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Peak Profiles (peak + profile)
Selected AbstractsSpontaneous Current Oscillations during Hard Anodization of Aluminum under Potentiostatic ConditionsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Woo Lee Abstract Nanoporous anodic aluminum oxide is prepared by hard anodization of aluminum under potentiostatic conditions using 0.3,M H2C2O4. Under unstirred electrolyte condition, spontaneous current oscillations are observed. The amplitude and period of these current oscillations are observed to increase with anodization time. As a consequence of the oscillatory behavior, the resulting anodic alumina exhibits modulated pore structures, in which the diameter contrast and the length of pore modulation increase with the amplitude and the period of current oscillations, respectively, and the current peak profile determines the internal geometry of oxide nanopores. The mechanism responsible for the oscillatory behavior is suggested to be a diffusion-controlled anodic oxidation of aluminum. [source] All optical multi-tap microwave filter with high sidelobe suppression using peak profile of ASE and one multiwavelength FBGMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2009Li Xia Abstract A new all optical 10-tap microwave filter is proposed using a broadband amplified spontaneous emission (ASE) light source and a single specially designed multiwavelength FBG. Measured results show that the sidelobe suppression is larger than 20 dB. The filter response is insensitive to the polarization state of light. This technique enables one to obtain a simple and low cost photonic microwave filter with a stable response. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2522,2524, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24666 [source] Variable-Temperature Powder X-ray Diffraction of Aromatic Carboxylic Acid and Carboxamide CocrystalsCHEMISTRY - AN ASIAN JOURNAL, Issue 4 2007L. Sreenivas Reddy Abstract The effect of temperature on the cocrystallization of benzoic acid (BA), pentafluorobenzoic acid (FBA), benzamide (BAm), and pentafluorobenzamide (FBAm) is examined in the solid state. BA and FBA formed a 1:1 complex 1 at ambient temperature by grinding with a mortar and pestle. Grinding FBA and BAm together resulted in partial conversion into the 1:1 adduct 2 at 28,°C and complete transformation into the product cocrystal at 78,°C. Further heating (80,100,°C) and then cooling to room temperature gave a different powder pattern from that of 2. BAm and FBAm hardly reacted at ambient temperature, but they afforded the 1:1 cocrystal 3 by melt cocrystallization at 110,115,°C. Both BA+FBAm (4) and BA+BAm (5) reacted to give new crystalline phases upon heating, but the structures of these products could not be determined owing to a lack of diffraction-quality single crystals. The stronger COOH and CONH2 hydrogen-bonding groups of FBA and FBAm yielded the equimolar cocrystal 6 at room temperature, and heating of these solids to 90,100,°C gave a new crystalline phase. The X-ray crystal structures of 1, 2, 3, and 6 are sustained by the acid,acid/amide,amide homosynthons or acid,amide heterosynthon, with additional stabilization from phenyl,perfluorophenyl stacking in 1 and 3. The temperature required for complete transformation into the cocrystal was monitored by in,situ variable-temperature powder X-ray diffraction (VT-PXRD), and formation of the cocrystal was confirmed by matching the experimental peak profile with the simulated diffraction pattern. The reactivity of H-bonding groups and the temperature for cocrystallization are in good agreement with the donor and acceptor strengths of the COOH and CONH2 groups. It was necessary to determine the exact temperature range for quantitative cocrystallization in each case because excessive heating caused undesirable phase transitions. [source] Symmetrization of diffraction peak profiles measured with a high-resolution synchrotron X-ray powder diffractometerJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2006H. Hibino The asymmetry of diffraction peak profiles observed with a high-resolution synchrotron powder X-ray diffractometer has been successfully removed by a double deconvolution method. In the first step, the asymmetry caused by the axial divergence aberration of the diffractometer is removed by a whole-pattern deconvolution method based on an a priori theoretical model for the aberration. In the second step, the residual asymmetry, the origin of which can be ascribed to the aberrations of the beamline optics, is also removed by a whole-pattern deconvolution method, based on an empirical model derived from the analysis of experimental diffraction peak profiles of a standard Si powder (NIST SRM640b). The beamline aberration has been modelled by the convolution of a pseudo-Voigt or Voigt function with an exponential distribution function. It has been found that the angular dependence of the asymmetry parameter in the exponential function is almost proportional to tan,, which supports the idea that the residual asymmetry should be ascribed mainly to the intrinsic asymmetry in the spectroscopic distribution of the source X-ray supplied by the beamline optics of the synchrotron facility. Recently developed procedures of whole-pattern deconvolution have been improved to treat the singularity of the instrumental function in the measured angular range. Formulae for the whole-pattern deconvolution based on the Williamson,Hall-type dependence of the width parameter of the instrumental function have also been developed. The method was applied to the diffraction intensity data of a standard ZnO powder sample (NIST SRM674) measured with a high-resolution powder diffractometer on beamline BL4B2 at the Photon Factory. The structure parameters of ZnO were refined from the integrated peak intensities, which were extracted by an individual profile fitting method applying symmetric profile models. The refined structure parameters coincide fairly well with those obtained from single-crystal data. [source] Limitations of asymmetric parallel-beam geometryJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2004N. A. Raftery Bragg diffraction peak profiles and intensities in asymmetric (,,2,) diffraction using a mirror-based parallel-beam geometry were compared with symmetric parallel-beam (,,2,) and conventional Bragg,Brentano (,,2,) diffraction for a powdered quartz sample and the NIST standard reference material (SRM) 660a (LaB6, lanthanum hexaboride). A comparison of the intensities and line widths (full width at half-maximum, FWHM) of these techniques demonstrated that low incident angles (,,<,5°) are preferable for the parallel-beam setup. For higher , values, if 2,,<,2,, mass absorption reduces the intensities significantly compared with the Bragg,Brentano setup. The diffraction peak shapes for the mirror geometry are more asymmetric and have larger FWHM values than corresponding peaks recorded with a Bragg,Brentano geometry. An asymmetric mirror-based parallel-beam geometry offers some advantages in respect of intensity when compared with symmetric geometries, and hence may be well suited to quantitative studies, such as those involving Rietveld analysis. A trial Rietveld refinement of a 50% quartz,50% corundum mixture was performed and produced adequate results. [source] Diffraction peak profiles from spherical crystallites with lognormal size distributionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2003T. Ida An efficient and accurate method to evaluate the theoretical diffraction peak profiles from spherical crystallites with lognormal size distribution (SLN profile) is presented. Precise results can be obtained typically by an eight-term numerical integral for any values of the parameters, by applying an appropriate substitution of the variable to the integral formula. The calculated SLN profiles have been verified by comparison with those calculated by inverse Fourier transform from the exact analytical solution of the Fourier-transformed SLN profile. It has been found that the shape of the SLN profile strongly depends on the variance of size distribution. When the logarithmic standard deviation , of the size distribution is close to 0.76, the SLN profile becomes close to a Lorentzian profile, and `super-Lorentzian' profiles are predicted for larger values of ,, as has been concluded by Popa & Balzar [J. Appl. Cryst. (2002), 35, 338,346]. The intrinsic diffraction peak profiles of an SiC powder sample obtained by deconvolution of the instrumental function have certainly shown `super-Lorentzian' line profiles, and they are well reproduced by the SLN profile for the value , = 0.93. [source] Deconvolution of instrumental aberrations for synchrotron powder X-ray diffractometryJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2003T. Ida A method to remove the effects of instrumental aberrations from the whole powder diffraction pattern measured with a high-resolution synchrotron powder diffractometer is presented. Two types of asymmetry in the peak profiles caused by (i) the axial-divergence aberration of the diffractometer (diffractometer aberration) and (ii) the aberration of the monochromator and focusing optics on the beamline (beamline aberration) are both taken into account. The method is based on the whole-pattern deconvolution by Fourier technique combined with the abscissa-scale transformation appropriate for each instrumental aberration. The experimental powder diffraction data of LaB6 (NIST SRM660) measured on beamline BL-4B2 at the Photon Factory in Tsukuba have been analysed by the method. The formula of the scale transformation for the diffractometer aberration has a priori been derived from the instrumental function with geometric parameters of the optics. The strongly deformed experimental peak profiles at low diffraction angles have been transformed to sharp peak profiles with less asymmetry by the deconvolution of the diffractometer aberration. The peak profiles obtained by the deconvolution of the diffractometer aberration were modelled by an asymmetric model profile function synthesized by the convolution of the extended pseudo-Voigt function and an asymmetric component function with an empirical asymmetry parameter, which were linearly dependent on the diffraction angle. Fairly symmetric peak profiles have been obtained by further deconvolution of the empirically determined asymmetric component of the beamline aberration. [source] Automated profile analysis for single-crystal diffraction dataJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2003R. J. Angel An integration method for step-scanned single-crystal intensity data based upon fitting of the individual diffraction profiles by a pseudo-Voigt function is presented. Algorithms for both the recovery of weak intensities from data sets and the rejection of aberrant peak profiles are discussed. The ideas presented in this paper have been implemented in a software package for Microsoft Windows, WinIntegrStp, which is available at http://www.crystal.vt.edu/. [source] A new method for analysing peak broadening caused by compositional fluctuation in X-ray diffraction measurementsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2001Kiichi Nakashima A new method for analysing X-ray peak broadening caused by compositional fluctuation is proposed. The method is applicable to epitaxial layers with diamond or zinc-blende structure on (001) substrates. In the new method, a rescaling procedure with a difference variable ,A is applied to measured X-ray profiles and the dependence of the profiles on various reflection indices hkl is analysed. The theoretical formula reveals that X-ray peak profiles become independent of hkl after the rescaling. A new criterion is proposed; an experimental examination based on the criterion makes it possible simply to judge whether or not X-ray peak broadening is caused by compositional fluctuation. The method is verified experimentally and demonstrated by applying it to an InGaAs multilayer sample having artificial compositional fluctuation. [source] Refinement of modulated structures against X-ray powder diffraction data with JANA2000JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2001M. Du JANA is a computer program for the refinement and analysis of periodic and aperiodic (incommensurately modulated structures and composite crystals) crystal structures. Here a new module is introduced that allows Rietveld refinements against powder diffraction data. It is shown that JANA2000 provides a state-of-the-art description of the peak profiles. A re-analysis of the low-temperature structure of (CO)xC60 showed that the application of icosahedral symmetry restrictions to the C60 molecule leads to a better description of the electron density and to a corrected position of the CO molecule as compared with a rigid-body refinement. The incommensurately modulated structure of NbTe4 has been successfully refined against X-ray powder diffraction data. The structural parameters are equal to, but less accurate, than the parameters obtained from a single-crystal study. [source] Rietveld analysis of X-ray powder diffraction patterns as a potential tool for the identification of impact-deformed carbonate rocksMETEORITICS & PLANETARY SCIENCE, Issue 11 2009Sarah A. Huson Entire XRD patterns, single peak profiles and Rietveld refined parameters of carbonate samples from the Sierra Madera impact crater, west Texas, unshocked equivalent samples from 95 miles north of the crater and the Mission Canyon Formation of southwest Montana and western Wyoming were used to evaluate the use of X-ray powder diffraction as a potential tool for distinguishing impact deformed rocks from unshocked and tectonically deformed rocks. At Sierra Madera dolostone and limestone samples were collected from the crater rim (lower shock intensity) and the central uplift (higher shock intensity). Unshocked equivalent dolostone samples were collected from well cores drilled outside of the impact crater. Carbonate rocks of the Mission Canyon Formation were sampled along a transect across the tectonic front of the Sevier and Laramide orogenic belts. Whereas calcite subjected to significant shock intensities at the Sierra Madera impact crater can be differentiated from tectonically deformed calcite from the Mission Canyon Formation using Rietveld refined peak profiles, weakly shocked calcite from the crater rim appears to be indistinguishable from the tectonically deformed calcite. In contrast, Rietveld analysis readily distinguishes shocked Sierra Madera dolomite from unshocked equivalent dolostone samples from outside the crater and tectonically deformed Mission Canyon Formation dolomite. [source] Characterization of QoI resistance in Botrytis cinerea and identification of two types of mitochondrial cytochrome b genePLANT PATHOLOGY, Issue 1 2009S. Banno Botrytis cinerea field isolates collected in Japan were screened for resistance to Qo inhibitor fungicides (QoIs). Of the 198 isolates screened, six grew well on a medium containing azoxystrobin, a QoI, when salicylhydroxamic acid, an alternative oxidase inhibitor, was present. The resistance mutation in the cytochrome b gene (cytb) was characterized. All QoI-resistant isolates had the same mutation (GGT to GCT) in cytb that led to the substitution of glycine by alanine at position 143 of cytochrome b, which is known to confer QoI resistance in plant pathogens. To detect this mutation, a hybridization probe assay based on real-time PCR amplification and melting curve analysis was developed. Using DNA samples prepared from aubergines coinfected with QoI-resistant and QoI-sensitive B. cinerea isolates, two similar peak profiles with their corresponding melting temperatures were obtained. This result suggests that QoI-resistant and QoI-sensitive isolates may compete equally in terms of pathogenicity, and the assay may be used to assess the population ratio of mutant and wild-type isolates. However, the hybridization probe did not anneal to PCR products derived from the DNA samples of some QoI-sensitive isolates. Structural analysis of cytb revealed that B. cinerea field isolates could be classified into two groups: one with three introns and the other with an additional intron (Bcbi-143/144 intron) inserted between the 143rd and 144th codons. All 88 isolates possessing the Bcbi-143/144 intron were azoxystrobin-sensitive, suggesting that the QoI-resistant mutation at codon 143 in cytb prevents self-splicing of the Bcbi-143/144 intron, as proposed in some other plant pathogens. [source] Strategy for the elucidation of elemental compositions of trace analytes based on a mass resolution of 100 000 full width at half maximumRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2010Anton Kaufmann Elemental compositions (ECs) can be elucidated by evaluating the high-resolution mass spectra of unknown or suspected unfragmented analyte ions. Classical approaches utilize the exact mass of the monoisotopic peak (M,+,0) and the relative abundance of isotope peaks (M,+,1 and M,+,2). The availability of high-resolution instruments like the Orbitrap currently permits mass resolutions up to 100 000 full width at half maximum. This not only allows the determination of relative isotopic abundances (RIAs), but also the extraction of other diagnostic information from the spectra, such as fully resolved signals originating from 34S isotopes and fully or partially resolved signals related to 15N isotopes (isotopic fine structure). Fully and partially resolved peaks can be evaluated by visual inspection of the measured peak profiles. This approach is shown to be capable of correctly discarding many of the EC candidates which were proposed by commercial EC calculating algorithms. Using this intuitive strategy significantly extends the upper mass range for the successful elucidation of ECs. Copyright © 2010 John Wiley & Sons, Ltd. [source] A simple pharmacokinetics subroutine for modeling double peak phenomenonBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 3 2006Ahmad Mirfazaelian Abstract Double peak absorption has been described with several orally administered drugs. Numerous reasons have been implicated in causing the double peak. DRUG-KNT,a pharmacokinetic software developed previously for fitting one and two compartment kinetics using the iterative curve stripping method,was modified and a revised subroutine was incorporated to solve double-peak models. This subroutine considers the double peak as two hypothetical doses administered with a time gap. The fitting capability of the presented model was verified using four sets of data showing double peak profiles extracted from the literature (piroxicam, ranitidine, phenazopyridine and talinolol). Visual inspection and statistical diagnostics showed that the present algorithm provided adequate curve fit disregarding the mechanism involved in the emergence of the secondary peaks. Statistical diagnostic parameters (RSS, AIC and R2) generally showed good fitness in the plasma profile prediction by this model. It was concluded that the algorithm presented herein provides adequate predicted curves in cases of the double peak phenomenon. Copyright © 2006 John Wiley & Sons, Ltd. [source] Field-Flow Fractionation as Analytical Technique for the Characterization of Dry Yeast: Correlation with Wine Fermentation ActivityBIOTECHNOLOGY PROGRESS, Issue 6 2003Ramsés Sanz Important oenological properties of wine depend on the winemaking yeast used in the fermentation process. There is considerable controversy about the quality of yeast, and a simple and cheap analytical methodology for quality control of yeast is needed. Gravitational field flow fractionation (GFFF) was used to characterize several commercial active dry wine yeasts from Saccharomycescerevisiae and Saccharomyces bayanus and to assess the quality of the raw material before use. Laboratory-scale fermentations were performed using two different S. cerevisiae strains as inocula, and GFFF was used to follow the behavior of yeast cells during alcoholic fermentation. The viable/nonviable cell ratio was obtained by flow cytometry (FC) using propidium iodide as fluorescent dye. In each experiment, the amount of dry wine yeast to be used was calculated in order to provide the same quantity of viable cells. Kinetic studies of the fermentation process were performed controlling the density of the must, from 1.071 to 0.989 (20/20 density), and the total residual sugars, from 170 to 3 g/L. During the wine fermentation process, differences in the peak profiles obtained by GFFF between the two types of commercial yeasts that can be related with the unlike cell growth were observed. Moreover, the strains showed different fermentation kinetic profiles that could be correlated with the corresponding fractograms monitored by GFFF. These results allow optimism that sedimentation FFF techniques could be successfully used for quality assessment of the raw material and to predict yeast behavior during yeast-based bioprocesses such as wine production. [source] | |||||||||||||