Science / Spiders / Thon Rings: rings visible in the power spectrum of micrographs obtained by bright-field electron microscopy. These rings can be explained as the effect of the contrast transfer function, which modulates the Fourier transform of the object in a defocus-dependent way. Presence of axial astigmatism is evident from deviations of the Thon rings from perfect circular symmetry, defocus is gauged from the placement of the rings, and resolution can be gauged from the range of the rings. For these reasons, electron micrographs are routinely inspected by optical diffraction, prior to scanning and digital analysis.
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Entertainment / Literature / Palatal Dipthongization: A sound change in which either the ash or the /e/ sound in Old English words became a diphthong when preceded by palatal consonants. For instance, Modern English cheese comes from Old English ciese, w MORE
Technology / Radar / Range Rings Control: Range rings are displayed on the screen when selected by this control and provide a rough estimate of the distance to a target displayed on the screen. The distance between the range rings is usually MORE
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