Bande magnétique

Résumé

thumb|Bandes magnétiques dans une bandothèque. La bande magnétique (ou ruban magnétique) est un ruban de film plastique enroulé sur une bobine, et dont une face est recouverte d'une fine couche de matériau magnétique. Elle permet l'enregistrement et la lecture d'informations analogiques ou numériques à l'aide d'un magnétophone (pour signal audio), d'un magnétoscope (pour signal vidéo) ou d’un enregistreur-lecteur de bandes magnétiques (pour données informatiques). On y lit les informations en mesurant l'aimantation de particules magnétiques (oxyde de fer) déposées sur une fine bande de film plastique souple. On y écrit en modifiant l'orientation de l'aimantation. La bande magnétique a été développée en Allemagne en 1928 par Fritz Pfleumer et était alors destinée à l’enregistrement du son. Elle succède à l’enregistrement magnétique sur fil, inventé par Oberlin Smith en 1888 et l’ingénieur danois Valdemar Poulsen en 1898 et présenté pour la première fois à l’Exposition universelle de 1

Source officielle

https://fr.wikipedia.org/wiki/Bande_magn%C3%A9tique

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Aerolysin nanopores decode digital information stored in tailored macromolecular analytes

Chan Cao, Nuria Cirauqui Diaz, Matteo Dal Peraro, Lucien Fabrice Krapp, Aleksandra Radenovic

Digital data storage is a growing need for our society and finding alternative solutions than those based on silicon or magnetic tapes is a challenge in the era of “big data.” The recent development of polymers that can store information at the molecular level has opened up new opportunities for ultrahigh density data storage, long-term archival, anticounterfeiting systems, and molecular cryptography. However, synthetic informational polymers are so far only deciphered by tandem mass spectrometry. In comparison, nanopore technology can be faster, cheaper, nondestructive and provide detection at the single-molecule level; moreover, it can be massively parallelized and miniaturized in portable devices. Here, we demonstrate the ability of engineered aerolysin nanopores to accurately read, with single-bit resolution, the digital information encoded in tailored informational polymers alone and in mixed samples, without compromising information density. These findings open promising possibilities to develop writing-reading technologies to process digital data using a biological-inspired platform.

2020

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Phase diagram of the spin-1 Heisenberg model with three-site interactions on the square lattice

Frédéric Alexis Michaud, Frédéric Mila

We study the spin S = 1 antiferromagnetic Heisenberg model on the square lattice with, in addition to the nearest-neighbor interaction, a three-site interaction of the form (S-i . S-j)(S-j . S-k) + H.c. This interaction appears naturally in a strong coupling expansion of the two-orbital, half-filled Hubbard model. For spin 1/2, this model reduces to a Heisenberg model with bilinear interactions up to third neighbors, with a second-neighbor interaction twice as large as the third-neighbor one, a very frustrated model with an infinite family of helical classical ground states in a large parameter range. Using a variety of analytical and numerical methods, we show that the spin-1 case is also very frustrated, and that its phase diagram is even richer, with possibly the succession of seven different phases as a function of the ratio of the three-site interaction to the bilinear one. The phases are either purely magnetic phases with collinear order or of mixed magnetic and quadrupolar character with helical order.

2013

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, , , , , ,

Drastic bacterial enhancement was observed when the Ag(3%)-TiO2 nanotubes were modified with FeOx (3%) magnetic oxide. On bare TiO2- nanotubes a reduction of 0.21og(10)CFU was observed within one hour under simulated low intensity solar light. Under similar conditions, a bacterial reduction of 2.5log(10)CFU was observed, on Ag(3%)TiO2 increasing to 6.0log(10)CFU on Ag(3%)-TiO2-FeOx(3%) magnetic nanotubes. The bacterial inactivation kinetics is strongly influenced by the addition of FeOx. The fast inactivation induced by the composite catalyst seems to involve an increase in the interfacial charge transfer (IFCT) compared to a 2-oxide composite photocatalyst. Stable recycling of the photocatalyst was observed leading to bacterial oxidation. The unambiguous identification of the radical intermediates: OH-radicals, O-singlet and the valence holes vb(h +) on the Ag-TiO2-FeOx interface showed that the valence band holes vb(h +) were the main oxidative intermediates leading to bacterial inactivation. Nanotubes size, crystallinity and bulk composition of magnetite 1% (0 = 51.0 degrees), anatase 5% (0 = 8.9 degrees), goethite 37.3% (0 = 9.0 degrees), silver 1% (0=2.7 degrees) was obtained by the Rietveld refinement for the Ag(3%)-TiO2-FeOx(3%) nanotubes. The redox chemistry during bacterial inactivation was determined by X-ray photoelectron spectroscopy (XPS). (C) 2016 Elsevier B.V. All rights reserved.

Elsevier2017

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