W . F . Tivol

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  • W . F . Tivol
  • Acta crystallographica. Section A, Foundations of…
  • 1995
Unitarity, a fundamental principle of scattering theory, leads to the prediction of an essentially unique set of phases for the scattering amplitude from a complete knowledge of the differential cross section or, in the case of a crystal, from the diffracted intensities. The Sayre equation and all the direct methods of phasing following there from are(More)
Analysis of electron diffraction patterns from rat hemoglobin taken at 200 kV on a wet stage yields intensity data to a resolution of 2-3 A which are as reproducible as those from typical X-ray diffraction. Some crystals were so similar that the differences in measured intensities were insignificant (R = 0.056), but in other cases real differences between(More)
Deposits left by electrodes and biocompatibility test specimens implanted in brain or peripheral nerve were characterized by X-ray microprobe analysis, electron diffraction and stereoscopic imaging using a high-voltage electron microscope. Examination of thick (1-micron) sections of neural tissue confirmed that the electron-dense bodies found adjacent to(More)
Electron diffraction intensity data were collected at 1200 kV from thin epitaxially oriented crystals of copper perbromophthalocyanine (C32Br16CuN8) in a projection down molecular columns. Measured cell constants for the projection with cmm symmetry are d100 = 17.88 (9), b = 26.46 (15) A. The structure was determined by Fourier refinement after three(More)
High-voltage (1200 kV) electron diffraction intensities from approximately 100 A thick crystals of copper perchlorophthalocyanine are used to determine the molecular packing at atomic resolution, thus greatly exceeding the structure detail observed by electron microscopy. Initial crystallographic phases were determined by direct methods often used in X-ray(More)
This introduction describes the contributions to this topical issue, and in some cases gives observations on the importance and implications of these articles. Subsequently, there is a discussion of the phase problem and its solution using the unitary equation. This equation, which is true for all known scattering processes, provides a firm theoretical(More)
The Sayre equation was evaluated as a technique for phase refinement in electron crystallography. Atomic-resolution electron diffraction data from copper perchlorophthalocyanine were assigned phase values from the Fourier transforms of various experimental electron micrographs, including one at 2.3 A, containing errors due to lens astigmatism. In each case,(More)
Our recent paper' concerning the P-delayed-proton precursors "Ne and "Ar mentioned the observation of 'C, also a precursor, but contained no details of its proton spectrum. Previously, Hardy et al.' had observed the decay of 'C to result in two high-energy proton peaks riding on a continuum. However, they could not have observed protons much below 3 MeV(More)