670 research outputs found

    Quel tableau géographique des paysages ligériens ?

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    Les paysages de la vallée de la Loire sont fortement marqués par la dynamique du fleuve et de ses affluents qui ont créé une mosaïque de terroirs avec les châteaux, les jardins, une diversité du bâti, des espaces agraires calqués sur les conditions pédoclimatiques. Ces paysages ont subi plusieurs révolutions, industrielles et agricoles, qui les ont profondément transformés. Nous vivons aujourd\u27hui une nouvelle révolution marquée par l\u27extension et la densification urbaine et par l\u27émergence de paysages-vitrines modelés par l\u27écologie et des usages essentiellement touristiques

    Observation and implications of the Epeak - Eiso correlation in Gamma-Ray Bursts

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    The availability of a few dozen GRB redshifts now allows studies of the intrinsic properties of these high energy transients. Amati et al. recently discovered a correlation between Epeak, the intrinsic peak energy of the νfν\nu f \nu spectrum, and Eiso, the isotropic equivalent energy radiated by the source. Lamb et al. have shown that HETE-2 data confirm and extend this correlation. We discuss here one of the consequences of this correlation: the existence of a 'spectral standard candle', which can be used to construct a simple redshift indicator for GRBs.Comment: Proceedings of the GRB 2003 Conference in SantaFe, 5 pages, 4 figure

    Thermionic charge transport in CMOS nano-transistors

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    We report on DC and microwave electrical transport measurements in silicon-on-insulator CMOS nano-transistors at low and room temperature. At low source-drain voltage, the DC current and RF response show signs of conductance quantization. We attribute this to Coulomb blockade resulting from barriers formed at the spacer-gate interfaces. We show that at high bias transport occurs thermionically over the highest barrier: Transconductance traces obtained from microwave scattering-parameter measurements at liquid helium and room temperature is accurately fitted by a thermionic model. From the fits we deduce the ratio of gate capacitance and quantum capacitance, as well as the electron temperature

    A CMOS silicon spin qubit

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    Silicon, the main constituent of microprocessor chips, is emerging as a promising material for the realization of future quantum processors. Leveraging its well-established complementary metal-oxide-semiconductor (CMOS) technology would be a clear asset to the development of scalable quantum computing architectures and to their co-integration with classical control hardware. Here we report a silicon quantum bit (qubit) device made with an industry-standard fabrication process. The device consists of a two-gate, p-type transistor with an undoped channel. At low temperature, the first gate defines a quantum dot (QD) encoding a hole spin qubit, the second one a QD used for the qubit readout. All electrical, two-axis control of the spin qubit is achieved by applying a phase-tunable microwave modulation to the first gate. Our result opens a viable path to qubit up-scaling through a readily exploitable CMOS platform.Comment: 12 pages, 4 figure

    Pauli spin blockade in CMOS double quantum dot devices

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    Silicon quantum dots are attractive candidates for the development of scalable, spin-based qubits. Pauli spin blockade in double quantum dots provides an efficient, temperature independent mechanism for qubit readout. Here we report on transport experiments in double gate nanowire transistors issued from a CMOS process on 300 mm silicon-on-insulator wafers. At low temperature the devices behave as two few-electron quantum dots in series. We observe signatures of Pauli spin blockade with a singlet-triplet splitting ranging from 0.3 to 1.3 meV. Magneto-transport measurements show that transitions which conserve spin are shown to be magnetic-field independent up to B = 6 T.Comment: 5 pages , 4 figure

    Mercosur: un análisis empírico desde el comercio exterior.

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    Este trabajo analiza el comportamiento del Mercado Común del Sur (MERCOSUR) durante 1990-2010 y está focalizado en los cuatro países fundadores del mismo (Argentina, Brasil, Paraguay y Uruguay). En primer lugar, el trabajo revisa los avances del MERCOSUR como proceso de integración económica desde el comercio intrazona (utilizando el Índice de Intensidad del Comercio) y desde el comercio extrazona. En segundo lugar, mediante métodos de datos de panel, estima una función de exportación con variables ponderadas. Los resultados sugieren que el proceso de integración ha sido parcial, y que los ingresos externos y el tipo de cambio real ponderados por el comercio parecen tener un impacto significativo sobre las exportaciones.http://cuadernos.uma.es/pdfs/pdf753.pdfpublishedVersionFil: Jacobo, Alejandro D. Universidad Nacional de Córdoba. Facultad de Ciencias Económicas; Argentina.Fil: Barraud, Ariel A. Universidad Nacional de Córdoba. Facultad de Ciencias Económicas; Argentina.Economía, Econometrí

    Glucose starvation-induced dispersal of pseudomonas aeruginosa biofilms is camp and energy dependent

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    Carbon starvation has been shown to induce a massive dispersal event in biofilms of the opportunistic pathogen Pseudomonas aeruginosa; however, the molecular pathways controlling this dispersal response remain unknown. We quantified changes in the proteome of P. aeruginosa PAO1 biofilm and planktonic cells during glucose starvation by differential peptide-fingerprint mass-spectrometry (iTRAQ). In addition, we monitored dispersal photometrically, as a decrease in turbidity/opacity of biofilms pre-grown and starved in continuous flow-cells, in order to evaluate treatments (e.g. inhibitors CCCP, arsenate, chloramphenicol, L-serine hydroxamate) and key mutants altered in biofilm development and dispersal (e.g. nirS, vfr, bdlA, rpoS, lasRrhlR, Pf4-bacteriophage and cyaA). In wild-type biofilms, dispersal started within five minutes of glucose starvation, was maximal after 2 h, and up to 60% of the original biomass had dispersed after 24 h of starvation. The changes in protein synthesis were generally not more than two fold and indicated that more than 100 proteins belonging to various classes, including carbon and energy metabolism, stress adaptation, and motility, were differentially expressed. For the different treatments, only the proton-ionophore CCCP or arsenate, an inhibitor of ATP synthesis, prevented dispersal of the biofilms. For the different mutants tested, only cyaA, the synthase of the intracellular second messenger cAMP, failed to disperse; complementation of the cyaA mutation restored the wild-type phenotype. Hence, the pathway for carbon starvation-induced biofilm dispersal in P. aeruginosa PAO1 involves ATP production via direct ATP synthesis and proton-motive force dependent step(s) and is mediated through cAMP, which is likely to control the activity of proteins involved in remodeling biofilm cells in preparation for planktonic survival. © 2012 Huynh et al

    On the study of boundary layer sediment transport processes using new developmental acoustic techniques

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    This study aims at presenting a set of novel acoustic flow and sediment measuring tools used in a complementary way for the investigation of fine-scale flow and sediment transport processes above a rippled sand bed under waves. Measurements were conducted in the 100m long wave channel at UPC-LIM with surface gravity waves generating migrating ripples on a mobile sand bed. The set of acoustic instrumentation consisted of an Acoustic 3D Ripple Profiler (3D-ARP), a novel Bedform And Suspended Sediment Imager (BASSI) and three Acoustic Concentration and Velocity Profilers (ACVP). Here we assess the ACVP’s and the BASSI.Postprint (published version

    Ultra-High-density 3D vertical RRAM with stacked JunctionLess nanowires for In-Memory-Computing applications

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    The Von-Neumann bottleneck is a clear limitation for data-intensive applications, bringing in-memory computing (IMC) solutions to the fore. Since large data sets are usually stored in nonvolatile memory (NVM), various solutions have been proposed based on emerging memories, such as OxRAM, that rely mainly on area hungry, one transistor (1T) one OxRAM (1R) bit-cell. To tackle this area issue, while keeping the programming control provided by 1T1R bit-cell, we propose to combine gate-all-around stacked junctionless nanowires (1JL) and OxRAM (1R) technology to create a 3-D memory pillar with ultrahigh density. Nanowire junctionless transistors have been fabricated, characterized, and simulated to define current conditions for the whole pillar. Finally, based on Simulation Program with Integrated Circuit Emphasis (SPICE) simulations, we demonstrated successfully scouting logic operations up to three-pillar layers, with one operand per layer
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