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Background Subtraction (background + subtraction)
Selected AbstractsLearning invariants to illumination changes typical of indoor environments: Application to image color correctionINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 3 2007B. Bascle Abstract This paper presents a new approach for automatic image color correction, based on statistical learning. The method both parameterizes color independently of illumination and corrects color for changes of illumination. This is useful in many image processing applications, such as image segmentation or background subtraction. The motivation for using a learning approach is to deal with changes of lighting typical of indoor environments such as home and office. The method is based on learning color invariants using a modified multi-layer perceptron (MLP). The MLP is odd-layered. The middle layer includes two neurons which estimate two color invariants and one input neuron which takes in the luminance desired in output of the MLP. The advantage of the modified MLP over a classical MLP is better performance and the estimation of invariants to illumination. The trained modified MLP can be applied using look-up tables, yielding very fast processing. Results illustrate the approach and compare it with other color correction approaches from the literature. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 132,142, 2007 [source] Data reduction practice in X-ray reflectometryJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2007F. Salah Data reduction practice in X-ray reflectometry is described. The several approaches for applying certain corrections, such as background subtraction, geometrical effects and normalization, are compared and discussed. Two widely employed setups, one with beam knife-edge and one without, are compared with respect to a number of corrections to be applied. [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] An algorithm for thorough background subtraction from high-resolution LC/MS data: application for detection of glutathione-trapped reactive metabolitesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2008Haiying Zhang Abstract A control sample background-subtraction algorithm was developed for thorough subtraction of background and matrix-related signals in high-resolution, accurate mass liquid chromatography/mass spectrometry (LC/MS) data to reveal ions of interest in an analyte sample. This algorithm checked all ions in the control scans within a specified time window around the analyte scan for potential subtraction of ions found in that analyte scan. Applying this method, chromatographic fluctuations between runs were dealt with and background and matrix-related signals in the sample could be thoroughly subtracted. The effectiveness of this algorithm was demonstrated using four test compounds, clozapine, diclofenac, imipramine, and tacrine, to reveal glutathione (GSH)-trapped reactive metabolites after incubation with human liver microsomes supplemented with GSH (30 µM compound, 45-min incubation). Using this algorithm with a ± 1.0 min control scan time window, a ± 5 ppm mass error tolerance, and appropriate control samples, the GSH-trapped metabolites were revealed as the major peaks in the processed LC/MS profiles. Such profiles allowed for comprehensive and reliable identification of these metabolites without the need for any presumptions regarding their behavior or properties with respect to mass spectrometric detection. The algorithm was shown to provide superior results when compared to several commercially available background-subtraction algorithms. Many of the metabolites detected were doubly charged species which would be difficult to detect with traditional GSH adduct screening techniques, and thus, some of the adducts have not previously been reported in the literature. Copyright © 2008 John Wiley & Sons, Ltd. [source] An algorithm for thorough background subtraction from high-resolution LC/MS data: application to the detection of troglitazone metabolites in rat plasma, bile, and urineJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2008Haiying Zhang Abstract Interferences from biological matrices remain a major challenge to the in vivo detection of drug metabolites. For the last few decades, predicted metabolite masses and fragmentation patterns have been employed to aid in the detection of drug metabolites in liquid chromatography/mass spectrometry (LC/MS) data. Here we report the application of an accurate mass-based background-subtraction approach for comprehensive detection of metabolites formed in vivo using troglitazone as an example. A novel algorithm was applied to check all ions in the spectra of control scans within a specified time window around an analyte scan for potential background subtraction from that analyte spectrum. In this way, chromatographic fluctuations between control and analyte samples were dealt with, and background and matrix-related signals could be effectively subtracted from the data of the analyte sample. Using this algorithm with a ± 1.0 min control scan time window, a ± 10 ppm mass error tolerance, and respective predose samples as controls, troglitazone metabolites were reliably identified in rat plasma and bile samples. Identified metabolites included those reported in the literature as well as some that had not previously been reported, including a novel sulfate conjugate in bile. In combination with mass defect filtering, this algorithm also allowed for identification of troglitazone metabolites in rat urine samples. With a generic data acquisition method and a simple algorithm that requires no presumptions of metabolite masses or fragmentation patterns, this high-resolution LC/MS-based background-subtraction approach provides an efficient alternative for comprehensive metabolite identification in complex biological matrices. Copyright © 2008 John Wiley & Sons, Ltd. [source] The influence of experimental and model uncertainties on EXAFS resultsJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001Hermann Rossner We analyze EXAFS oscillations in k-space with the FEFF code to obtain main-shell distances R, and mean-square displacement parameters ,i2 for all single and multiple scattering paths i in the shells , up to a maximum shell radius Rmax. To quantify the uncertainty in the determination of these model parameters we take into account experimental errors and uncertainties connected with background subtraction, with the approximate handling of the electronic many-body problem in FEFF, and with the truncation of the multiple scattering series. The impact of these uncertainties on the R, and ,i2 is investigated in the framework of Bayesian methods. We introduce an a priori guess of these model parameters and consider two alternative strategies to control the weight of the a priori input relative to that of the experimental data. We can take a model parameter space of up to 250 dimensions. Optionally we can also fit the coordination numbers Nj (j,,) and the skewness of the distribution of the R, besides the R, and ,i2. The method is applied to 10K Cu K-edge and 300K Au L3 -edge data to obtain model parameters and their a posteriori error correlation matrices. [source] Monitoring of Anti Cancer Drug Letrozole by Fast Fourier Transform Continuous Cyclic Voltammetry at Gold MicroelectrodeCHINESE JOURNAL OF CHEMISTRY, Issue 7 2010Parviz Norouzi Abstract A continuous cyclic voltammetric study of letrozole at gold microelectrode was carried out. The drug in phosphate buffer (pH 2.0) is adsorbed at ,200 mV, giving rise to change in the current of well-defined oxidation peak of gold in the flow injection system. The proposed detection method has some of advantages, the greatest of which are as follows: first, it is no more necessary to remove oxygen from the analyte solution and second, this is a very fast and appropriate technique for determination of the drug compound in a wide variety of chromatographic analysis methods. Signal-to-noise ratio has significantly increased by application of discrete Fast Fourier Transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. Also in this work some parameters such as sweep rate, eluent pH, and accumulation time and potential were optimized. The linear concentration range was of 1.0×10,7,1.0×10,10 mol/L (r=0.9975) with a limit of detection and quantitation 0.08 nmol/L and 0.15 nmol/L, respectively. The method has the requisite accuracy, sensitivity, precision and selectivity to assay letrozol in tablets. The influences of pH of eluent, accumulation potential, sweep rate, and accumulation time on the determination of the letrozol were considered. [source] Photometric properties and scaling relations of early-type Brightest Cluster GalaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008F. S. Liu ABSTRACT We investigate the photometric properties of the early-type Brightest Cluster Galaxies (BCGs) using a carefully selected sample of 85 BCGs from the C4 cluster catalogue with a redshift of less than 0.1. We perform accurate background subtractions and surface photometry for these BCGs to 25 mag arcsec,2 in the Sloan r band. By quantitatively analysing the gradient of the Petrosian profiles of BCGs, we find that a large fraction of BCGs have extended stellar envelopes in their outskirts; more luminous BCGs tend to have more extended stellar haloes that are likely to be connected with mergers. A comparison sample of elliptical galaxies was chosen with similar apparent magnitude and redshift ranges, for which the same photometric analysis procedure is applied. We find that BCGs have steeper size,luminosity (R,L,) and Faber,Jackson (L,,,) relations than the bulk of early-type galaxies. Furthermore, the power-law indices (, and ,) in these relations increase as the isophotal limits become deeper. For isophotal limits from 22 to 25 mag arcsec,2, BCGs are usually larger than the bulk of early-type galaxies, and a large fraction (,49 per cent) of BCGs have discy isophotal shapes. The differences in the scaling relations are consistent with a scenario where the dynamical structure and formation route of BCGs may be different from the bulk of early-type galaxies; in particular dry (dissipationless) mergers may play a more important role in their formation. We highlight several possible dry merger candidates in our sample. [source] | ||||||||||