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991.
Michael Andrec James H. Prestegard 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,130(2):217-232
The Bayesian perspective on statistics asserts that it makes sense to speak of a probability of an unknown parameter having a particular value. Given a model for an observed, noise-corrupted signal, we may use Bayesian methods to estimate not only the most probable value for each parameter but also their distributions. We present an implementation of the Bayesian parameter estimation formalism developed by G. L. Bretthorst (1990,J. Magn. Reson.88, 533) using the Metropolis Monte Carlo sampling algorithm to perform the parameter and error estimation. This allows us to make very few assumptions about the shape of the posterior distribution, and allows the easy introduction of prior knowledge about constraints among the model parameters. We present evidence that the error estimates obtained in this manner are realistic, and that the Monte Carlo approach can be used to accurately estimate coupling constants from antiphase doublets in synthetic and experimental data. 相似文献
992.
K.J. Liu M. Miyake P.E. James H.M. Swartz 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,133(2):291-298
Carbon based paramagnetic materials are frequently used for EPR oximetry, especiallyin vivo,but the EPR spectra of these materials often have more than one paramagnetic center and/or relatively low signal intensity. To determine whether the multi-components of carbon based materials could be separated and enriched in the active component, we used density gradient centrifugation to separate the materials into several fractions. We studied two types of coals, gloxy and Pocahontas, and found these materials to have large density distribution. The separated density fractions had very different EPR spectra and intensities. The active component from the coal material had a more homogeneous EPR signal and significantly increased EPR signal intensity, whereas for India ink, only slight changes were observed. This result can be very useful in the development of better probes for EPR oximetry. 相似文献
993.
Katalin E. Kövér Dušan Uhr?&#x;n Victor J. Hruby 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,130(2):162-168
A pulsed field gradient version of the sensitivity-enhanced 2D TOCSY experiment is proposed which yields high-quality spectra with improved sensitivity and a minimum of two scans pert1increment. For rapid acquisition of 1D TOCSY spectra, the 1D DPFGSE–TOCSY experiment was modified to include phase-encoded multiple-selective excitation followed by a simple spectral editing. Combination of these two building blocks is used in a sensitivity-enhanced 2D analog of the 3D TOCSY–TOCSY experiment which provides an efficient tool for resolving severely overlapped signals of oligomers in short experimental time. 相似文献
994.
I. Souza Azevedo E. Baggio Saitovitch M. Hücker B. Büchner H. Micklitz 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):313-315
57Fe M?ssbauer effect studies of La1.65Eu0.20Sr0.15CuO4 doped with 0.5 at% 57Fe performed in the temperature region 300 K >
T
> 4.2 K give an onset temperature for magnetic ordering of K. This temperature practically is the same as that found in Nd doped La2-xSrxCuO4. It indicates that the magnetic ordering temperature in the LTT phase of rare earth (RE) doped La2-xSrxCuO4 is independent of the RE moment. The direction of the 57Fe magnetic moment in the magnetically ordered state is within the CuO2 plane, while it has been found to be parallel to the c-axis in Nd doped La2-xSrxCuO4.
Received: 23 June 1998 / Accepted: 14 July 1998 相似文献
995.
996.
H. Hommel A. Touhami A. Halli A. P. LeGrand 《Journal of Polymer Science.Polymer Physics》1995,33(16):2189-2198
EPR spectroscopy of labeled poly(ethylene oxide) (PEO) grafted on silica has been used to characterize the conformation and local dynamics of the chains. Grafted molecules of MW 2000 with grafting ratios of 0.045, 0.057, 0.126, and 0.42 molecules/nm2 were in contact with benzene. The mobility of the label was compared with that observed for solution of PEO from very diluted to highly concentrated and even bulk PEO. Thus, the concentration inside the grafted layer could be evaluated and also the thickness, which evolves rather linearly with the grafting ratio. © 1995 John Wiley & Sons, Inc. 相似文献
997.
H.-J. Scheibe D. Drescher A. Kolitsch A. Mensch 《Fresenius' Journal of Analytical Chemistry》1995,353(5-8):690-694
Morphology and structure of amorphous carbon films deposited with a pulsed arc source (LASER-ARC) have been studied using microscopical methods (SEM, TEM and AFM), electron diffraction and spectroscopical investigation (EELS). The parameters of the arc source and the deposition conditions (substrate temperature) influence morphology and structure of deposited amorphous carbon films. Especially the incorporation and growth of particles, embedded in the film have been investigated. By particle analysis using an optical microscope a majority of particles that is smaller than 500 nm has been determined. The morphology has been also demonstrated similar by AFM and TEM images. Their number and size of particles is strongly influenced by the deposition temperature. The structure of amorphous film is characterized by the EELS-spectra, but the particle structure was not detectable. 相似文献
998.
We study the propagation of phase space singularities for the time dependent Schrödinger equation with potential having Coulomb-type singularities in space dimension equal tothree. We prove that the singularities (frequency set) of the solution are reflected by a Coulomb center exactly as in the classical problem, i.e. the frequency set follows theregularized trajectories of Classical Mechanics after a collision. 相似文献
999.
Within the framework of the Glashow-Salam-Weinberg model it is shown that the Higgs field mediates an attractive scalar gravitational interaction of Yukawa type between the elementary particles which become massive by the ground state of the Higgs field after symmetry breaking. 相似文献
1000.
H.G.C. Human N.P. Ferreira C.J. Rademeyer P.K. Faure 《Spectrochimica Acta Part B: Atomic Spectroscopy》1982,37(7):593-602
A method and computer program were developed for calculating the temperature of any part of a graphite furnace tube at any instant of time after onset of the heating cycle. Results for tubes of the Massman design show large differences in spatial temperature distributions during and at the end of the heating cycle when equilibrium is reached. When constant current is applied to contoured tubes, greater heating rates at the tube centres are obtained than with standard tubes. 相似文献