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Matrix Solution (matrix + solution)
Selected AbstractsFlexible GMRES-FFT method for fast matrix solution: application to 3D dielectric bodies electromagnetic scatteringINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 6 2004R. S. Chen Abstract In this paper, the electromagnetic wave scattering is analysed by the efficient Krylov subspace iterative fast Fourier transform (FFT) technique in terms of the electric field integral equation (EFIE) for a dielectric body of general shape, inhomogeneity, and anisotropy. However, when the permittivity of the scatter becomes large, the convergence rate of Krylov subspace iterative methods slow down. Therefore, the inner,outer flexible generalized minimum residual method (FGMRES) is used to accelerate the iteration. As a result, nearly 10 times convergence improvement is achieved for high permittivity cases. Copyright © 2004 John Wiley & Sons, Ltd. [source] Identification of proteins directly from tissue: in situ tryptic digestions coupled with imaging mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2007M. Reid Groseclose Abstract A novel method for on-tissue identification of proteins in spatially discrete regions is described using tryptic digestion followed by matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) with MS/MS analysis. IMS is first used to reveal the protein and peptide spatial distribution in a tissue section and then a serial section is robotically spotted with small volumes of trypsin solution to carry out in situ protease digestion. After hydrolysis, 2,5-Dihydroxybenzoic acid (DHB) matrix solution is applied to the digested spots, with subsequent analysis by IMS to reveal the spatial distribution of the various tryptic fragments. Sequence determination of the tryptic fragments is performed using on-tissue MALDI MS/MS analysis directly from the individual digest spots. This protocol enables protein identification directly from tissue while preserving the spatial integrity of the tissue sample. The procedure is demonstrated with the identification of several proteins in the coronal sections of a rat brain. Copyright © 2007 John Wiley & Sons, Ltd. [source] Selective imaging of positively charged polar and nonpolar lipids by optimizing matrix solution compositionRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2009Yuki Sugiura Previous studies have shown that matrix-assisted laser desorption/ionization,imaging mass spectrometry (MALDI-IMS) is useful for studying the distribution of various small metabolites, particularly lipids. However, in this technique, selective ionization of the target molecules is imperative, particularly when analyzing small molecules. Since the sample clean-up procedures available for the MALDI-IMS of small metabolites are limited, the tissue sample will contain numerous molecular species other than the target molecules. These molecules will compete for ionization resulting in severe ion suppression. Hence, it is necessary to develop and optimize a sample preparation protocol for the target molecules. In this study, through model experiments using reference compounds, we optimized the composition of the matrix solution used for positively charged lipids in terms of the concentration of the organic solvent and presence/absence of alkali metal salts. We demonstrated that a high concentration of organic solvent in the matrix solution favors the preferential detection of lipids over peptides. The presence of alkali metal salts in the matrix solution was favorable for the detection of polar lipids, while a salt-free matrix solution was suitable for the detection of nonpolar lipids. Furthermore, potassium salts added to the matrix solution caused merging of various lipid adducts (adducts with proton, sodium, and potassium) into one single potassiated species. Using the optimized protocols, we selectively analyzed phosphatidylcholine (PC) and triacylglycerol (TG) with different fatty acid compositions in a rat kidney section. Copyright © 2009 John Wiley & Sons, Ltd. [source] Approximation method for high-degree harmonics in normal mode modellingGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2002R. E. M. Riva Summary For some loading applications, the normal modes approach to the viscoelastic relaxation of a spherical earth requires the use of spherical harmonics up to a high degree. Examples include postseismic deformation (internal loading) and sea level variations due to glacial isostatic adjustment (external loading). In the case of postseismic modelling, the convergence of the solution, given as a spherical harmonic expansion series, is directly dependent on loading depth and requires several thousands of terms for shallow earthquake sources. The particular structure of the analytical fundamental solutions used in normal mode techniques usually does not allow a straightforward calculation, since numerical problems can readily occur due to the stiffness of the matrices used in the propagation routines. Here we show a way of removing this stiffness problem by approximating the fundamental matrix solutions, followed by a rescaling procedure, in this way we can virtually go up to whatever harmonic degree is required. [source] Exhaustive approach to the coupling matrix synthesis problem and application to the design of high degree asymmetric filtersINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2007Richard J. Cameron Abstract In this paper a new approach to the synthesis of coupling matrices for microwave filters is presented. The new approach represents an advance on existing direct and optimization methods for coupling matrix synthesis, in that it will exhaustively discover all possible coupling matrix solutions for a network if more than one exists. This enables a selection to be made of the set of coupling values, resonator frequency offsets, parasitic coupling tolerance, etc. that will be best suited to the technology it is intended to realize the microwave filter with. To demonstrate the use of the method, the case of the recently introduced "extended box" coupling matrix configuration is taken. The extended box is a new class of filter configuration adapted to the synthesis of asymmetric filtering characteristics of any degree. For this configuration the number of solutions to the coupling matrix synthesis problem appears to be high and offers therefore some flexibility that can be used during the design phase. We illustrate this by carrying out the synthesis process of two asymmetric filters of 8th and 10th degree. In the first example a ranking criterion is defined in anticipation of a dual mode realization and allows the selection of a "best" coupling matrix out of 16 possible ones. For the 10th degree filter a new technique of approximate synthesis is presented, yielding some simplifications of the practical realization of the filter as well as of its computer aided tuning phase. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. [source] An efficient method for analyzing nonuniformly coupled microstrip linesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2005Dengpeng Chen Abstract This article presents an efficient method for analyzing nonuniformly coupled microstrip lines. By choosing a modal-transformation matrix, the coupled nonlinear differential equations describing the symmetric nonuniformly coupled microstrip lines are decoupled using even- and odd-mode parameters; the original problem is thus transformed into two single nonuniform transmission lines. A power-law function of arbitrary order and having two adjustable parameters is chosen to better approximate the equation coefficients. Closed-form ABCD matrix solutions are obtained and used to calculate the S -parameters of nonuniformly coupled microstrip lines. Numerical results for two examples are compared with those from a full-wave commercial package and experimental ones in the literature in order to demonstrate the accuracy and efficiency of this method. This highly efficient method is employed to optimize a cosine-shape 10-dB codirectional coupler, which has good return loss and high directivity performance over a wide frequency range. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source] Sensitive detection of phosphopeptides by matrix-assisted laser desorption/ionization mass spectrometry: use of alkylphosphonic acids as matrix additivesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2008Hiroki Kuyama Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been one of the most powerful tools for analyzing protein phosphorylation. However, it is frequently difficult to detect phosphopeptides with high sensitivity by MALDI-MS. In our investigation of matrix/matrix-additive substances for improving the phosphopeptide ion response in MALDI-MS, we found that the addition of low-concentration alkylphosphonic acid to the matrix/analyte solution significantly enhanced the signal of phosphopeptides. In this study, the combination of methanediphosphonic acid and 2,5-dihydroxybenzoic acid gave the best results. In addition to enhancing the signal of the phosphopeptides, alkylphosphonic acid almost completely eliminated the signals of sodium and potassium ion adducts. We report herein sensitive detection of phosphopeptides by MALDI-MS with the use of alkylphosphonic acids as matrix additives. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||