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The more precise mathematical definition is that there is never translational symmetry in more than n – 1 linearly independent directions, where n is the dimension of the space filled, e.g., the three-dimensional tiling displayed in a quasicrystal may have translational symmetry in two directions.
Non-cellular life, also known as acellular life, is life that exists without a cellular structure for at least part of its life cycle. [1] Historically, most definitions of life postulated that an organism must be composed of one or more cells, [2] but, for some, this is no longer considered necessary, and modern criteria allow for forms of life based on other structural arrangements.
An aperiodic tiling is a non-periodic tiling with the additional property that it does not contain arbitrarily large periodic regions or patches. A set of tile-types (or prototiles) is aperiodic if copies of these tiles can form only non-periodic tilings. The Penrose tilings are a well-known example of aperiodic tilings. [1] [2]
A tiling that cannot be constructed from a single primitive cell is called nonperiodic. If a given set of tiles allows only nonperiodic tilings, then this set of tiles is called aperiodic . [ 3 ] The tilings obtained from an aperiodic set of tiles are often called aperiodic tilings , though strictly speaking it is the tiles themselves that are ...
The uniformity of both specific types of molecules (the biomolecules) and of certain metabolic pathways are invariant features among the wide diversity of life forms; thus these biomolecules and metabolic pathways are referred to as "biochemical universals" [4] or "theory of material unity of the living beings", a unifying concept in biology ...
Biotic material, natural material, or natural product, a material produced by a living organism; Biomass, living or dead biological matter, often plants grown as fuel; Biomass (ecology), the total mass of living matter in a given environment, or of a given species; Body fluid, any liquid originating from inside the bodies of living people
[8] [9] [10] Active matter is a relatively new material classification in soft matter: the most extensively studied model, the Vicsek model, dates from 1995. [11] Research in active matter combines analytical techniques, numerical simulations and experiments.
Benign: present in some organisms, sometimes bioaccumulating, but generally having no apparent effects (except possible harmful effects, notes "a" or "b"). 1 Extremely rare on the Earth's surface (less than 1×10 −7 %, i.e. less than 1/10 as common as the least common essential element, selenium), thus has low potential for any kind of ...