We study a model for the translocation of proteins across membranes through a nanopore using a ratcheting mechanism. When the protein enters the nanopore it diffuses in and out of the pore according to a Brownian motion. Moreover, it is bound by ratcheting molecules which hinder the diffusion of the protein out of the nanopore, i.e. the Brownian motion is reflected such that no ratcheting molec...

The present paper introduces a comprehensive model capable of describing the behavior of granular materials under cyclic loading. Its main thrust is the introduction of the “Chicago” law in a continuum approach to account for the ratcheting effects. It also emphasizes the rate-dependency as a dissipative mechanism which acts independently or jointly with the ratcheting effect. Non-associated pl...

The paper reports the development of an implicit numerical scheme for plane stress cyclic elasto-plasticity, capable integrating a wide range hardening rules, and simulating multi-axial ratcheting in metal structural components. Constitutive relations account von Mises yielding combination with mixed hardening. Emphasis is given to kinematic part, which described advanced multiple back-stress m...

In this paper the ratcheting behavior of carbon steel(ASTM A106B) and stainless steel(304L) elbows is studied under steady internal pressure and in-plane external moments at frequencies typical of seismic excitations. The finite element analysis with the nonlinear isotropic/kinematic (combined) hardening model has been used to evaluate ratcheting behavior of the elbows. Material parameters have...

Ratcheting-fatigue investigations have been carried out to understand the ratcheting-fatigue failure of carbon manganese steel (conforming to ASME specification of SA-333 Gr.6). Experiments have been conducted on pressurized pipe-elbow assembly subjected to reversible cyclic bending, to assess the failure mechanics owing to ratcheting-fatigue synergy. These studies are required to evaluate the ...

The evolutionary transition to multicellularity probably began with the formation of simple undifferentiated cellular groups. Such groups evolve readily in diverse lineages of extant unicellular taxa, suggesting that there are few genetic barriers to this first key step. This may act as a double-edged sword: labile transitions between unicellular and multicellular states may facilitate the evol...

A local constitutive model for anisotropic granular materials is introduced and applied to isobaric (homogeneous) axial-symmetric deformation. The simplified model (in the coordinate system of the bi-axial box) involves only scalar values for hydrostatic and shear stresses, for the volumetric and shear strains as well as for the new ingredient, the anisotropy modulus. The non-linear constitutiv...