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Results for “Deconvolution”

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At least 235 records · Page 13Linked to original sources

PubMed1974

X-ray small angle scattering. A new deconvolution method for evaluating electron density distributions from small angle scattering diagrams.

The direct determination of the electron density distributions of multilayered specimens with a small number of unit cells from X-ray small angle scattering experiments via the Q-function method of Hosemann and Bagchi includes the deconvolution of the so-called Q(o)-function, the generalized Patterson function of one unit cell. In this paper a new and direct deconvolution method on the basis of Fourier series is presented which is suitable for one-dimensional centrosymmetrical (or antisymmetrical) density distributions. A FORTRAN-program has been written which has an execution time of ca. 20 s on an UNIVAC 1106-computer. The procedure has been successfully tested on some convolution functions generated by membrane-type electron density distributions.

Computers↗

PubMed1983

Extension of the performance of Laplace deconvolution in the analysis of fluorescence decay curves.

The original Laplace deconvolution of luminescence data, obtained with pulsed systems, is reviewed. The system of equations from which the luminescence parameters can be determined is generalized for the case that describes the relaxation by a sum of exponentials. Artifacts such as scatter and time-shift can be taken into account. A modification of the original method that eliminates the iterative procedure in the estimation of the cut-off correction is suggested. This modified Laplace method is no longer restricted to the cases where the cut-off error is rather small and the exciting flash has a low tail. The possibility of the combination of several discrete experiments in a single Laplace deconvolution, without introducing new parameters or normalization factors, is shown. The merits of this combination method are demonstrated on a time-resolved depolarization experiment.

Luminescence↗

PubMed1995

Deconvolution of C-phycocyanin beta-84 and beta-155 chromophore absorption and fluorescence spectra of cyanobacterium Mastigocladus laminosus.

Absorption and fluorescence spectra of the C-phycocyanin beta-subunit were quantitatively deconvoluted into component spectra of the beta-84 and beta-155 chromophores. The deconvolution procedure was based on a theoretical treatment of polarization properties. Four kinds of spectra (absorption, emission, emission polarization, and excitation polarization) measured on C-phycocyanin isolated from the cyanobacterium Mastigocladus laminosus were used as the experimental data set. Without any assumption of spectral shape, the absorption and fluorescence spectra of both chromophores were unambiguously resolved and their fluorescence quantum yields were evaluated. By combining the spectra of the alpha-subunit, independently measured, with the resolved spectra of the beta-subunit, the fluorescence and fluorescence polarization spectra and the fluorescence quantum yield of the monomer were estimated; they agree with experimental values to within an acceptable error. Further, the matrix of energy transfer rates in the monomer was estimated; it gave a significantly different result (by up to 40%) from previously estimated ones.

Biophysical Phenomena↗

PubMed1985

Quantitative deconvolution of heavily fused chromatographic peaks of biological components using a multi-wavelength UV detector.

Quantitative deconvolution of a chromatographic peak with extremely low UV absorption (less than 0.005 A.U.) is demonstrated for the analysis of an anaesthetic (ketamine) in rabbit serum. One ketamine metabolite, nor-ketamine, was deconvoluted from a completely fused peak in the three-dimensional chromatogram by using a highly sensitive multi-wavelength UV detector. After injection of ketamine, the nor-ketamine level in the serum increased to 3 micrograms/ml, calculated as ketamine, in 120 min.

Animals↗

PubMed2000

Improvement of the lateral resolution of finite-size hydrophones by deconvolution

In various fields of ultrasound applications, frequencies well above 10 MHz are used. As a consequence of this, ultrasound sensors, especially the piezoelectric hydrophones presently available which are used for the characterization of the respective fields, can no longer be considered as point receivers. By means of numerical deconvolution, the adverse averaging effect caused by the finite sensor size can be revoked. The efficiency of the deconvolution process is dealt with for both numerical simulations and experimental investigations. Best results were obtained using a reconstruction filter consisting of a combination of a Wiener filter, a pruning filter and an additional low-pass filter.

Journal Article↗

PubMed2001

[Study of renal transplant by deconvoluted renogram with 99m Tc-mercaptoacetyltriglycine (Mag3)].

AIM: To evaluate the usefulness of the 99mTc-MAG3 renogram deconvolution and its derived parameters in kidney graft function monitoring. MATERIAL AND METHOD: 221 renograms were studied: 64 were diagnosed as functioning graft (FG), 37 as functioning graft with elevated serum creatinine (FG2), 59 as acute tubular necrosis (ATN), 30 as acute rejection (AR), 20 as urinary tract obstruction (OBS) and 11 as cyclosporine nephrotoxicity (TNX). The parameters evaluated were: maximal activity of conventional renogram and mean transit time (MTT), time to reach 20% (T20) and 80% (T80) of the height of the RRF and initial uptake (IU) from the deconvoluted renal retention function (RRF). RESULTS: MTT and T20 were significantly longer and IU significantly lower in non-functioning grafts. However, MTT and T20 became shorter than in FG when graft function is severely impaired. CONCLUSION: IU, MTT and T20 are more useful than maxim activity of renogram in monitoring kidney graft function and in evaluating renal dysfunction severity. IU is a very sensitive and early parameter.

Adult↗

PubMed2001

Image-spectroscopy--II. The removal of plural scattering from extended energy-filtered series by Fourier deconvolution.

The increased spectral information obtained by acquiring an EFTEM image-series over several hundred eV allows plural scattering to be removed from loss images using standard deconvolution techniques developed for the quantification of EEL spectra. In this work, both Fourier-log and Fourier-ratio deconvolution techniques have been applied successfully to such image-series. Application of the Fourier-log technique over an energy-loss range of several hundred eV has been achieved by implementation of a novel method that extends the effective dynamic range of EFTEM image-series acquisition by over four orders of magnitude. Experimental results show that the removal of plural scattering from EFTEM image-series gives a significant improvement in quantification for thicker specimen regions. Further, the recovery of the single-scattering distribution using the Fourier-log technique over an extended energy-loss range is shown to result in an increase in both the ionisation-edge jump-ratio and the signal-to-noise ratio.

Journal Article↗

PubMed2003

Deconvolution of electron diffraction patterns of amorphous materials formed with convergent beam.

To perform reduced density function (G(r)) analysis on electron diffraction patterns of amorphous materials formed with convergent beams, the effects of convergence must be removed from the diffraction data. Assuming electrons incident upon the sample in different directions are incoherent, this can be done using deconvolution (Ultramicroscopy 76 (1999) 115). In this letter we show that the combination of an energy filtering transmission electron microscope with an image plate, increases the accuracy with which diffraction data can be measured and, subsequently, the accuracy of the deconvolution.

Algorithms↗

PubMed2003

Rapid MR imaging by sensitivity profile indexing and deconvolution reconstruction (SPID).

A new parallel MR imaging technique, which uses localized information from the elements of a multi-coil array to accelerate imaging, is described. The technique offers an alternative reconstruction approach to currently available techniques (e.g., SMASH and SENSE). Following a partial k-space data acquisition, image reconstruction in this approach proceeds in two steps: first, fitting the measured coil sensitivities to a set of partially localized target functions, a blurred intermediate image of the studied object is produced. Blurring is obtained in a systematic manner, forming images of the studied object convolved with a known convolution kernel. Full spatial resolution is then recovered by deconvolution of the blurred images with the known kernel function. The technique offers flexibility in the arrangement of the acquired signal data k-lines, and a mechanism for controlling reconstruction quality through the convolution the deconvolution procedure. The technique was validated in phantom and in vivo imaging experiments demonstrating high time reduction factors.

Brain↗

PubMed1997

Rapid deconvolution of NMR powder spectra by weighted fast Fourier transformation.

The resolution enhancement conferred by numerical deconvolution of powder pattern spectra to spectra characteristic of a single alignment greatly simplifies solid state NMR spectral analysis. This is especially beneficial when the spectrum is a superposition of signals from multiple environments or sites of labelling. We have developed an innovative method to deconvolute (depake) spectra governed by axially symmetric second rank tensor interactions which possess a P2(cos theta) dependence upon orientation, where theta is the angle between the symmetry axis and the external magnetic field. Our approach differs substantially from previously published procedures which are iterative or require matrix inversion and, hence, are slow. The new method, instead, utilizes weighting functions in time and frequency domains to facilitate a rapidly executed solution based upon fast Fourier transformation (FFT). Its efficacy is demonstrated with 2H and 31P NMR data for model membranes.

Fourier Analysis↗

PubMed2003

Handling of computational in vitro/in vivo correlation problems by Microsoft Excel: III. Convolution and deconvolution.

Convolution and deconvolution are the classical in-vitro-in-vivo correlation tools to describe the relationship between input and weighting/response in a linear system, where input represents the drug release in vitro, weighting/response any body response in vivo. While functional treatment, e.g. in terms of polyexponential or Weibull distribution, is more appropriate for general survey or prediction, numerical algorithms are useful for treating actual experimental data. Deconvolution is not considered an algorithm by its own, but the inversion of a corresponding convolution. MS Excel is shown to be a useful tool for all these applications.

Algorithms↗

PubMedDate not supplied

Band deconvolution analysis of the absorption and magnetic circular dichroism spectral data of a planar phthalocyanine dimer.

The electronic absorption and magnetic circular dichroism spectral data of a phthalocyanine dicopper complex that is deduced to be very planar and to share a common benzene ring have been studied by band deconvolution analysis. The results were compared with those of the molecular orbital (MO) calculations within the framework of the Pariser-Parr-Pople (PPP) approximation. The results of the band deconvolution analysis are in good agreement with those of the PPP calculations, allowing many bands to be reasonably assigned on the basis of the MO calculations. The validity of the PPP method for the MO calculation of large molecules is also emphasized.

Circular Dichroism↗

PubMed2004

Comparison of changes in the secondary structure of unheated, heated, and high-pressure-treated beta-lactoglobulin and ovalbumin proteins using fourier transform raman spectroscopy and self-deconvolution.

Changes in protein secondary structure and conformation of ovalbumin and beta-lactoglobulin (15% protein w/w) were investigated by Fourier transform Raman spectroscopy and self-deconvolution. The amounts of alpha-helix, beta-sheets, random coil, and beta-turns in native beta-lactoglobulin were 15, 54, 6, and 25%, respectively, and those for ovalbumin (41, 34, 13, and 12%) compared well with published values obtained by X-ray crystallography. The proteins were heated at 90 degrees C for 30 min and high-pressure-treated at 600 MPa for 20 min. Heating increased beta-sheet structures in both proteins at the expense of alpha-helix; for beta-lactoglobulin beta-sheet structures increased from 54 to 70% and for ovalbumin, from 34 to 54%. Random coil increased from 6% in the native protein to 30% in high-pressure-treated beta-lactoglobulin. However, for ovalbumin, the contribution from beta-turns doubled in high-pressure-treated samples, with little change in random coil. Further examination of the deconvoluted amide I band in heated samples revealed several component bands. Bands at 1626 and 1682 cm(-1) for ovalbumin and at 1625 and 1680 cm(-1) for beta-lactoglobulin were observed and are associated with aggregated, intermolecular beta-sheet (beta-aggregation), indicative of heat denaturation. The band seen at 1632-1640 cm(-1) corresponded to intramolecular beta-sheet structures, whereas the band at 1625 cm(-1) is associated with exposed beta-sheets (for example, beta-strands with strong hydrogen bonding that are not part of the core of beta-sheets). In high-pressure-treated samples bands were also observed at 1628 and 1680 cm(-1) for ovalbumin and at 1626 and 1684 cm(-1) for beta-lactoglobulin, suggesting involvement of beta-sheet structures in protein aggregation. Raman bands were observed at 1665-1670 cm(-1) for ovalbumin and at 1663-1675 cm(-1) for beta-lactoglobulin due to random coil structures. The bands at 1650-1660 cm(-1) due to alpha-helices were observed in both heated and high-pressure-treated samples. In addition, in heated samples of both ovalbumin and beta-lactoglobulin, peak intensity increased for beta-sheet in the amide III region, 980-990 cm(-1), and decreased for helix structures (900-960 cm(-1)). In contrast, there was no peak at 1240 cm(-1) (amide III beta-sheet structures) in either high-pressure-treated ovalbumin or beta-lactoglobulin, suggesting that high-pressure denaturation at 600 MPa for 20 min is less extensive than heat denaturation at 90 degrees C for 30 min.

Fourier Analysis↗

PubMed2001

An extended point-area deconvolution approach for assessing drug input rates.

PURPOSE: To describe an extended point-area deconvolution approach for evaluating drug input rates based on the application of piecewise cubic polynomial functions. METHODS: Both the nonimpulse response data and the impulse reference data were independently represented by the piecewise cubic polynomials to obtain interpolations, numerical integration, and reduced step size for the staircase input rates. A moving average algorithm was employed to compute the input rate estimates. The method was illustrated using data from preclinical and human studies. Simulations were used to examine the effects of data noise. RESULTS: In all cases examined, the piecewise cubic interpolation functions combined with the moving average algorithm yielded estimates that were reasonable and acceptable. Compared to the standard point-area approach based on the trapezoidal rule, the present method resulted in estimates that were closer to the expected values. CONCLUSIONS: The point-area deconvolution analysis is one of the preferred approaches in assessing pharmacokinetic and biopharmaceutic data when it is undesirable to assume the functional forms of the input processes. The present method provides improved performance and greater flexibility of this approach.

Absorption↗

PubMed1992

Multiple oral administration of a ketoprofen-dextran ester prodrug in pigs: assessment of gastrointestinal bioavailability by deconvolution.

Deconvolution has been applied to estimate the in vivo dissolution/release process of ketoprofen from a ketoprofen-dextran ester prodrug in pigs. The prodrug was given to three pigs at intervals of 12 hr and in seven doses corresponding to 4 mg ketoprofen/kg body weight. Frequent blood sampling was carried out at the first, third, and seventh intervals. Plasma steady-state concentrations of ketoprofen following the prodrug administration were between 2 and 4 micrograms/ml. The reference consisted of a single p.o. dose of parent ketoprofen (4 mg/kg body weight). For each pig the response following the multiple dosing was deconvolved with the reference response using an algebraic deconvolution procedure adopted from the literature. The obtained cumulated in vivo dissolution/release profiles revealed similar release rates for the three pigs and similar extents of release (59, 70, and 65%). The mean in vivo dissolution/release times (MDT) were calculated to be 5.4, 6.1, and 5.7 hr, respectively. In conclusion, following administration of the dextran prodrug the plasma concentration curves and the dissolution/release profiles are uniform, with small interindividual variations.

Administration, Oral↗

PubMed2003

Application of wavelet transforms and an approximate deconvolution method for the resolution of noisy overlapped peaks in DNA capillary electrophoresis.

A new procedure for resolving noisy overlapped peaks in DNA separations by capillary electrophoresis (CE) is developed. The procedure combines both a wavelet-based denoising method that effectively denoises the signal and a novel approximate deconvolution technique that resolves the fragment peaks and improves the ability to separate highly overlapped peaks early in the electrophoresis process. Different kinds of overlapped peaks with and without noise simulated by computer as well as some DNA experimental electropherograms were submitted to the new procedure. A second order differential operator with variable coefficients is applied to the entire electrophoresis signal at any given time and approximate deconvolutions of the individual Gaussian peaks are performed. The operator incorporates the effect of the superposition and gives exact annihilation in the neighborhood of each peak. Overlapped peaks with a resolution higher than 0.46 can be resolved directly. Also, the method can determine the peak components of signals with a signal to noise ratio higher than 1.4

DNA Fragmentation↗

PubMedDate not supplied

Applicability of deconvolution and nonlinear optimization for reconstructing optical images from near-field optical microscope images.

We have made a computer reconstruction of a nanometric optical image of a sample from an observed near-field optical image. The near-field microscope image used for investigation was obtained numerically in three dimensions with the finite-difference time-domain (FDTD) method. The sample is dielectric substrate containing nanometric two strips made of dielectric or metal. Deconvolution with non-negativity constraint is used to reconstruct the nanometric structure of dielectric strips, while nonlinear optimization is used to reconstruct the metallic strips. The difference in choice of reconstruction method between two samples comes from the difference in degree of interaction or multiple scattering of the sample structure and the probe. It is shown in the results, the resolution limit attainable in deconvolution is as fine as the size of aperture of probe.

Journal Article↗

PubMed1986

Deconvolution of non-Gaussian linear processes with vanishing spectral values.

We consider the problem of estimating the filter generating a non-Gaussian linear process and the deconvolution of that process when the spectral density of the process has zeros. Without using a minimum phase assumption we show that often if there are only finitely many zeros there are procedures to effect such an estimation and deconvolution.

Journal Article↗