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Reflection Mode (reflection + mode)
Selected AbstractsDrug release phenomena within a hydrophobic starch acetate matrix: FTIR mapping of tablets after in vitro dissolution testingJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2008Jari Pajander Abstract The aim of this study was to assess the utility of Fourier transform infrared mapping to study the drug release phenomena within a hydrophobic matrix tablet. Starch acetate with a degree of substitution (2.7) was used as a hydrophobic matrix former. Anhydrous caffeine and riboflavin sodium phosphate were used as water soluble model drugs. The USP (XXVIII) paddle-method was selected as an in vitro dissolution test. Mapping of the diluted tablets' cross-section was performed by attenuated total reflection mode. Fourier transform infrared mapping can distinguish drug particles from the bulk matrix and it can be considered as a valuable method for obtaining both quantitative and qualitative information on drug release processes. The physicochemical properties of the drug compound strongly contribute to its release behavior when the USP paddle in vitro dissolution test is used. Mapping of the riboflavin product revealed a more homogenous matrix distribution due to its smaller particle size. Consequently, its dissolution release profile was more uniform than caffeine which possessed a wider particle size distribution and lower solubility. Mapping showed that caffeine became localized in the lower part of the tablet unlike riboflavin. The hydrodynamic conditions during the in vitro release test might contribute to this differentiation. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97: 3367,3378, 2008 [source] New thermosets obtained by the cationic copolymerization of diglycidyl ether of bisphenol A with ,-caprolactone with an improvement in the shrinkage.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2007Abstract Diglycidyl ether of bisphenol A was cured with different proportions of ,-caprolactone with ytterbium triflate as an initiator. The curing was studied by means of differential scanning calorimetry and Fourier transform infrared in the attenuated total reflection mode. The latter was used to monitor the competitive reactive processes and to quantify the conversions of the epoxide, lactone, and intermediate spiroorthoester groups. A partial depolymerization process from the cured material to free ,-caprolactone was also identified. The formation of a stable carbocation and the coordinative capability of ytterbium triflate were the reasons for this unexpected process. The thermal and dynamic mechanical properties of the cured materials were determined with differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. An increase in the proportion of ,-caprolactone resulted in an increased curing rate, a decrease in the shrinkage after gelation, and a significant decrease in the glass transition temperature. The introduction of ester linkages into the three-dimensional structure led to more thermally degradable thermosets. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1968,1979, 2007 [source] Frequency selective surface with dual band switchable reflection and transmission characteristicsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2009A. Munir Abstract A pin diode-loaded active doubly periodic flat strip FSS is shown to act as a dynamic screen. It is shown that by means of d.c. bias control, we can utilize the screen in, (1) transmission mode as a dual band electromagnetic shutter, or with the inclusion of a ground plane in reflection mode, as (2) a dual band refection canceller, (3) an amplitude shift keying (ASK) spatial modulator. The properties of the FSS are characterized using a specially designed parallel plate waveguide simulator that permits normal incidence excitation of the FSS under test. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2059,2061, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24547 [source] Spectroscopic phase modulated ellipsometry in application to some novel single and polycrystalline ternary compoundsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2006N. Mamedov Abstract The results of the application of the spectroscopic phase modulated ellipsometry (SPME) to a series of novel ternary compounds from anisotropic to polycrystalline are presented to show the high effectiveness of this optical technique with regard to the dielectric function of the new materials. Besides, SPME in specular reflection mode to study the polarization degree of the light reflected at specular angle is shown to be very informative in determination of the best conditions for optical measurements on rough surfaces such as, for example, surfaces of the polycrystalline ternary thiogallate compounds studied in this work. An incoherent approach relating the measured depolarization with the surface variance and optical constants of a material or thin film is proposed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Three-dimensional fiber orientation in vibration welded joints of glass fiber reinforced polyamide-6POLYMER COMPOSITES, Issue 9 2008Musa R. Kamal A technique was developed to obtain the three-dimensional distribution of fiber orientation in vibration-welded joints of polyamide-6 (PA-6) reinforced with 30 wt% glass fibers. The heat-affected zone (HAZ) of fiber-reinforced PA-6 was successfully revealed by polishing and etching the vibration welded joints. Examination with the polarized light microscope in the reflection mode showed detailed microstructure domains, including the bulk crystalline zone and the HAZ. Experimental elliptical fiber cross-section images were used to obtain second order orientation tensors, thus providing a quantitative description of the three-dimensional fiber orientation distribution. The fibers in the HAZ were reoriented towards the squeeze flow direction, when compared with the bulk phase. Low welding pressure does not necessarily produce a more favorable fiber orientation in the tensile direction than high welding pressure. High welding pressure and low amplitude promote fiber reorientation in both the squeeze flow and tensile (weld thickness) directions. Overall, it was found that, at 30% fiber content, vibration-welded joints of injection molded fiber-reinforced PA-6 are weaker than vibration-welded joints in unreinforced injection molded samples. The fibers in the former do not undergo sufficient reorientation to influence weld strength in the tensile direction. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] An in situ method for the study of strain broadening using synchrotron X-ray diffractionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2007C. C. Tang A tensonometer for stretching metal foils has been constructed for the study of strain broadening in X-ray diffraction line profiles. This device, which is designed for use on powder diffractometers and was tested on Station 2.3 at Daresbury Laboratory, allows in situ measurements to be performed on samples under stress. It can be used for data collection in either transmission or reflection modes using either symmetric or asymmetric diffraction geometries. As a test case, measurements were carried out on an 18,µm-thick copper foil experiencing strain levels of up to 5% using both symmetric reflection and symmetric transmission diffraction. All the diffraction profiles displayed peak broadening and asymmetry which increased with strain. The measured profiles were analysed by the fundamental-parameters approach using the TOPAS peak-fitting software. All the observed broadened profiles were modelled by convoluting a refineable diffraction profile, representing the dislocation and crystallite size broadening, with a fixed instrumental profile predetermined using high-quality LaB6 reference powder. The deconvolution process yielded `pure' sample integral breadths and asymmetry results which displayed a strong dependence on applied strain and increased almost linearly with applied strain. Assuming crystallite size broadening in combination with dislocation broadening arising from f.c.c. a/2,110,{111} dislocations, the variation of mechanical property with strain has been extracted. The observation of both peak asymmetry and broadening has been interpreted as a manifestation of a cellular structure with cell walls and cell interiors possessing high and low dislocation densities. [source] | |||||||||||||