A T1 process (or topological rearrangement process of the first kind) I. Cantat, S. Cohen-Addad, F. Elias, F. Graner, R. Höhler, O. Pitois, F. Rouyer, A. Saint-Jalmes, "Foams: structure and dynamics", Oxford University Press, ed. S.J. Cox, 2013, is one of the main processes by which cellular materials such as

foam Foams are materials formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the reg ...

s or

biological tissues In biology, tissue is a biological organizational level between cells and a complete organ. A tissue is an ensemble of similar cells and their extracellular matrix from the same origin that together carry out a specific function. Organs are ...

change shapes. It involves four discrete objects such as

bubbles Bubble, Bubbles or The Bubble may refer to: Common uses * Bubble (physics), a globule of one substance in another, usually gas in a liquid ** Soap bubble * Economic bubble, a situation where asset prices are much higher than underlying fundame ...

drop Drop, DROP, drops or DROPS may refer to: * Drop (liquid) or droplet, a small volume of liquid ** Eye drops, saline (sometimes mydriatic) drops used as medication for the eyes * Drop (unit), a unit of measure of volume * Falling (physics), allowi ...

cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

, etc. The four objects are initially arranged in a plane in the following way. Objects A and B are in contact and objects C and D are on either side of the AB group and touching both A and B. The T1 process consists in breaking the contact between A and B and establishing the contact between C and D. When a significant number of rearrangement events such as T1 processes with similar orientations occur inside a foam or a tissue, the material correspondingly undergoes a deformation: it elongates in the direction in which neighbours depart (here, AB) while it contracts in the direction in which new neighbour pairs form (here, CD). As a result of the existence of the T1 and similar processes, materials made of these objects have a number of similar rheological properties. Among these,

plasticity Plasticity may refer to: Science * Plasticity (physics), in engineering and physics, the propensity of a solid material to undergo permanent deformation under load * Neuroplasticity, in neuroscience, how entire brain structures, and the brain it ...

allows them to be deformed irreversibly. For such materials, such irreversible deformations arise from the ability to rearrange their constitutive objects. Thus, the T1 process is the major mesoscopic ingredient of plasticity for these materials.

References

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