Search

Fulgurites are naturally occurring structures that are formed when lightning discharges reach the ground. In this investigation, the mineralogical compositions of core and shell compartments of a rare, iron-rich fulgurite from the Mongolian Gobi Desert were investigated by X-ray diffraction and micro-Raman spectroscopy. The interpretation of the Raman data was helped by chemometric analysis, using both multivariate curve resolution (MCR) and principal component analysis (PCA), which allowed for the fast identification of the minerals present in each region of the fulgurite. In the core of the fulgurite, quartz, microcline, albite, hematite, and barite were first identified based on the Raman spectroscopy and chemometrics analyses. In contrast, in the shell compartment of the fulgurite, the detected minerals were quartz, a mixture of the K-feldspars orthoclase and microcline, albite, hematite, and goethite. The Raman spectroscopy results were confirmed by X-ray diffraction analysis of powdered samples of the two fulgurite regions, and are consistent with infrared spectroscopy data, being also in agreement with the petrographic analysis of the fulgurite, including scanning electron microscopy with backscattering electrons (SEM-BSE) and scanning electron microscopy with energy dispersive X-ray (SEM-EDX) data. The observed differences in the mineralogical composition of the core and shell regions of the studied fulgurite can be explained by taking into account the effects of both the diffusion of the melted material to the periphery of the fulgurite following the lightning and the faster cooling at the external shell region, together with the differential properties of the various minerals. The heavier materials diffused slower, leading to the concentration in the core of the fulgurite of the iron and barium containing minerals, hematite, and barite. They first underwent subsequent partial transformation into goethite due to meteoric water within the shell of the fulgurite. The faster cooling of the shell region kinetically trapped orthoclase, while the slower cooling in the core area allowed for the extensive formation of microcline, a lower temperature polymorph of orthoclase, thus justifying the prevalence of microcline in the core and a mixture of the two polymorphs in the shell. The total amount of the K-feldspars decreases only slightly in the shell, while quartz and albite appeared in somewhat larger amounts in this compartment of the fulgurite. On the other hand, at the surface of the fulgurite, barite could not be stabilized due to sulfate lost (in the form of SO2 plus O-2 gaseous products). The conjugation of the performed Raman spectroscopy experiments with the chemometrics analysis (PCA and, in particular, MCR analyses) was shown to allow for the fast identification of the minerals present in the two compartments (shell and core) of the sample. This way, the XRD experiments could be done while knowing in advance the minerals that were present in the samples, strongly facilitating the data analysis, which for compositionally complex samples, such as that studied in the present investigation, would have been very much challenging, if possible. Scientific Research Unit of Istanbul Kultur University-IKU BAP Project Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) Portuguese Foundation for Science and Technology

The molecular structures and vibrational spectra of the three isomers of pyridinecarboxamide (picolinamide, nicotinamide, isonicotinamide) were calculated with the Density Functional Theory (DFT) method using the B3LYP function and the 6-31++G(d,p), Z2PolX, Z3PolX basis sets. The calculations were performed by using the Gaussian98W packet program set. The total energy distributions (TED) of the vibrational modes of these molecules were calculated by using the Scale 2.0 program and the vibrational modes of the molecules were determined. The Scaled Quantum Mechanical (SQM) method was used in the scaling procedure. In the experimental part of the study, the solid phase FT-IR and Micro Raman spectra of the three isomers of pyridinecarboxamide have been recorded in the range of 4000–650 and 1200–100 cm −1 , respectively. The calculated wavenumbers were compared to the corresponding experimental values. As a result, the observed bands of the three isomers of pyridinecarboxamide were assigned with good accuracy.

Prothionamide (PTH) is the secondary drug used against Mycobacterium tuberculosis bacteria and leprosy. The aim of this work was to investigate the potential energy surface map, anharmonic and harmonic vibrational spectra, NBO analysis and ELF (Electron Localization Function) of the title compound using DFT approach with the B3LYP (Becke, three-parameter, Lee–Yang–Parr) exchange–correlation functional with the 6-31G++(d, p) and the Z3POLX basis sets were employed. In the experimental part of this study, FT-Mid IR, FT-Far IR and FT-Raman spectra of the molecule were recorded in the regions 4000–450 cm −1 , 700–30 cm −1 and 4000–100 cm −1 respectively in the solid phase. The comparison between calculated and experimental vibrational spectra (infrared and Raman spectra) and assignments of fundamental vibrational modes were characterized by total energy distribution (TED). Theoretical spectra were seen to be in good agreement with those of the experimental ones.

The FT-IR and FT-Raman spectra of isonicotinamide (in solid phase) have been recorded in the regions 4000–400 and 4000–70 cm −1 , respectively. The geometry optimizations and vibrational spectrum calculations of isonicotinamide have been carried out at the DFT/B3LYP level with 6-31++G(d,p) basis set. With the SQM approach, the force field of isonicotinamide obtained by DFT calculations has been corrected by a set of scaling factors to get a good agreement between observed and calculated wavenumbers. Isonicotinamide interacting with Al(OH) 3 has also been studied by B3LYP/6-31++G(d,p) calculations and the SQM results of both molecules have been compared to investigate how the coordination through the ring nitrogen effects the isonicotinamide vibrational wavenumbers.

The vibrational wavenumbers of kyotorphin [ l -Tyr 1 – d -Arg 2 ] analogue ( d -KTP) was determined by using theoretical and experimental methods. The optimised structure of kyotorphin was obtained on the basis of parameter set determined for l -tyrosine and d -arginine molecules. After then the vibrational wavenumbers of kyotorphin were calculated by density functional theory (DFT) approximation, using the B3LYP function with 6-31G(d,p) basis set. The vibrational assignment was given by the help of total energy distribution (TED) of the vibrational modes of the d -KTP. The characteristic Fermi doubled of tyrosine was observed at 853 and 828 cm −1 in the Raman spectrum of d -KTP and the intensity ratio ( I 853 / I 828 ) was found to be 1.6, indicating that both phenoxyl proton and oxygen are involved in H-bonding interaction in d -KTP.

In this study, a methodology based on Fourier-transform infrared spectroscopy and principal component analysis and partial least square methods is proposed for the analysis of blood plasma samples in order to identify spectral changes correlated with some biomarkers associated with schizophrenia and bipolarity. Our main goal was to use the spectral information for the calibration of statistical models to discriminate and classify blood plasma samples belonging to bipolar and schizophrenic patients. IR spectra of 30 samples of blood plasma obtained from each, bipolar and schizophrenic patients and healthy control group were collected. The results obtained from principal component analysis (PCA) show a clear discrimination between the bipolar (BP), schizophrenic (SZ) and control group' (CG) blood samples that also give possibility to identify three main regions that show the major differences correlated with both mental disorders (biomarkers). Furthermore, a model for the classification of the blood samples was calibrated using partial least square discriminant analysis (PLS-DA), allowing the correct classification of BP, SZ and CG samples. The results obtained applying this methodology suggest that it can be used as a complimentary diagnostic tool for the detection and discrimination of these mental diseases. (C) 2015 Elsevier B.V. All rights reserved.

Molecular structure of 2-[4-(4-Fluorobenzamido)phenyl]benzothiazole was determined by quantum chemical calculations. MidIR and FarIR spectra were recorded at room temperature, with 4 cm−1 resolution in the 4000–400 cm−1 and 700–30 cm−1 regions, respectively for the first time. Raman spectrum was recorded in the 4000–100 cm−1 range. Optimized molecular structure and vibrational wavenumbers of the compound in its ground state have been calculated by using Density Functional Theory using B3LYP functional with 6-311++G(d,p) basis set. Vibrational wavenumbers were seen to be in good agreement with the experimental IR data. Furthermore, assignments of each vibrational mode were interpreted in terms of potential energy distributions in detail.