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Intense Bands (intense + bands)
Selected AbstractsRaman spectroscopic study of the magnesium-carbonate minerals,artinite and dypingiteJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2009Ray L. Frost Abstract Magnesium minerals are important in the understanding of the concept of geosequestration. The two hydrated hydroxy magnesium-carbonate minerals artinite and dypingite were studied by Raman spectroscopy. Intense bands are observed at 1092 cm,1 for artinite and at 1120 cm,1 for dypingite, attributed ,1 symmetric stretching mode of CO32,. The ,3 antisymmetric stretching vibrations of CO32, are extremely weak and are observed at 1412 and 1465 cm,1 for artinite and at 1366, 1447 and 1524 cm,1 for dypingite. Very weak Raman bands at 790 cm,1 for artinite and 800 cm,1 for dypingite are assigned to the CO32,,2 out-of-plane bend. The Raman band at 700 cm,1 of artinite and at 725 and 760 cm,1 of dypingite are ascribed to CO32,,2 in-plane bending mode. The Raman spectrum of artinite in the OH stretching region is characterised by two sets of bands: (1) an intense band at 3593 cm,1 assigned to the MgOH stretching vibrations and (2) the broad profile of overlapping bands at 3030 and 3229 cm,1 attributed to water stretching vibrations. X-ray diffraction studies show that the minerals are disordered. This is reflected in the difficulty of obtaining Raman spectra of reasonable quality, and explains why the Raman spectra of these minerals have not been previously or sufficiently described. Copyright © 2008 John Wiley & Sons, Ltd. [source] Laser-induced phase changes in olivine FePO4: a warning on characterizing LiFePO4 -based cathodes with Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2009Christopher M. Burba Abstract Raman spectroscopy is an excellent technique for probing lithium intercalation reactions of many diverse lithium ion battery electrode materials. The technique is especially useful for probing LiFePO4 -based cathodes because the intramolecular vibrational modes of the PO43, anions yield intense bands in the Raman spectrum, which are sensitive to the presence of Li+ ions. However, the high power lasers typically used in Raman spectroscopy can induce phase transitions in solid-state materials. These phase transitions may appear as changes in the spectroscopic data and could lead to erroneous conclusions concerning the delithiation mechanism of LiFePO4. Therefore, we examine the effect of exposing olivine FePO4 to a range of power settings of a 532-nm laser. Laser power settings higher than 1.3 W/mm2 are sufficient to destroy the FePO4 crystal structure and result in the formation of disordered FePO4. After the laser is turned off, the amorphous FePO4 compound crystallizes in the electrochemically inactive ,-FePO4 phase. The present experimental results strongly suggest that the power setting of the excitation laser should be carefully controlled when using Raman spectroscopy to characterize fundamental lithium ion intercalation processes of olivine materials. In addition, Raman spectra of the amorphous intermediate might provide insight into the ,-FePO4 to olivine FePO4 phase transition that is known to occur at temperatures higher than 450 °C. Copyright © 2008 John Wiley & Sons, Ltd. [source] Raman spectroscopy of three polymorphs of BiVO4: clinobisvanite, dreyerite and pucherite, with comparisons to (VO4)3 -bearing minerals: namibite, pottsite and schumacheriteJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2006Ray L. Frost Abstract Both Raman and infrared spectroscopy have been used to characterise the three phase-related minerals,dreyerite (tetragonal BiVO4), pucherite (orthorhombic BiVO4) and clinobisvanite (monoclinic BiVO4),and a comparison of the spectra is made with that of the minerals namibite (Cu(BiO2)VO4(OH)), schumacherite (Bi3O(OH)(VO4)2) and pottsite (PbBiH(VO4)2·2H2O). Pucherite, clinobisvanite and namibite are characterised by VO4 stretching vibrations at 872, 824 and 846 cm,1. The Raman spectrum of dreyerite shows complexity in the 750 to 950 cm,1 region with two intense bands at 836 and 790 cm,1 assigned to the symmetric and antisymmetric VO4 modes. The minerals schumacherite and pottsite are characterised by bands at 846 and 874 cm,1. In both the infrared and Raman, spectra bands are observed in the 1000,1100 cm,1 region which are attributed to the antisymmetric stretching modes. The Raman spectra of the low wavenumber region are complex. Bands are identified in the 328 to 370 cm,1 region and in the 404 to 498 cm,1 region and are assigned to the ,2 and ,4 bending modes. The minerals namibite and schumacherite are characterised by intense bands at 3514 and 3589 cm,1 assigned to the symmetric stretching vibrations of the OH units. Importantly, Raman spectroscopy enables new insights into the chemistry of these bismuth vanadate minerals. Raman spectroscopy enables the identification of the bismuth vanadate minerals in mineral matrices where paragenetic relationships exist between the minerals. Copyright © 2006 John Wiley & Sons, Ltd. [source] IgE reactivity to latex allergens among sensitized healthcare workers before and after immunotherapy with latexALLERGY, Issue 2 2006J. Sastre Background:, New IgE sensitizations to proteins in allergen extracts have been shown to occur during allergen-specific immunotherapy (IT). Methods:, Twenty-four healthcare workers (HCWs) , patients included in a latex IT study , were analysed, 16 in active treatment and eight in placebo. Sera were obtained at baseline and after 6 months of IT and analysed with immunoblotting and CAP System with eight single recombinant latex allergens (rHev b 1, 3, 5, 6.01, 8, 9, 10, 11, and a mix of rHev b1, 5, 6.01 and 8). Results:, After IT with latex, three patients in the active treatment group had new IgE sensitizations, one to Hev b 5, one to Hev b 11 and another to Hev b 6.01. No other significant variation in mean of specific IgE to latex or recombinant allergens were observed in patients who received placebo or active treatment. A significant (P = 0.012) negative correlation (,0.72) was observed between maximal tolerated dose and specific IgE to Hev b 6.01 at baseline. After IT, immunoblot analysis demonstrated a significant increase in IgE binding in a band of approximately 22 kDa (P = 0.032) that may correspond to Hev b 6.01. New or more intense bands appeared in seven patients of the active group, while in three subjects a reduction was observed. Conclusions:, Hev b 6.01 seems to be the most relevant latex allergen in HCWs. New or more intense IgE binding to latex allergenic components occurs during latex immunotherapy. However, the levels of specific IgE against these new components are low and do not seem to have clinical relevance. [source] Investigation of bacterial communities associated with asymptomatic and symptomatic endodontic infections by denaturing gradient gel electrophoresis fingerprinting approachMOLECULAR ORAL MICROBIOLOGY, Issue 6 2004J. F. Siqueira Jr The purpose of the present study was to investigate the bacterial communities associated with asymptomatic and symptomatic endodontic infections and to compare denaturing gradient gel electrophoresis (DGGE) fingerprinting patterns of these two clinical conditions. The root canal microbiota of teeth associated with asymptomatic or symptomatic periradicular lesions was profiled by the PCR-DGGE method and then compared, taking into consideration the banding patterns. Bacteria were present in all examined cases. Comparative analysis of the two clinical conditions revealed bands that were common to both symptomatic and asymptomatic cases, but most DGGE bands appeared to be unique for each clinical condition. No single band occurred in all profiles. The mean number of bands detected in the 16S rDNA community profiles were 12.1 ± 9.4 (range 2,29) for symptomatic samples and 6.7 ± 2.7 (range 2,11) for asymptomatic ones. Clustering methods and principal component analysis of DGGE banding pattern placed the samples according to the presence or absence of symptoms. Four intense bands that were excised from the gel and sequenced showed similarities to species of the Campylobacter genus (found in 5/12 asymptomatic and in 3/11 symptomatic cases), Fusobacterium genus (4/11 symptomatic cases), Acinetobacter genus (5/12 asymptomatic cases), and Enterobacteriaceae family (11/12 asymptomatic and 2/11 symptomatic cases). The profiles of the predominant bacterial community appeared to be unique for each individual. These findings confirm that endodontic infections are polymicrobial and showed that there are significant differences in the predominant bacterial composition between asymptomatic and symptomatic cases. [source] | ||||||||||