Search results for "Spectral"
showing 10 items of 3116 documents
Conjugation reactions of polyaromatic quinones to mono- and bisglutathionyl adducts: Direct analysis by fast atom bombardment mass spectrometry
1988
The conjugation products of several reactive quinones with glutathione have been identified by fast atom bombardment mass spectrometry. Appropriate conditions have been developed which enabled the direct, dynamic mass spectral analysis of spontaneous, as well as glutathione transferase catalysed conjugation reactions. Applications to a series of quinones provided the direct detection and differentiation of the formation of mono- and bisglutathionyl adducts between regioisomeric quinone substrates in that only 1,4-quinones yielded bisglutathionyl adducts, which were not observed for the 1,2-isomers.
Characterization of commercial synthetic resins by pyrolysis-gas chromatography/mass spectrometry: application to modern art and conservation.
2009
To characterize a set of synthetic resins, a methodology by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) has been developed. The studied reference materials were commercial versions of a wide range of synthetic resins. For each polymer, the pyrolytic and chromatographic conditions were optimized to adequately resolve the fragment mixture in a short time. The proposed analytical method does not require previous treatment of the sample, and due to its high sensitivity, only a small sample quantity in the microgram range can be used. The pyrolysis temperature was found to have little effect on the obtained pyrograms. The summarized data set for the individual polymer materials, es…
Underdamped soft phonon in orthorhombic BaTiO3
1990
Abstract Raman scattering measurements are reported in orthorhombic phase and through the orthorhombic-rhombohedral transition of BaTiO3. Spectra reveal the presence of an underdamped low frequency phonon which slightly softens with decreasing temperature and abruptly stiffens at the transition to the rhombohedral phase. Results are discussed in comparison with isomorphous KNbO3 and tetragonal BaTiO3 and are interpreted as due to a dominant displacive mechanism.
Dynamics of cross polarization in solid state nuclear magnetic resonance experiments of amorphous and heterogeneous natural organic substances
2008
Nuclear magnetic resonance (NMR) experiments on carbon-13 in the solid state were done with cross polarization (CP) and magic angle spinning (MAS) in order to overcome the low NMR sensitivity of (13)C and the chemical shift anisotropy, respectively. In the present research, CPMAS (13)C-NMR spectra were collected by modulating the contact time needed for cross polarization (variable contact times experiments, VCT) on two different humic acids (a soil-HA and a coal-HA). VCT data were fitted by a model containing either a monotonic or a non-monotonic cross polarization term. The non-monotonic model, which fitted the experimental results better than the monotonic one, provided two cross-polariz…
Synthesis and characterization of the acetazolamide complexes of Co(II) and Zn(II)
1987
Abstract The preparation and characterization of the complexes of Acetazolamide (Acm) with Co(II) and Zn(II) are described. The complexes are of the type M(Acm) 2 (NH 3 ) 2 . Monodentate or bidentate behaviour of Acm from the electronic properties and the IR spectral data is discussed. The probable structures of the complexes are proposed.
The transformation of aromatic molecules into the subspace of their double bonds
1975
A model of new submolecules is presented. As an application some absorptions of aromatic radicals are interpreted in UV and visible spectra. Extension of the model to biological systems is prejudged.
<title>Iodine and mercury resonance lamps and their spectrum in far UV</title>
2001
Electrodeless iodine, mercury iodide, and mercury radio- frequency discharge lamps have been made to provide effective sources of atomic spectra for analytical spectroscopy providing powerful resonance radiation of iodine and mercury in the 120-253 nm region. The lamps are required and can be used for spectral calibration, resonance absorption, and fluorescence detection techniques, for investigation of atomic characteristics (e.g., branching ratios) and other purposes where intense monochromatic spectra are needed. Production technology, development, and investigation of the UV and VUV emission are described.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downlo…
13C NMR spectra of eudesmanolides I—eudesman-12,6-olides
1987
The 13C NMR spectra of 26 eudesmanolides of natural and synthetic origin have been measured, including the naturally occurring sesquiterpene lactones artemisin, torrentin, rothin-A and rothin-B and several semi-synthetic eudesman-12,6-olides obtained from artemisin. The chemical shift values of the different compounds are compared and the effects of the substituents are discussed.
Sesquiterpene lactones from iranian Artemisia species
1993
Abstract The aerial parts of Artemisia turcomanica and A. deserti yielded two new germacranolides, a new guaianolide, and several known mono- and sesquiterpenes.
Dunham coefficients of 14N2 from CARS measurements of high vibrational states in a low-pressure discharge
1988
Spectroscopic constants of the X1Σg+ ground state of 14N2 are deduced from CARS spectra recorded in a 4 Torr d.c. N2 glow discharge. Vibrational states up to ν = 14 have been observed but only the 11 lower levels which have a good signal-to-noise ratio have been processed. The Dunham constants that were deduced yield vibrational band centre positions in good agreement with those of Lofthus and Krupenie.