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Biomedical subjects

F Nori

Publications and source records attributed to F Nori.

At least 19 recordsLinked to original sources
PubMed2001

Collective interaction-driven ratchet for transporting flux quanta.

We propose and study a novel way to produce a dc transport of vortices when applying an ac electrical current to a sample. Specifically, we study superconductors with a graduated random pinning density, which transports interacting vortices as a ratchet system. We show that a ratchet effect appears as a consequence of the long range interactions between the vortices. The pinned vortices create an asymmetric periodic flux density profile, which results in an asymmetric effective potential for the unpinned interstitial vortices. The latter exhibit a net longitudinal rectification under an applied transverse ac electric current.

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PubMed2001

Moving Wigner glasses and smectics: dynamics of disordered Wigner crystals.

We examine the dynamics of driven classical Wigner solids interacting with quenched disorder from charged impurities. For strong disorder, the initial motion is plastic, in the form of crossing winding channels. For increasing drive, there is a reordering into a moving Wigner smectic with the electrons moving in separate 1D channels. These different dynamic phases can be related to the conduction noise and I(V) curves. For strong disorder, we show criticality in the voltage onset just above depinning. We obtain the dynamic phase diagram for driven Wigner solids and demonstrate a finite threshold of force for transverse sliding, recently observed experimentally.

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PubMed2000

Critical dynamics of burst instabilities in the Portevin-Le Ch atelier effect.

We investigate the Portevin-Le Châtelier effect (PLC), by compressing Al-Mg alloys in a very large deformation range, and interpret the results from the viewpoint of phase transitions and critical phenomena. The system undergoes two dynamical phase transitions between intermittent (or "jerky") and "laminar" plastic dynamic phases. Near these two dynamic critical points, the order parameter 1/tau of the PLC effect exhibits large fluctuations, and "critical slowing down" (i.e., the number tau of bursts, or plastic instabilities, per unit time slows down considerably).

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