Metastability

Examples in chemistry

With the room temperature, the Diamant is metastable because the transformation towards the stable condition carbon Graphite is extremely slow (nonobservable). At higher temperatures, the speed of transformation of phase would be increased and diamond would be transformed more quickly into graphite because the chemical Cinétique of transformation increases with the temperature. On the other hand, obtaining diamond starting from carbon graphite is not possible that at high temperature (several thousands of degrees) and under high pressure (several tens of thousands of bar). In general natural diamonds are formed in extreme cases of the terrestrial coat at the time of a phenomenon of Subduction.

Another example, the Martensite is, with room temperature, a metastable phase of steels because it has a structure of high temperature. One stabilizes it by a Trempe which makes it possible to preserve this structure, characterized by a high Dureté (tempered steel).

Example in biology

The carbonaceous compounds which constitute the living beings are metastable. A Enzyme is a biocatalyst able to establish weak connections with its substrate on the level of its active site. The released binding energy is at the origin of the lowering of the energy of activation (Ea) of the reaction. The reaction is then " activée" kinetically (law of Arrhenius). An enzyme can accelerate the constant reaction speed which it catalyzes: thus chemical reactions which are very slow, even infinimente slow (metastable state) without Catalyseur are accelerated until becoming usable for the Métabolisme.

Examples in physics

Water in Superfusion (example: freezing fogs). Pure water droplets in suspension in a very pure air him also, do not freeze with 0 °C. They remain liquid until - 39 °C. This state known as of Superfusion cease brutally as soon as the drop comes into contact with a foreign body (including a crystal of ice, ground or any other object) or when the temperature drops below -39 °C.

A solid Poutre resists the longitudinal compressive stresses well. However these constraints are much more important than those necessary to fold it if it is isolated straight line. It is the phenomenon of the Flambage, which is likely to cause mechanical catastrophes. It is of any importance for the conceiving engineer of the parts lengthened (rods, pillars) to know to estimate the load threshold where its part will be likely to flame.

Other examples

Rene Thom used it to indicate a “ catastrophe ” virtual, potential or latent, on the critical path of the differentiation or “ catastrophe ” of the morphogenesis or appearance of a new form accompanied by the disappearance of the old form. It is named “ chréode ” in embryology by Waddington to indicate the differentiation of the entourage of the ovule fertilized in placenta and embryo.

Andre Green, to indicate the borderline case of the Personality disorder borderline, which it describes as Métastable, to exceed the idea of a simple passage through an imaginary border between neurosis and psychosis. It joined the term “ Aufhebung ” of Hegel, used by Freud, which gives well an account of this phenomenon of disappearance-appearance-conservation.

Related concepts

Stability
Instability

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