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Studied Material (studied + material)
Selected AbstractsConoscopic method for determination of main refractive indices and thickness of a uniaxial crystal cut out parallel to its optical axisJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2009Leonas Dumitrascu This paper presents a simplified data acquisition and analysis technique for use in determining the main refractive indices and thickness of a uniaxial anisotropic layer cut out parallel to the optical axis, by processing the conoscopic interference figures obtained using a polarizing microscope equipped with a CCD camera. For negative uniaxial crystals, the equations used permit the calculation of the optical sign of the studied material so it is not necessary to insert a quartz wedge into the conoscopic beam. The technique can also be applied to the study of liquid crystal layers in a planar orientation. [source] Contribution to X-ray analysis of carbo-nitrided steel layersJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2001J. M. Sprauel The non-destructive X-ray diffraction method is used to analyse carbo-nitrided steel layers after wear testing. These measurements are carried out on the two major phases of the material, i.e. the martensite and the retained austenite. Such measurements are particularly difficult for three reasons. First, strong gradients exist across the wear track. Second, the diffraction peaks obtained for the martensite are broadened, as a result of the overlap of different reflections of the tetragonal structure. Third, the studied material is multiphase. Its major phases are martensite and austenite, but it also contains carbide and nitride clusters, which lead to incoherent scattering of X-rays. A new quantitative phase analysis method is thus proposed to define the volume fractions of these different constituents of the material. This method accounts for the evolution of the background level during wear. A micro-mechanical model is then developed to process the diffraction peak positions obtained for the martensite and the retained austenite. This model defines the `true' stress and carbon content of both phases. It also allows separation of the reflections of the martensite. The true widths of the diffraction peaks, which characterize the plastic deformation, can thus be quantified. Results for wear-test specimens show a strong plastic deformation of the retained austenite during contact fatigue. This leads to a partial transformation of this phase into martensite. In the martensite, on the contrary, the plastic deformation remains low but the carbon content decreases. This is caused by a stress-induced precipitation of carbides. [source] Structural study of NaNO2 embedded into porous glassPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007E. Rysiakiewicz-Pasek Abstract Temperature-dependent Raman study of NaNO2 confined within porous glass with a pore size of 46 nm has been performed. It is demonstrated that the bandwidths and frequencies of the Raman bands as a function of temperature show similar behaviour, but not identical, as those observed for bulk NaNO2. This result indicates that the first-order phase transition mechanism is only slightly modified by embedding NaNO2 into the porous glass. It seems that formation of "premelted state" is not significant in the studied material, at least up to 40-50 K above Tc. At higher temperatures, however, a significant increase of bandwidth of the 1326 cm,1 band is observed, which could indicate appearance of "premelted" state. The dielectric measurements are consistent with this view since they show large increase of dielectric permittivity above 480 K, well below the NaNO2 melting temperature (554 K). (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ability of different restorative materials to prevent in situ secondary caries: analysis by polarized light-microscopy and energy-dispersive X-rayEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2008Thaís Cachuté Paradella Secondary caries is the main cause of direct restoration replacement. The purpose of this study was to analyze enamel adjacent to different restorative materials after in situ cariogenic challenge using polarized-light microscopy (PLM), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDS). Twelve volunteers, with a low level of dental plaque, a low level of mutans streptococci, and normal salivary flow, wore removable palatal acrylic appliances containing enamel specimens restored with Z250 composite, Freedom composite, Fuji IX glass-ionomer cement, or Vitremer resin-modified glass-ionomer for 14 days. Volunteers dripped one drop of 20% sucrose solution (n = 10) or distilled water (control group) onto each specimen 8 times per day. Specimens were removed from the appliances and submitted to PLM for examination of the lesion area (in mm2), followed by dehydration, gold-sputtering, and submission to SEM and EDS. The calcium (Ca) and phosphorus (P) contents were evaluated in weight per cent (%wt). Differences were found between Z250 and Vitremer, and between Z250 and FujiIX, when analyzed using PLM. Energy-dispersive X-ray analysis results showed differences between the studied materials regarding Ca %wt. In conclusion, enamel adjacent to glass-ionomer cement presented a higher Ca %wt, but this material did not completely prevent enamel secondary caries under in situ cariogenic challenge. [source] Radiopacity of root filling materials using digital radiographyINTERNATIONAL ENDODONTIC JOURNAL, Issue 7 2007J. R. Carvalho-Junior Abstract Aim, To evaluate radiopacity of root filling materials using digital radiography. Methodology, The sealers tested were AH PlusTM, Endofill®, EndoREZTM and EpiphanyTM. Gutta-percha (Dentsply Maillefer) and ResilonTM cones were also tested. Acrylic plates, containing six wells, measuring 1 mm in depth and 5 mm in diameter, were prepared for the test, and filled with the materials. The test samples were radiographed together with an aluminium stepwedge calibrated in millimetres, according to ANSI/ADA Specification 57. For the radiographic exposures, digital imaging plates and an X-ray machine at 70 kVp and 8 mA were used. The object-to-focus distance was 30 cm, and the exposure time, 0.2 s. After the laser optic reading process, the software determined the radiopacity of the standardized areas, using grey-scale values, calculating the average radiographic density for each material. Results, The decreasing values of radiopacity of the studied materials, expressed in millimetres of aluminium equivalent, were: ResilonTM (13.0), AH PlusTM (11.2), gutta-percha (9.8), EpiphanyTM (8.0), Endofill® (6.9) and EndoREZTM (6.6). Conclusion, All materials had radiopacity values above 3 mm of aluminium recommended by ANSI/ADA Specification 57. [source] Dehydration studies using a novel multichamber microscale fluid bed dryer with in-line near-infrared measurementJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2003Eetu Räsänen Abstract The purpose of this research was to study the effect of two process parameters (temperature and moisture content) on dehydration behavior of different materials using a novel multichamber microscale fluid bed dryer with a process air control unit and in-line near-infrared (NIR) spectroscopy. The materials studied were disodium hydrogen phosphates with three different levels of hydrate water and wet theophylline granules. Measured process parameters of fluid bed drying were logged, including in-line NIR signals. Off-line analyses consisted of X-ray powder diffraction patterns, Fourier transform NIR spectra and moisture contents of studied materials. During fluid bed drying, the stepwise dehydration of materials was observed by the water content difference of inlet and outlet air, the pressure difference over the bed, and the in-line NIR spectroscopy. The off-line analysis confirmed the state of solid materials. The temperature and the moisture content of the process air were demonstrated to be significant factors for the solid-state stability of theophylline. The presented setup is a material and cost-saving approach for studying the influence of different process parameters on dehydration behavior during pharmaceutical processing. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:2074,2081, 2003 [source] | |||||||||||||