results obtained by direct surface analysis of irradiated PUR films as a function of depth were compared to bulk analysis results obtained by ESI. This comparison shows that degradation products of PUR are very comparable at the surface or within the polymer, confirming the radio-oxidation homogeneity.
Monte Carlo Simulation of Fluorescence Spectra of Normal and Dysplastic Cervical Tissues for Optimizing Excitation/Receiving Arrangements
Authors: Chu Shou Chia , Chiang Huihua Kenny
Published: October 2010

Recent studies have demonstrated that the autofluorescence technique is a very promising tool for early-stage cancer diagnosis in various tissues. Many researchers have applied the autofluorescence technique through fiber-optic cables to excite tissues and collect the fluorescent emission signal from the tissues for discrimination analysis. In this study, we developed a Monte Carlo–light-induced autofluorescence (MCS LIAF) simulation model to optimize the oblique angle in the excitation optical fiber and the spatial arrangements in the receiving optical fiber. Our aim was to discriminate cervical tissues at different dysplastic stages. The model combined the structure of multi-layered tissues, tissue optical scattering and absorption parameters, tissue fluorophore concentration, the characteristic fluorescent spectrum of fluorophores, and the excitation and receiving arrangement of the optical fibers. The results show that the optimal oblique angle of the excitation optical fiber is between 0° and 45° and that the optimal receiving optical fiber is positioned 200 μm away from the origin. We also observed that changing the excitation angle is very useful in differentiating normal from cervical intraepithelial neoplasia (CIN) I or CIN II tissues. Also, using the fluorescence peak ratio of NADH/collagen can help discriminate CIN III from normal tissues and CIN I/II tissues.
Qualitative and Quantitative Analysis of CO2 and CH4 Dissolved in Water and Seawater Using Laser Raman Spectroscopy
Authors: White Sheri N.
Published: October 2010

Laboratory experiments have been performed using laser Raman spectroscopy to analyze carbon dioxide (CO2) and methane (CH4) dissolved in water and seawater. Dissolved CO2 is characterized by bands at ∼1275 and 1382 Δcm−1. Dissolved CH4 is characterized by a dominant band at ∼2911 Δcm−1. The laboratory instrumentation used for this work is equivalent to the sea-going Raman instrument, DORISS (Deep Ocean Raman In Situ Spectrometer). Limits of quantification and calibration curves were determined for each species. The limits of quantification are ∼10 mM for CO2 and ∼4 mM for CH4. A ratio technique is used to obtain quantitative information from Raman spectra: the gas bands are referenced to the O–H stretching band of water. The calibration curves relating band height ratios to gas concentration are linear and valid for a range of temperatures, pressures, and salinities. Current instrumentation is capable of measuring the highest dissolved gas concentration observed in end-member hydrothermal fluids. Further development work is needed to improve sensitivity and optimize operational configurations.
Electronic State Distributions of YBa2Cu3O7-x Laser-Ablated Plumes
Authors: Kee Patrick D. , Perram Glen P.
Published: October 2010

A systematic study of the spectrally resolved atomic emission arising from the laser ablation of YBa2Cu3O7-x targets in the presence of an oxygen background reveals statistically distributed populations with characteristic temporally averaged electronic temperatures of 0.28–0.38 eV, 0.28–0.37 eV, and 0.40–0.48 eV for neutral barium, yttrium, and copper, respectively. The higher electronic temperatures of the lighter copper atoms cannot be explained by the effects of temporal averaging, as the time-of-flight spectra are similar for all three atomic species. The electronic temperatures decline slowly with distance from the target, with a characteristic length of 20 to 200 mean free paths. The plume kinetic energies determined from gated imagery recorded time-of-flight spectra are much higher, 3–250 eV, suggesting a small fraction of the kinetic energy is converted to electronic excitation during each collision at the shock contact front. A correlation between electronic temperatures and shock strength reduces the dimensionality of the dependence on pressure and target distance. The dependence of electronic temperature on deposition condition is weak, suggesting the electronic state distribution is a poor candidate as a monitor for process control during the manufacture of coated conductors.
Scattering Correction by Use of a Priori Information
Authors: Ottestad Silje , Isaksson Tomas , Saeys Wouter , Wold Jens Petter
Published: October 2010

In this paper we demonstrate how a limited amount of a priori knowledge about spectral variability can be used in extended multiplicative scattering correction (EMSC) to remove disturbing effects such as light scattering variation in visible and near-infrared spectra prior to data modeling. Two different datasets were studied. In the first dataset, pigment concentrations (astaxanthin) were estimated in a model system with different concentrations of the scattering agent intralipid. Different cases were created by including varying levels of intralipid in the calibration set and then applying the models on sample sets with scattering properties both within and outside the calibration range. Including the most accurate estimate of light scattering in the EMSC model gave root mean square errors of prediction (RMSEP) that were similar to a cross-validated global model including all samples, even for extreme extrapolation with regard to scattering properties. Less accurate estimates gave on average RMSEPs half of what could be achieved using EMSC without any a priori knowledge, suggesting that the method also has potential in cases where the accurate light scattering spectrum is difficult to obtain. In the second dataset carbohydrate concentrations (sucrose, fructose, and glucose) were estimated in orange-juice mixtures where unwanted spectral variation was caused by a change in distance between transmittance fiber-optic probes. This caused two different interfering phenomena due to path length variation and saturation in the detection system. The prediction results for a model based on spectra collected at one specific probe distance treated with EMSC with a correction spectrum were comparable to what could be achieved by a global model including spectra collected at three different distances. The corresponding RMSEPs for models using EMSC with no correction term were in the worst cases 4, 22, and 36 times higher for sucrose, fructose, and glucose, respectively.
Photophysics Associated with Site Selectively Templated and Tagged Xerogel Sensor Platforms
Authors: Holthoff Ellen L. , Bright Frank V.
Published: October 2010

The analytical signal produced from a site selectively templated and tagged xerogel (SSTTX) based sensor is more completely elucidated. In an SSTTX, target analyte (TA) binding sites are created within a xerogel and a fluorescent reporter molecule (e.g., nitrobenzo-2-oxa-1,3-diazole, NBD) is covalently and selectively positioned within the template site. TA binding modulates the NBD cybotactic region, yielding a TA concentration-dependent change in the NBD reporter fluorescence. Our results reveal that there are two NBD sub-populations within the SSTTX. One sub-population is associated with misformed template sites that bind TA poorly and the NBD reporter molecules are heavily quenched by an adjacent amine residue that is intentionally positioned within close proximity to the NBD reporter molecule. The second NBD sub-population is associated with a properly formed template site that binds TA; the adjacent amine is still present but it is not as close to the NBD in comparison to the misformed site. When TA is present, the TA-responsive site binds TA, the TA disrupts the adjacent amine–NBD interaction (dequenching), and the NBD fluorescence increases. All NBD quenching occurs via photo-induced electron transfer (PET) from the adjacent amines to the excited NBD reporter molecules. As the mole fraction ratio of n-octyltrimethoxysilane (C8-TMOS) to tetramethoxysilane (TMOS) within an SSTTX increases, the misformed site mole fraction decreases and the dissociation constant ( Kd) for TA binding to the TA-responsive site decreases by 13-fold.
On the Use of Overtone and Combination Bands for the Analysis of the CaSO4—H2O System by Mid-Infrared Reflection Spectroscopy
Authors: Rosi Francesca , Daveri Alessia , Doherty Brenda , Nazzareni Sabrina , Brunetti Brunetto G. , Sgamellotti Antonio , Miliani Costanza
Published: October 2010

With the aim of characterizing ground preparations of paintings by infrared reflection spectroscopy, the CaSO4–H2O system (gypsum/bassanite/anhydrite) has been re-investigated, evaluating and assigning the SO42- and OH overtone and combination bands, respectively, in the ranges 1900–2700 cm−1 and 5000–6000 cm−1 resulting from reflection and high concentration transmission spectra. The second-order modes have been proven to be highly specific, reliable, and less affected by overlap with bands of organic binders and can hence be exploited for the identification of the sulfate hydration phase using infrared (IR) reflection spectroscopy. Subsequently, the characterization and identification of hydration phases in unknown sulfate-based ground preparations on authentic artworks have been carried out noninvasively by fiber-optic reflection IR spectroscopy and on cross-sections by infrared reflection micro-spectroscopy. The spectroscopic data collected both on standards and artworks have been cross-validated by X-ray diffraction.
Ultraviolet—Visible Absorption and Luminescence Properties of Quinacridone—Barium Sulfate Solid Mixtures
Authors: Gentili Pier Luigi , Clementi Catia , Romani Aldo
Published: October 2010

The absorption and emission spectral features of the dye quinacridone (QA) have been studied in solution and in the solid phase. In the solid phase, QA has been investigated as pure microcrystalline powder and mixed with barium sulfate (BaSO4) in different mass percentages. Two kinds of QA–BaSO4 mixtures have been prepared: physical blends of the two microcrystalline powders, and mixtures with gum arabic as binder. The latter was used in painting mock-ups. Luminescence properties of the mixtures have been investigated using both steady-state and time-resolved techniques. The prepared samples have allowed the Kubelka–Munk correction model, formulated for the emission spectra, to be tested. Moreover, the luminescence decay profiles have been analyzed using the maximum entropy method (MEM) and the nonlinear least-squares method. All the results obtained highlight how physical (self-absorption) and chemical (composition of the microenvironment) factors can influence the spectral and kinetic properties of dyes. These factors should always be taken into account in the diagnostic activity applied to works of art.
Fluorescence Instrument Response Standards in Two-Photon Time-Resolved Spectroscopy
Authors: Luchowski Rafal , Szabelski Mariusz , Sarkar Pabak , Apicella Elisa , Midde Krishna , Raut Sangram , Borejdo Julian , Gryczynski Zygmunt , Gryczynski Ignacy
Published: October 2010

We studied the fluorescence properties of several potential picosecond lifetime standards suitable for two-photon excitation from a Ti:sapphire femtosecond laser. The fluorescence emission of the selected fluorophores (rose bengal, pyridine 1, and LDS 798) covered the visible to near-infrared wavelength range from 550 to 850 nm. We suggest that these compounds can be used to measure the appropriate instrument response functions needed for accurate deconvolution of fluorescence lifetime data. Lifetime measurements with multiphoton excitation that use scatterers as a reference may fail to properly resolve fluorescence intensity decays. This is because of the different sensitivities of photodetectors in different spectral regions. Also, detectors often lose sensitivity in the near-infrared region. We demonstrate that the proposed references allow a proper reconvolution of measured lifetimes. We believe that picosecond lifetime standards for two-photon excitation will find broad applications in multiphoton spectroscopy and in fluorescence lifetime imaging microscopy (FLIM).
A Prototype Hand-Held Raman Sensor for the in situ Characterization of Meat Quality
Authors: Schmidt Heinar , Sowoidnich Kay , Kronfeldt Heinz-Detlef
Published: October 2010

As a tool for the in situ characterization of meat quality, a hand-held Raman sensor head using an excitation wavelength of 671 nm was developed. A microsystem-based external cavity diode laser module was integrated into the sensor head and attached to a Raman probe, which is equipped with lens optics for excitation and signal collection as well as a Raman filter stage for Rayleigh rejection. The Raman signal was guided by an optical fiber to the detection unit, which was in the initial phase a laboratory spectrometer with a charge-coupled device (CCD) detector. The laser and the sensor head were characterized in terms of stability and performance for in situ Raman investigations. Raman spectra of meat were obtained with 35 mW within 5 seconds or less, ensuring short measuring times for the hand-held device. In a series of measurements with raw and packaged pork meat, the Raman sensor head was shown to detect microbial spoilage on the meat surface, even through the packaging foil.
Complexation of Europium(III) with the Zwitterionic Form of Amino Acids Studied with Ultraviolet—Visible and Time-Resolved Laser-Induced Fluorescence Spectroscopy
Authors: Heller Anne , Rönitz Olivia , Barkleit Astrid , Bernhard Gert , Ackermann Jörg-Uwe
Published: October 2010

The complex formation of europium(III) with the zwitterionic form of amino acids (alanine, phenylalanine, and threonine) has been studied in aqueous solution. Measurements were performed at I = 0.1 M (NaCl/NaClO4), room temperature, and trace metal concentrations in the range of pH 2 to 8 using ultraviolet–visible (UV-Vis) and time-resolved laser-induced fluorescence spectroscopy (TRLFS). While complexation leads to a significant luminescence enhancement in the emission spectrum of the metal ion, absorption in the UV-Vis spectrum of the amino acid (AA) decreases. As zwitterionic species (AAH), all three ligands form weak complexes with 1:1 stoichiometry and a general formula of EuAAH3+ with the metal. The complex stability constants were determined to be log K ∼ 1 for all complexes, indicating the negligible contribution of the amino acid side chain to the complex formation reaction.
Effective Suppression of Stray Light in Rotational Coherent Anti-Stokes Raman Spectroscopy Using an Angle-Tuned Short-Wave-Pass Filter
Authors: Bohlin Alexis , Bengtsson Per-Erik
Published: October 2010

Stray light interference is a common problem in spontaneous rotational Raman spectroscopy and rotational coherent anti-Stokes Raman spectropscopy (CARS). The reason is that the detected spectrum appears in the spectral vicinity of the probe beam wavelength, and stray light at this wavelength from optics and surfaces is hard to suppress. In this Note, efficient suppression of stray light is demonstrated for rotational CARS measurements using a commercially available short-wave-pass filter. By angle-tuning this filter with a specified cut-off wavelength at 561 nm, the cut-off wavelength could be tuned to a desired spectral position so that more than 80% transmission is achieved as close as 15 cm−1 (∼0.4 nm) from the probe beam wavelength of 532.0 nm, while the intensity at this wavelength is suppressed by two orders of magnitude.
Fluorescent and Ultraviolet—Visible Spectroscopy Studies on the Antioxidation and DNA Binding Properties of Binuclear Tb(III) Complexes
Authors: Liu Yongchun , Jiang Xinhui , Yang Zhengyin , Zheng Xudong , Liu Jianning , Zhou Tianlin
Published: October 2010

Tb(III) complexes were prepared from Tb(NO3)3·6H2O and four Schiffbase ligands derived from 8-hydroxyquinoline-2-carboxaldehyde with aroylhydrazines. X-ray crystal and other structural analyses indicate that Tb(III) and every ligand can form a binuclear Tb(III) complex with 1:1 metal-to-ligand stoichiometry and nine-coordination at the Tb(III) center. Viscosity titration experiments and fluorescent and ultraviolet-visible (UV-Vis) spectroscopy results indicate that all the Tb(III) complexes can bind to Calf thymus DNA through intercalation with the binding constants at the order of magnitude of 106–107 M__1, and they may be used as potential anticancer drugs, but complexes containing active phenolic hydroxy groups may have stronger antitumor activities. Antioxidation results indicate that all the Tb(III) complexes have strong abilities of scavenging hydroxyl radicals and superoxide radicals, but complexes containing active phenolic hydroxy groups show stronger scavenging effects on hydroxyl radicals and complexes containing N-heteroaromatic substituent show stronger scavenging effects on superoxide radicals. However, Tb(III) emission with these systems is not observed, for these ligands rather are quenchers and unable to sensitize this metal ion.
The Unique Molecular Behavior of Water at the Chloroform—Water Interface
Authors: McFearin Cathryn L. , Richmond Geraldine L.
Published: October 2010

The molecular bonding and orientation of water at the chloroform–water interface has been examined in this study using vibrational sum-frequency spectroscopy (VSFS). The results provide a key puzzle piece towards our understanding of the systematic changes in the interfacial bonding and orientation of water that occur with variations in the polarity of the organic phase, especially when compared with previous studies of different liquid–liquid interfacial systems. In these VSFS studies the OH spectral responses of interfacial water molecules are used to characterize the interactions between water and the organic phase. The spectral analysis, aided by isotopic dilution studies, shows that the moderate polarity of the chloroform phase results in a mixed interfacial region with stronger organic–water bonding and fewer bonding interactions between adjacent water molecules than was previously found for studies of non-polar organic liquid–water interfaces. Even with the more mixed interfacial region and stronger organic–water interactions, interfacial water retains a significant amount of orientational ordering. These results are compared with recent predictions from molecular dynamics simulations about how molecules behave at the chloroform–water interface.