Controlling crystallization and its absence: Proteins, colloids and patchy models

The ability to control the crystallization behaviour (including its absence) of particles, be they biomolecules such as globular proteins, inorganic colloids, nanoparticles, or metal atoms in an alloy, is of both fundamental and technological importance. Much can be learnt from the exquisite control that biological systems exert over the behaviour of proteins, where protein crystallization and aggregation are generally suppressed, but where in particular instances complex crystalline assemblies can be formed that have a functional purpose. We also explore the insights that can be obtained from computational modelling, focussing on the subtle interplay between the interparticle interactions, the preferred local order and the resulting crystallization kinetics. In particular, we highlight the role played by ``frustration'', where there is an incompatibility between the preferred local order and the global crystalline order, using examples from atomic glass formers and model anisotropic particles.Comment: 11 pages, 7 figure

Recherches sur l’oganisation des larves des Eph\ue9m\ue8rines

Volume: 13Start Page: 1End Page: 13

Etude sur l’\ue9tat parfait du Prospistoma punctifrons

Volume: 11Start Page: 1End Page: 1

VII.—On the perfect state of Prosopistoma punctifrons

Volume: 8Start Page: 73End Page: 8

On the systematic position of the genus Hero

Volume: 2Start Page: 196End Page: 19

On the organization of Truncatella

Volume: 16Start Page: 396End Page: 39

Darcy\u2013Carreau Model and Nonlinear Natural Convection for Pseudoplastic and Dilatant Fluids in Porous Media

The linear and weakly nonlinear stability analyses are carried out to study instabilities in Darcy\u2013B\ue9nard convection for non-Newtonian inelastic fuids. The rheological model considered here is the Darcy\u2013Carreau model, which is an extension to porous media of Carreau rheological model usually used in clear fuid media. The linear stability approach showed that the critical Rayleigh number and wave number corresponding to the onset of convection are the same as for Newtonian fuids. By employing weakly nonlinear theory, we derived a cubic Landau equation that describes the temporal evolution of the amplitude of convection rolls in the unstable regime. It is found that the bifurcation from the conduction state to convection rolls is always supercritical for dilatant fuids. For pseudoplastic fuids, however, the interplay between the macroscale properties of the porous media and the rheological characteristics of the fuid determines the supercritical or subcritical nature of the bifurcation. In the parameter range where the bifurcation is supercritical, we determined and discussed the combined efects of the fuid properties and the porous medium characteristics on the amplitude of convection rolls and the corresponding average heat transfer for both pseudoplastic and dilatant fuids. Remarkably, we found that the curves describing these efects collapse onto the universal curve for Newtonian fuids, provided the average apparent viscosity is used to defne Rayleigh number

Mollusques de la France et des r\ue9gions voisines.

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