Surface currents in Hall devices

One hundred and forty years after his discovery, the Hall effect still deserves attention. If it is well-known that the Hall voltage measured in Hall bar devices is due to the electric charges accumulated at the edges in response to the magnetic field, the nature of the corresponding boundary conditions is still problematic. In order to study this out-of-equilibrium stationary state, the Onsager's least-dissipation principle is applied. It is shown that, beside the well-known expression of the charge accumulation and the corresponding Hall voltage, a longitudinal surface current proportional to the charge accumulation is generated. An expression of the surface current is given. The surface currents allow the Hall voltage to be stabilized at a stationary state, despite, e.g., the presence of leakage of charges at the edges

Release kinetics of 5-fluorouracil-loaded microspheres on an experimental rat glioma.

BACKGROUND: Biodegradable loaded systems are promising devices for controlled and sustained release of anticancer drugs to brain tumours. We investigated the influence of drug-release profiles of 5-fluorouracil-loaded microspheres designed for the treatment of malignant gliomas. MATERIALS AND METHODS: 2.5 mg 5-FU delivered by either fast. (1 formulation) or slow-(2 formulations) 5-FU release microspheres (MS) were tested in C6-glioma rat brains. Tumor response was assessed by T2-weighted MRI. RESULTS: All treated animals, whatever the release profile considered, displayed a comparable 50% increase in life span versus controls. Delays in C6-glioma development appeared to correspond to the in vitro release periods of MS. In terms of curative prospect, complete remission was only observed in 11% of 5-FU-treated animals (4 out of 38). CONCLUSION: Formulation was unambiguously implicated in the response observed after local delivery of 5-FU to glioma

Designing Bioactive Delivery Systems for Tissue Regeneration

The direct infusion of macromolecules into defect sites generally does not impart adequate physiological responses. Without the protection of delivery systems, inductive molecules may likely redistribute away from their desired locale and are vulnerable to degradation. In order to achieve efficacy, large doses supplied at interval time periods are necessary, often at great expense and ensuing detrimental side effects. The selection of a delivery system plays an important role in the rate of re-growth and functionality of regenerating tissue: not only do the release kinetics of inductive molecules and their consequent bioactivities need to be considered, but also how the delivery system interacts and integrates with its surrounding host environment. In the current review, we describe the means of release of macromolecules from hydrogels, polymeric microspheres, and porous scaffolds along with the selection and utilization of bioactive delivery systems in a variety of tissue-engineering strategies

Surface currents in Hall devices

International audienceOne hundred and forty years after his discovery, the Hall effect still deserves attention. If it is well-known that the Hall voltage measured in Hall bar devices is due to the electric charges accumulated at the edges in response to the magnetic field, the nature of the corresponding boundary conditions is still problematic. In order to study this out-of-equilibrium stationary state, the Onsager's least-dissipation principle is applied. It is shown that, beside the well-known expression of the charge accumulation and the corresponding Hall voltage, a longitudinal surface current proportional to the charge accumulation is generated. An expression of the surface current is given. The surface currents allow the Hall voltage to be stabilized at a stationary state, despite, e.g., the presence of leakage of charges at the edges

Courant de surface pour l'effet Hall

A variational approach is used in order to study the stationary states of Hall devices. Charge accumulation, electric potentials and electric currents are investigated on the basis of the Kirchhoff-Helmholtz principle of least heat dissipation. A simple expression for the state of minimum power dissipated-that corresponds to zero transverse current and harmonic chemical potential-is derived. It is shown that a longitudinal surface current proportional to the charge accumulation is flowing near the edges of the device. Charge accumulation and surface currents define a boundary layer over a distance of the order of the Debye-Fermi length. arXiv:1908.06282v1 [cond-mat.mes-hall

Resistant starch determination adapted to products containing high level of resistant starch

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Les microARNs pro-angiogeniques et/ou pro-hypoxiques comme outils de monitoring des patients atteints d’un gliome

CERVOXYNational audienc