R. Mason

This article deals with the decision of the US Supreme Court of 21 June 2018, No. 17-494 (Wayfair v. South Dakota), which overruled decades of precedent to declare that the Constitution did not bar a US state from imposing obligations on remote sellers to collect tax on sales they made into the state, even if they had no physical presence there. This article describes Wayfair and provides some cautions about what it means for the US states and the rest of the world, especially Europe.

Implications of Wayfair

W. Hoppe

Generally it is not sufficiently appreciated that electron microscopy is in fact a diffraction method. In essential aspects electron microscopes are more closely related to X-ray diffracto· meters than to light microscopes. In electron microscopes monochromatized radiation and coherent illumination (never used in light microscopy) correspond in X-ray diffractometers to the primary beam with a small divergence. Imaging ina general sense can take place in interference experiments between a primary beam and a scattered beam, or between diffe rent deflected scattered beams. This leads to the realization of an old dream in diffracto metry, namely to a general experimental solution of the "phase problem". The most im pressive analogy, however, concerns the potential of the electron microscope as a tool for structure determination (where the radiation wavelenght is smaller than the atomic distan ces). It was therefore considered timely to treat this topic in this series. It was a fortunate cioncidence that in 1976 a Workshop on "Unconventional Electron Microscope Methods for the Investigation of Molecular Structures" (sponsored by the European Molecular Biology Organisation, the Deutsche Forschungsgemeinschaft and the Max-Planck-Gesell schaft) took place, and that most speakers presenting introductory lectures agreed to publish their contributions in an expanded version in this volume. This volume is thus not a symposium report in the usual sense since it contains the majority of these introductory lectures only.

R. Mason

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