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Fourier Transformation (fourier + transformation)
Selected AbstractsAutomated Evaluation of Kikuchi Patterns by Means of Radon and Fast Fourier Transformation, and Verification by an Artificial Neural Network,ADVANCED ENGINEERING MATERIALS, Issue 8 2003R.A. Schwarzer Automated crystal orientation measurement (ACOM) in the SEM by interpreting backscatter Kikuchi patterns (see Figure) has become a standard tool of quantitative texture analysis in materials science during the last decade. A Radon transformation of the diffraction pattern, in combination with a 1D fast Fourier transformation, enables the fast extraction of the positions of Kikuchi bands. The high-frequency coefficients of the 1D FFT are used to define pattern quality as a measure of lattice imperfection and residual stress of the real crystal structure. [source] Quantification of Chemical Striae in Inorganic Melts and Glasses through Picture ProcessingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2010Martin Jensen Chemical striations occur in various types of inorganic melts like lava and glass melts, and affect the physical properties of materials. This paper reports a quantitative study of the chemical striations in iron-rich aluminosilicate melts and glasses. In this study, an integrated method has been established, which consists of sample preparation, image acquiring, Fourier Transformation, and characteristic value determination. The principle of the established method is illustrated by picture processing-based simulation. The extent of the chemical striations and the diffusion length of the striae can be measured using this method. It is found that the extent of the chemical striations is rather sensitive to the melting technique. Furthermore, the impact of chemical diffusion and stirring on the extent of striations is revealed using the picture processing-based simulation approach. The diffusion process eliminates small striae and reduces the intensity of the larger ones. At a constant temperature, the diffusion determines the transformation rate of an inhomogeneous melt into a homogeneous one. During stirring, the size distribution of the large striae becomes broader, but the overall intensity of the striae becomes smaller. [source] 2325: Dynamic retinal vessel analysis , how different parameters create the whole pictureACTA OPHTHALMOLOGICA, Issue 2010I LANZL Purpose Dynamic vessel analysis is usually associated with the observation of the reaction of retinal vessels to a defined stimulus. The data which is generated this way may be further analysed with respect to the dynamic unstimulated and stimulated vessel behaviour. Assessment of different parameters may highlight different aspects of the underlying disease. Methods Vessel diameters of retinal vessel segments were assessed by Dynamic Vessel Analyzer (DVA) in healthy volunteers of different age groups and patients with diabetes, glaucoma and systemic hypertension. Mathematical analysis of unstimulated vessels was used to describe vessel wall characteristics. Methods of signal analysis including Fourier Transformation, spectral filtration, auto- and cross correlation were applied to evaluate characteristic oscillations and pulse wave propagation along the vessel. Results Characteristic different vessel behaviour and vessel wall conformation are obtained by dynamic quantitative evaluations from the unstimulated vessels in physiologic aging and disease. Conclusion Dynamic vessel analysis includes information which may lead to further understanding of the vascular status and underlying disease pathology. It is also feasible to assess pulse wave velocities in retinal arterioles und thus clinically characterize the elasticity of the upstream vasculature in health and disease. [source] Arterial stiffening and cardiac hypertrophy in a new rat model of type 2 diabetesEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 1 2006K.-C. Chang Abstract Background, We determined the effects of NIDDM on haemodynamic parameters describing arterial wall elasticity and cardiac hypertrophy in rats administered streptozotocin (STZ) and nicotinamide (NA), using the aortic impedance analysis. Methods, Male Wistar rats at 2 months were administered intraperitoneally 180 mg kg,1 of NA, 30 min before an intravenous injection of 50 mg kg,1 STZ, to induce type 2 diabetes. The STZ-NA rats were divided into two groups, 4 weeks and 8 weeks after induction of diabetes, and compared with untreated age-matched controls. Pulsatile aortic pressure and flow signals were measured by a high-fidelity pressure sensor and electromagnetic flow probe, respectively, and were then subjected to Fourier transformation for the analysis of aortic input impedance. Results, In each diabetic group, the experimental syndrome was characterized by a moderate and stable hyperglycaemia and a relative deficiency of insulin secretion. However, the 8-week but not the 4-week STZ-NA diabetic rats showed a decrease in cardiac output in the absence of any significant changes in mean aortic pressure, having increased total peripheral resistance. The diabetic syndrome at 8 weeks also contributed to an increase in aortic characteristic impedance, from 1·49 ± 0·33 (mean ± SD) to 1·95 ± 0·28 mmHg s mL,1 (P < 0·05), suggesting a detriment to the aortic distensibility in NIDDM. Meanwhile, the STZ-NA diabetic animals after 8 weeks had an increased wave reflection factor (0·46 ± 0·09 vs. 0·61 ± 0·13, P < 0·05) and decreased wave transit time (25·8 ± 3·8 vs. 20·6 ± 2·8 ms, P < 0·05). Ratio of the left ventricular weight to body weight was also enhanced in the 8-week STZ-NA diabetic rats. Conclusion, The heavy intensity with early return of the pulse wave reflection may augment systolic load of the left ventricle coupled to the arterial system, leading to cardiac hypertrophy in the rats at 8 weeks after following STZ and NA administration. [source] Automated Evaluation of Kikuchi Patterns by Means of Radon and Fast Fourier Transformation, and Verification by an Artificial Neural Network,ADVANCED ENGINEERING MATERIALS, Issue 8 2003R.A. Schwarzer Automated crystal orientation measurement (ACOM) in the SEM by interpreting backscatter Kikuchi patterns (see Figure) has become a standard tool of quantitative texture analysis in materials science during the last decade. A Radon transformation of the diffraction pattern, in combination with a 1D fast Fourier transformation, enables the fast extraction of the positions of Kikuchi bands. The high-frequency coefficients of the 1D FFT are used to define pattern quality as a measure of lattice imperfection and residual stress of the real crystal structure. [source] Spectral analysis of electrocorticographic activity during pharmacological preconditioning and seizure induction by intrahippocampal domoic acidHIPPOCAMPUS, Issue 8 2010P.M. Sawant Abstract Previously we have shown that low-dose domoic acid (DA) preconditioning produces tolerance to the behavioral effects of high-dose DA. In this study, we used electrocorticography (ECoG) to monitor subtle CNS changes during and after preconditioning. Young adult male Sprague-Dawley rats were implanted with a left cortical electrode, and acute recordings were obtained during preconditioning by contralateral intrahippocampal administration of either low-dose DA (15 pmoles) or saline, followed by a high-dose DA (100 pmoles) challenge. ECoG data were analyzed by fast Fourier transformation to obtain the percentage of baseline power spectral density (PSD) for delta to gamma frequencies (range: 1.25,100 Hz). Consistent with previous results, behavioral analysis confirmed that low-dose DA preconditioning 60 min before a high-dose DA challenge produced significant reductions in cumulative seizure scores and high level seizure behaviors. ECoG analysis revealed significant reductions in power spectral density across all frequency bands, and high-frequency/high-amplitude spiking in DA preconditioned animals, relative to saline controls. Significant correlations between seizure scores and ECoG power confirmed that behavioral analysis is a reliable marker for seizure analysis. The reduction ofpower in delta to gamma frequency bands in contralateral cortex does not allow a clear distinction between seizure initiation and seizure propagation, but does provide objective confirmation that pharmacological preconditioning by DA reduces network seizure activity. © 2009 Wiley-Liss, Inc. [source] PRIMUS: a Windows PC-based system for small-angle scattering data analysisJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2003Petr V. Konarev A program suite for one-dimensional small-angle scattering data processing running on IBM-compatible PCs under Windows 9x/NT/2000/XP is presented. The main program, PRIMUS, has a menu-driven graphical user interface calling computational modules to perform data manipulation and analysis. Experimental data in binary OTOKO format can be reduced by calling the program SAPOKO, which includes statistical analysis of time frames, averaging and scaling. Tools to generate the angular axis and detector response files from diffraction patterns of calibration samples, as well as binary to ASCII transformation programs, are available. Several types of ASCII files can be directly imported into PRIMUS, in particular, sasCIF or ILL-type files are read without modification. PRIMUS provides basic data manipulation functions (averaging, background subtraction, merging of data measured in different angular ranges, extrapolation to zero sample concentration, etc.) and computes invariants from Guinier and Porod plots. Several external modules coupled with PRIMUSvia pop-up menus enable the user to evaluate the characteristic functions by indirect Fourier transformation, to perform peak analysis for partially ordered systems and to find shape approximations in terms of three-parametric geometrical bodies. For the analysis of mixtures, PRIMUS enables model-independent singular value decomposition or linear fitting if the scattering from the components is known. An interface is also provided to the general non-linear fitting program MIXTURE, which is designed for quantitative analysis of multicomponent systems represented by simple geometrical bodies, taking shape and size polydispersity as well as interparticle interference effects into account. [source] Bayesian estimation of hyperparameters for indirect Fourier transformation in small-angle scatteringJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2000Steen Hansen Bayesian analysis is applied to the problem of estimation of hyperparameters, which are necessary for indirect Fourier transformation of small-angle scattering data. The hyperparameters most frequently needed are the overall noise level of the experiment and the maximum dimension of the scatterer. Bayesian methods allow the posterior probability distribution for the hyperparameters to be determined, making it possible to calculate the distance distribution function of interest as the weighted mean of all possible solutions to the indirect transformation problem. Consequently no choice of hyperparameters has to be made. The applicability of the method is demonstrated using simulated as well as real experimental data. [source] Fourier transformation of arterial Doppler waveforms of the lower extremityJOURNAL OF CLINICAL ULTRASOUND, Issue 6 2004Hong Gi Lee MD Abstract Purpose Although it is well known that the normal, triphasic pulsatile arterial Doppler waveform changes in shape as flow is impaired, interpretation of the waveform has largely been subjective. We aimed to describe the Doppler waveforms of the lower extremity objectively using Fourier transformation. Methods Sixty-eight zero-crossing detector arterial recordings from 25 lower extremities were grouped as follows: group 1, no ischemic symptoms with an ankle-brachial index (ABI) > 0.9 (n = 17, 8 limbs); group 2, no ischemic symptoms with ABI < 0.9 (n = 18, 5 limbs); group 3, symptoms of claudication (n = 19, 7 limbs); group 4, rest pain or tissue loss (n = 14, 5 limbs). The waveforms were Fourier transformed and their amplitudes and phases were compared up to the third harmonic (H3). Results Amplitudes of both the fundamental (H1) and second harmonic (H2) were predominant in group 1. In contrast, amplitudes of the H2 and H3 decreased with altered flow (p < 0.0001 for group 1 versus others). The phases of the H1 and H2 were delayed with altered flow (p < 0.05 for group 1 versus others). Phases of the H1 were different between group 2 and 4 (p < 0.05). The difference of phase between the H3 and H1 was shortened with altered flow (p < 0.05 for group 1 or 2 versus group 4). Multivariate analysis revealed that the relative amplitudes of the H2 and H3, the phases of the H1 and H2, and the relative phase of the H3 were significant discriminators among the groups. Conclusion Abnormal waveforms could be characterized by the predominant amplitude of the H1, phase delay of the H1 and H2, and shortening of the relative phase of the H3. These parameters may be useful in the evaluation of Doppler waveforms in patients with peripheral arterial disease. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:277,285, 2004 [source] "Sponge-like" structures in polymer blends: visualization, physico-mathematical analysis, and universalityMACROMOLECULAR SYMPOSIA, Issue 1 2002Takeji Hashimoto Mesoscopic structures formed during an ordering process in thermodynamically unstable, isometric, binary molecular mixtures were explored by time-resolved scattering (TRS) and laser scanning confocal microscopy (LSCM). Three-dimensional (3D) bicontinuous structures, which were constructed for the first time by time-resolved LSCM, were found to have a "sponge-like" structure composed of two phases. The structure factor obtained by 3D Fourier transformation of the sponge was found to be identical to that obtained by TRS, confirming that the sponge truly reflects the structural entities evolving in the system. Furthermore, the sponge was shown for the first time to be theoretically predictable by using 3D computer simulations based on the time-dependent Ginzburg-Landau theory. The sponge was subjected to differential geometrical analysis: its Gaussian curvature K, mean curvature H, and their distributions were successfully determined for the first time. The result revealed that the sponge has hyperbolic interfaces with area-averaged curvatures satisfying RF stationary waves integrated Fourier transform spectrometerMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2007S. Hemour Abstract We describe here a new type of analog correlators based on stationary waves recovery and spatial Fourier transformation. The theoretical basis of the stationary waves integrated Fourier transform spectrometer (SWIFTS) is first introduced. Based on robust physical principles validated by circuits type simulations, the spectrometer could be an interesting competitor to actual RF analog correlators. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1138,1142, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22375 [source] A complicated quasicrystal approximant ,16 predicted by the strong-reflections approachACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2010Mingrun Li The structure of a complicated quasicrystal approximant ,16 was predicted from a known and related quasicrystal approximant ,6 by the strong-reflections approach. Electron-diffraction studies show that in reciprocal space, the positions of the strongest reflections and their intensity distributions are similar for both approximants. By applying the strong-reflections approach, the structure factors of ,16 were deduced from those of the known ,6 structure. Owing to the different space groups of the two structures, a shift of the phase origin had to be applied in order to obtain the phases of ,16. An electron-density map of ,16 was calculated by inverse Fourier transformation of the structure factors of the 256 strongest reflections. Similar to that of ,6, the predicted structure of ,16 contains eight layers in each unit cell, stacked along the b axis. Along the b axis, ,16 is built by banana-shaped tiles and pentagonal tiles; this structure is confirmed by high-resolution transmission electron microscopy (HRTEM). The simulated precession electron-diffraction (PED) patterns from the structure model are in good agreement with the experimental ones. ,16 with 153 unique atoms in the unit cell is the most complicated approximant structure ever solved or predicted. [source] Anaesthetic properties of Propiscin (Etomidaat) and 2-phenoxyethanol in the common carp (Cyprinus carpio L.), neural and behavioural measuresAQUACULTURE RESEARCH, Issue 11 2009Bert Lambooij Abstract The objective of the study was to evaluate the anaesthetic effects of Propiscin (2% etomidate) and 2-phenoxyethanol on common carp (Cyprinus carpio L.) by observing neural and behavioural measures. When exposed to the anaesthetic agent, the carp lost equilibrium after approximately 90 s of exposure. They did not breathe and the controls did not respond to tail pinch or prick or 6 V at the skin of the upper jaw. A shift to lower frequencies on the electroencephalogram (EEG) and computing fast Fourier transformation was observed when exposed to water containing Propiscin or 2-phenoxyethanol. Heart rate was reduced after placement in the water containing an anaesthetic agent. It may be concluded from our results that common carp were immobilized and sedated, when exposed to water containing 2 mL L,1 Propiscin and immobilized and anaesthetized in water containing 0.5 mL L,1 2-phenoxyethanol. In addition, the use of EEG provides for a sound assessment of exposure of carp to these anaesthetics. [source] Polarizable atomic multipole X-ray refinement: application to peptide crystalsACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2009Michael J. Schnieders Recent advances in computational chemistry have produced force fields based on a polarizable atomic multipole description of biomolecular electrostatics. In this work, the Atomic Multipole Optimized Energetics for Biomolecular Applications (AMOEBA) force field is applied to restrained refinement of molecular models against X-ray diffraction data from peptide crystals. A new formalism is also developed to compute anisotropic and aspherical structure factors using fast Fourier transformation (FFT) of Cartesian Gaussian multipoles. Relative to direct summation, the FFT approach can give a speedup of more than an order of magnitude for aspherical refinement of ultrahigh-resolution data sets. Use of a sublattice formalism makes the method highly parallelizable. Application of the Cartesian Gaussian multipole scattering model to a series of four peptide crystals using multipole coefficients from the AMOEBA force field demonstrates that AMOEBA systematically underestimates electron density at bond centers. For the trigonal and tetrahedral bonding geometries common in organic chemistry, an atomic multipole expansion through hexadecapole order is required to explain bond electron density. Alternatively, the addition of interatomic scattering (IAS) sites to the AMOEBA-based density captured bonding effects with fewer parameters. For a series of four peptide crystals, the AMOEBA,IAS model lowered Rfree by 20,40% relative to the original spherically symmetric scattering model. [source] Does internal longitudinal microstructure of retinal veins change with age in medically healthy persons?ACTA OPHTHALMOLOGICA, Issue 2009KE KOTLIAR Purpose We demonstrated previously that roughness of the retinal arterial blood column measured along the vessel axis, termed longitudinal arterial profile (LAP) increases significantly in anamnesticly healthy volunteers with increasing age. Recently we have demonstrated age related changes in LAP of medically healthy persons. Whether longitudinal retinal venous profiles (LVP) are altered with age in this group is investigated. Methods 83 medically healthy volunteers were examined by Dynamic Vessel Analyzer (IMEDOS, Jena, Germany) using stimulation with flickering light. 3 age groups were formed: young (N=28, 30,2±4,3 years), middle age (N=28, 42,3±3,3 years) and seniors (N=27, 64,0±5,0 years). Included in the analysis were volunteers without medical vascular risk factors defined as: blood pressure < 140/90 mmHg, HDL > 35 mg/dl, LDL < 190 mg/dl and glucose levels < 110 mg/dl. Retinal venous diameters were measured along 1 mm vessel segments to obtain LVP. Differences were analyzed using Fourier transformation. Results In all age groups power spectra of LVP do not change during all stages of the venous response to the stimulation. There were no significant differences in LVP between the age groups. Venous diameters in middle-age group were reduced in comparison to the young group at all stages of vessel reaction (p<0,05). Conclusion Our results indicate that in contrast to retinal arteries retinal veins of validated healthy volunteers do not undergo age related microstructural changes. Hence previously reported age related decrease of retinal venous diameter might have physiologic origin due to reduced blood flow in retinal microcirculation with age, not because of structural changes of venous wall. [source] Microstructural alterations of the retinal arterial blood column along the vessel axis in healthy volunteers with ageACTA OPHTHALMOLOGICA, Issue 2009IM LANZL Purpose We demonstrated previously that roughness of the retinal arterial blood column measured along the vessel axis increases in anamnestically healthy volunteers with increasing age. We termed it longitudinal retinal arterial profile (LAP). Whether LAP is altered with age in medically supervised healthy persons is investigated. Methods 82 medically healthy volunteers were examined by Dynamic Vessel Analyzer (IMEDOS, Jena, Germany) using stimulation with flickering light. 3 age groups were formed: young (N=27, 30,5±4,3 years), middle age (N=28, 42,3±3,3 years) and seniors (N=27, 64,0±5,0 years). Included in the analysis were volunteers without medical vascular risk factors defined as: blood pressure < 140/90 mmHg, HDL > 35 mg/dl, LDL < 190 mg/dl and glucose levels < 110 mg/dl. Retinal arterial diameters were measured along 1 mm vessel segments to obtain LAP. Differences were analyzed using Fourier transformation. Results In all age groups LAP do not change during all stages of the arterial response. Arterial diameters in the senior group were reduced in comparison to the young group at all stages of the vessel reaction (p<0,05). There are differences in LAP between the age groups. Compared to young persons, seniors showed significantly diminished waves with a period of 417 µm at all stages of the arterial reaction, whereas young volunteers showed less pronounced waves with a period of 208 µm (p<0,05). Conclusion Our results represent the healthy aging process in retinal vasculature. Age related microstructural changes in longitudinal profiles of retinal arteries in medically healthy persons might be an indication for alterations in the vascular endothelium and smooth musculature. [source] Solution of the unsaturated soil moisture equation using repeated transformsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 15 2001S. G. Fityus Abstract An alternative method of solution for the linearized ,theta-based' form of the Richards equation of unsaturated flow is developed in two spatial dimensions. The Laplace and Fourier transformations are employed to reduce the Richards equation to an ordinary differential equation in terms of a transformed moisture content and the transform variables, s and ,. Separate analytic solutions to the transformed equation are developed for initial states which are either in equilibrium or dis-equilibrium. The solutions are assembled into a finite layer formulation satisfying continuity of soil suction, thereby facilitating the analysis of horizontally stratified soil profiles. Solution techniques are outlined for various boundary conditions including prescribed constant moisture content, prescribed constant flux and flux as a function of moisture change. Example solutions are compared with linearized finite element solutions. The agreement is found to be good. An adaptation of the method for treating the quasilinearized Richards equation with variable diffusivity is also described. Comparisons of quasilinear solutions with some earlier semi-analytical, finite element and finite difference results are also favourable. Copyright © 2001 John Wiley & Sons, Ltd. [source]
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