While crystals can exhibit only two, three, four, or six-fold rotational symmetry, quasicrystals can exhibit seemingly "impossible" five-fold symmetry in two dimensions and icosahedral symmetry
in three dimensions.
central part made up of RNA, defensive shell of protein with icosahedral symmetry
, and additionally encased in lipid envelope of cellular origin (Beeck and Dubuisson, 2003).
The virus responsible for infectious myonecrosis (IMNV) has an icosahedral symmetry
with a diameter of around 40 nm, and its capsid is composed of 120 subunits with a floating density of 1.
This is the first new class of convex, equilateral polyhedra with icosahedral symmetry
in 400 years," says UCLA neuroscientist Stan Schein.
TiCrSi in initial state is characterized by presence of peaks of three phase components: quasi-crystalline [psi]-phase with icosahedral symmetry
and lattice spacing [alpha][psi] = 0.
Electron microscopic studies (8,15) have shown particles with a relatively smooth surface capsomeric structure and icosahedral symmetry
It had long been known that icosahedral symmetry
is not allowed for a periodic object (2).
Over half of all virus families have shells with icosahedral symmetry
The icosahedral symmetry
of the phase was demonstrated by carefully constructing a reciprocal lattice using a series of selected area electron diffraction.
using a computer to select a particular configuration of the 27 copies of p17 within a tile, the team then assembles all tiles according to the rules of icosahedral symmetry
X-ray scattering experiments demonstrate that these unusual materials appear to have a fivefold icosahedral symmetry
, a pattern that fails to fit conventional crystallographic rules.
Penrose also played the three-dimensional version of his tiling game -- packing space with simple blocks, such as pairs of squashed cubes (rhombohedra), that generate nonperiodic solid structures with fivefold or, in three dimensions, icosahedral symmetry