Hybrid hard- and soft-modelling applied to analyze ultrafast processes by femtosecond transient absorption spectroscopy: study of the photochromism of salicylidene anilines.

Multivariate curve resolution-alternating least squares (MCR-ALS) of multi-experiment data analysis was successfully applied to elucidate the photodynamics of the N-(3-methylsalicylidene)-3-methylaniline by analyzing UV-vis femtosecond transient absorption spectra. The two-way data obtained present some specific difficulties linked to the nature of the transient spectra collected and to the overlapping of the photodynamics of the solvent and other contributions at short time scale (below 1 ps). Advantage was taken from the flexibility of the hybrid hard-soft multivariate curve resolution (HS-MCR) approach to consider a non-absorbing contribution in the kinetic model and to provide a functional description of the solvent in soft-modelling.

Chemometrics description of measurement error structure: study of an ultrafast absorption spectroscopy experiment.

The error structure inherent to a transient absorption spectroscopy kinetic experiment is described through the examination of the related measurement error covariance matrices in the time and the spectral direction. The systematic approach proposed by Wentzell's group to characterize the measurement error covariance matrices is used for this purpose. The goals of this study are identifying and modelling the factors contributing to the error measurement and proposing a weighting error-based scheme that can be generally used when analysing data coming from this experimental setup.

Monitoring and interpretation of photoinduced biochemical processes by rapid-scan FTIR difference spectroscopy and hybrid hard and soft modeling.

Natural photochemical processes often require special instrumentation to monitor them at a suitable time scale. Rapid-scan FTIR difference spectroscopy is one of the preferred techniques to obtain rich structural information in the scale of milliseconds about photochemical processes of complex natural systems. The difference spectra obtained by this technique enhance the fine spectroscopic changes undergone during the process but require powerful data analysis methodologies to take full advantage of the information provided.

Contribution made by multivariate curve resolution applied to gel permeation chromatography-Fourier transform infrared data for an in-depth characterization of styrene-butadiene rubber blends.

We evaluate the contribution made by multivariate curve resolution-alternating least squares (MCR-ALS) for resolving gel permeation chromatography-Fourier transform infrared (GPC-FT-IR) data collected on butadiene rubber (BR) and styrene butadiene rubber (SBR) blends in order to access in-depth knowledge of polymers along the molecular weight distribution (MWD). In the BR-SBR case, individual polymers differ in chemical composition but share almost the same MWD. Principal component analysis (PCA) gives a general overview of the data structure and attests to the feasibility of modeling blends as a binary system.

Super-resolution and Raman chemical imaging: from multiple low resolution images to a high resolution image.

Imaging in Raman spectroscopy is a valuable tool for analytical chemistry. Although molecular characterization at micron level is achieved for many applications, it usually fails producing chemical images of micron size samples as expected in chemical, environmental and biological analysis. The aim of the work is to introduce the potential of super-resolution in vibrational spectroscopic imaging.

The benzophenone S1(n,pi*) --> T1(n,pi*) states intersystem crossing reinvestigated by ultrafast absorption spectroscopy and multivariate curve resolution.

The well-known benzophenone intersystem crossing from S(1)(n,pi*) to T(1)(n,pi*) states, for which direct transition is forbidden by El-Sayed rules, is reinvestigated by subpicosecond time-resolved absorption spectroscopy and effective data analysis for various excitation wavelengths and solvents. Multivariate curve resolution alternating least-squares analysis is used to perform bilinear decomposition of the time-resolved spectra into pure spectra of overlapping transient species and their associated time-dependent concentrations. The results suggest the implication of an intermediate (IS) in the relaxation process of the S(1) state.

Genetic algorithm optimisation combined with partial least squares regression and mutual information variable selection procedures in near-infrared quantitative analysis of cotton-viscose textiles.

In this work, different approaches for variable selection are studied in the context of near-infrared (NIR) multivariate calibration of textile. First, a model-based regression method is proposed. It consists in genetic algorithm optimisation combined with partial least squares regression (GA-PLS).

Multivariate curve resolution of rapid-scan FTIR difference spectra of quinone photoreduction in bacterial photosynthetic membranes.

Photosynthetic reaction centres and membranes are systems of particular interest and are often taken as models to investigate the molecular mechanisms of selected bioenergetic reactions. In this work, a multivariate curve resolution by alternating least squares procedure is detailed for resolution of time-resolved difference FTIR spectra probing the evolution of quinone reduction in photosynthetic membranes from Rhodobacter sphaeroides under photoexcitation. For this purpose, different data sets were acquired in the same time range and spectroscopic domain under slightly different experimental conditions.

Quantitative analysis of cotton-polyester textile blends from near-infrared spectra.

Quantitative analysis of textile blends and textile fabrics is currently of particular interest in the industrial context. In this frame, this work investigates whether the use of Fourier transform (FT) near-infrared (NIR) spectroscopy and chemometrics is powerful for rapid and accurate quantitative analysis of cotton-polyester content in blend products. As samples of the same composition have many sources of variability that affect NIR spectra, indirect prediction is particularly challenging and a large sample population is required to design robust calibration models.

Quality evaluation of sugar beet (Beta vulgaris) by near-infrared spectroscopy.

The legal method (polarimetric measurement) for the determination of sucrose content and the wet chemical analysis for the quality control of sugar beet uses lead acetate. Because heavy metals are pollutants, the law could forbid their use in the future. Therefore, near-infrared spectroscopy (NIRS) was evaluated as a procedure to replace these methods.

Multivariate curve resolution methods in imaging spectroscopy: influence of extraction methods and instrumental perturbations.

Imaging spectroscopy is becoming a key field of analytical chemistry. In the face of more and more complex samples, we actually need accurate microscopic insight. Nowadays, the methods used to produce concentration maps of the pure compounds from spectral data sets are based on the classical univariate approach although multivariate approaches are sometimes investigated.

Time-resolved step-scan FT-IR spectroscopy: focus on multivariate curve resolution.

The present paper describes the application of step-scan FT-IR spectroscopy in combination with chemometric analysis of the spectral data for the study of the photocycle of bacteriorhodopsin. The focus is on the performance of this instrumentation for time-resolved experiments. Three-dimensional data-spectra recorded over time-are studied using various factor analysis techniques, e.

The secondary structure and architecture of human elastin.

The presented work constitutes the first structural characterization of both insoluble human elastin and its solubilized form, kappa-elastin. Structural data were reached following the use of Fourier transform infrared, near infrared Fourier transform Raman and circular dichroism optical spectroscopic methods and their quantitative analysis permitted us to estimate approximately 10% alpha-helices, approximately 35% beta-strands and approximately 55% undefined conformations in the global secondary structure of insoluble human elastin in the solid state. Following the use of the LINK method, the probable local distribution of the secondary-structure elements along the sequence was determined and compared to that obtained for bovine elastin, the historical standard of elastin.

FT-IR and X-ray spectroscopic investigations of Na-diclofenac-cyclodextrins interactions.

The association of DCF-Na (the salt of the 2-[(2,6-dichlorophenyl)amino]-phenyl-acetic acid) with beta-CD (cyclodextrin) in some therapeutic formulas can contribute to the optimisation of the physico-chemical and pharmaceutical properties of the parent drug. The understanding of the interaction between DCF with beta-CD represents the objective of this study. FT-IR spectroscopy is one of the methods which clarify the nature of these interactions in complexes of such type.

Infrared and Raman microspectrometry study of fluor-fluor-hydroxy and hydroxy-apatite powders.

Visible Raman and infrared microspectrometry studies performed on fluorapatite and hydroxyapatite powders have shown similar results. Small modifications of the nu2 and nu4 PO(3-)4 tetrahedra bending modes are observed. A small frequency shift of the nu1 mode and modifications on the nu3 mode region accompanied with a simplification of the hydroxyapatite and fluorapatite respective spectra from seven to four bands were observed.

Bovine elastin and kappa-elastin secondary structure determination by optical spectroscopies.

Elastin is the macromolecular polymer of tropoelastin molecules responsible for the elastic properties of tissues. The understanding of its specific elasticity is uncertain because its structure is still unknown. Here, we report the first experimental quantitative determination of bovine elastin secondary structures as well as those of its corresponding soluble kappa-elastin.

[HPLC used in the validation of simple methods for research of degradation products in essential drug tablets].

HPLC have been used to validate simple methods to be employed in developing countries (DC) for the quality control of drugs. As the important lack of analytical material in DC, colorimetric methods have been used. These are subjected to visual appreciation of the color intensity.

[Non-destructive quality control of tablets by photoacoustic infrared spectrometry. Analysis in primary packaging].

We have studied the feasibility of the photoacoustic detection in Fourier transform infrared spectrometry for the quality control of drug tablets. Beyond the non destructive character of the method, the main advantage which has been established is the precocity of impurity detection on the tablet outside. The direct recording of spectra through PVC lead to interesting results for study of tablets under blister.

XeCl laser in biliary calculus fragmentation: fluence threshold and ablation products.

The in vitro action of a xenon-chlorine (XeCl) excimer laser on biliary calculi is reported: fluence threshold and rate for ablation process are given. An analysis of gaseous products evolved during irradiation of gallstones, performed through an infrared spectrophotometric technique is also reported. Based on the different results, we discuss the mechanism of destruction.

Gas chromatography with Fourier transform infrared spectrometry for biomedical applications.

The basic concepts relating to Fourier transform infrared spectroscopy (FTIR) have been set out to enable chromatographers to make use of gas chromatography (GC)-FTIR coupling. To describe the current position regarding applications, studies are briefly presented that are representative of the field of industrial products, natural vegetable extracts and pesticides. Biomedical applications are described in detail.

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To increase the analytical potential of the combination of gas chromatography and Fourier-transform infrared spectrometry, we have adapted our system to use of capillary columns, and automated the acquisition and treatment of the data. The performance of the method was tested by analysis of complex mixtures such as the essential oils of peppermint and lavender. The sensitivity and resolution are poorer than those obtained with classical GC detectors but the spectra are very useful for determining molecular structure.

[Drug addiction by inhalation of gasoline vapor. Clinical and toxicological aspects].

Following an epidemic of sniffing petrol fumes and the death of a child, the authors review published findings of this little-known type of toxicomania. They envisage the Clinical and Toxicological problems. Researching and identifying the petrol remain problems.