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A fold axis "is the closest approximation to a straight line that when moved parallel to itself, generates the form of the fold". [2] (Ramsay 1967). A fold that can be generated by a fold axis is called a cylindrical fold. This term has been broadened to include near-cylindrical folds. Often, the fold axis is the same as the hinge line. [3] [4]
The two main subclasses of Anthozoa are the Hexacorallia, members of which have six-fold symmetry and includes the stony corals, sea anemones, tube anemones and zoanthids; and the Octocorallia, which have eight-fold symmetry and includes the soft corals and gorgonians (sea pens, sea fans and sea whips), and sea pansies.
A high-index reflective subgroup is the prismatic octahedral symmetry, [4,3,2] (), order 96, subgroup index 4, (Du Val #44 (O/C 2;O/C 2) *, Conway ± 1 / 24 [O×O].2). The truncated cubic prism has this symmetry with Coxeter diagram and the cubic prism is a lower symmetry construction of the tesseract, as .
The vergence of a fold lies parallel to the surrounding surfaces of a fold, so if these surrounding surfaces are not horizontal, the vergence of the fold will be inclined. For a fold, the direction and the extent to which vergence occurs can be calculated from the strike and dip of the axial surfaces, along with that of the enveloping surfaces ...
C i (equivalent to S 2) – inversion symmetry; C 2 – 2-fold rotational symmetry; C s (equivalent to C 1h and C 1v) – reflection symmetry, also called bilateral symmetry. Patterns on a cylindrical band illustrating the case n = 6 for each of the 7 infinite families of point groups. The symmetry group of each pattern is the indicated group.
John Conway uses a variation of the Schoenflies notation, based on the groups' quaternion algebraic structure, labeled by one or two upper case letters, and whole number subscripts. The group order is defined as the subscript, unless the order is doubled for symbols with a plus or minus, "±", prefix, which implies a central inversion .
[[Category:Geology templates]] to the <includeonly> section at the bottom of that page. Otherwise, add <noinclude>[[Category:Geology templates]]</noinclude> to the end of the template code, making sure it starts on the same line as the code's last character.
A Penrose tiling with rhombi exhibiting fivefold symmetry. A Penrose tiling is an example of an aperiodic tiling.Here, a tiling is a covering of the plane by non-overlapping polygons or other shapes, and a tiling is aperiodic if it does not contain arbitrarily large periodic regions or patches.