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The crystallographic restriction theorem in its basic form was based on the observation that the rotational symmetries of a crystal are usually limited to 2-fold, 3-fold, 4-fold, and 6-fold. However, quasicrystals can occur with other diffraction pattern symmetries, such as 5-fold; these were not discovered until 1982 by Dan Shechtman .
The pattern represented by every finite patch of tiles in a Penrose tiling occurs infinitely many times throughout the tiling. They are quasicrystals: implemented as a physical structure a Penrose tiling will produce diffraction patterns with Bragg peaks and five-fold symmetry, revealing the repeated patterns and fixed orientations of its tiles ...
Therefore, the number of 2-, 3-, 4-, and 6-fold rotocenters per primitive cell is 4, 3, 2, and 1, respectively, again including 4-fold as a special case of 2-fold, etc. 3-fold rotational symmetry at one point and 2-fold at another one (or ditto in 3D with respect to parallel axes) implies rotation group p6, i.e. double translational symmetry ...
The pentagonal bifrustum is the dual polyhedron of a Johnson solid, the elongated pentagonal bipyramid.A Johnson solid is one of 92 strictly convex polyhedra that is composed of regular polygon faces but are not uniform polyhedra (that is, they are not Platonic solids, Archimedean solids, prisms, or antiprisms).
The observation of the ten-fold diffraction pattern lay unexplained for two years until the spring of 1984, when Blech asked Shechtman to show him his results again. A quick study of Shechtman's results showed that the common explanation for a ten-fold symmetrical diffraction pattern, a type of crystal twinning, was ruled out by his experiments ...
The Fivefold Scapular, also known as Redemptorist Scapular, is a sacramental made up of five best-known of the early scapulars in the Catholic Church: the Brown Scapular of the Carmelites, the Blue Scapular of the Immaculate Conception, the Black Scapular of the Servites, the Red Scapular of the Passion, and the White Scapular of the Most Holy Trinity.
Accordingly, each gross element has a five fold composition. It was also assumed that this process of division and recombination goes on till the gross elements are produced as a continuous unending process, with the processes of Srishti ("creation"), Stithi ("sustenance"), and Samhara ("dissolution") continuing without change or interruption.