PubMed · 10505896
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T Bortfeld, U Oelfke. 1999. CT reconstruction from fan data using parallel backprojection.. https://doi.org/10.1118/1.598709
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Searching through and conducting Monte Carlo folding simulations on 10(6) different 27 mer sequences, we have selected a prionlike lattice model whose energy spectrum and folding properties demonstrate characteristic prion behavior. The energetic competition and structural partition between two closely spaced energy minima yield unique kinetic and thermodynamic properties that can be qualitatively compared with experimental results. Folding simulations indicate that the probability of reaching the first excited state from a denatured random conformation is much higher than the probability of reaching the global energy-minimum state.
Anomalous Rayleigh scatter is examined for dilute concentrations of the biomedically relevant element iodine in aqueous media including measurements with monochromatic synchrotron radiation in the vicinity of the iodine K-edge. The measurements agree with anomalous scatter-factor corrections to the form-factor approximation which has been shown to have good agreement with higher precision S-matrix calculations for small angle scatter over a wide range of energies but has not been adequately tested at the edge. Monte Carlo modelling, including the modelling of polarized Compton and Rayleigh scattered x-rays, is used to determine the relative contributions of the scatter and fluorescent components at the detector as well as the modelling of self-absorption and relative dose in the determination of detection limits. A Rayleigh scatter minimum of 28 barns/sr was observed at an energy 10 +/- 5 eV below the K-edge of iodine at a position predicted from an evaluation of the dispersion integral that includes bound-bound resonance contributions. Minimum detectable concentrations for observation of the anomalous Rayleigh scatter feature at an exposure of 10 mSv, predicted for iodine and iron, are 1 mg ml(-1) and 10 mg ml(-1), respectively. Upper limits to detection of the feature imposed by degradation of the signal by self-absorption are 0.021 g cm(-2) and 0.0029 g cm(-2) radiation lengths, respectively.