Optical in situ size determination of single lanthanide-ion doped oxide nanoparticles

International audienceWe show that the size of a lanthanide-ion doped nanoparticle can be accurately determined from its luminosity. The optically determined size distribution is in very good agreement with the distribution obtained from transmission electron microscopy. These data confirm that single nanoparticles are visualized in microscopy experiments. Nanoparticles as small as 13 nm are detectable with integration times of 500 ms. (c) 2006 American Institute of Physics

Synthetically Encoded Ultrashort-Channel Nanowire Transistors for Fast, Pointlike Cellular Signal Detection

Nanostructures, which have sizes comparable to biological functional units involved in cellular communication, offer the potential for enhanced sensitivity and spatial resolution compared to planar metal and semiconductor structures. Silicon nanowire (SiNW) field-effect transistors (FETs) have been used as a platform for biomolecular sensors, which maintain excellent signal-to-noise ratios while operating on lengths scales that enable efficient extra- and intracellular integration with living cells. Although the NWs are tens of nanometers in diameter, the active region of the NW FET devices typically spans micrometers, limiting both the length and time scales of detection achievable with these nanodevices. Here, we report a new synthetic method that combines gold-nanocluster-catalyzed vapor–liquid–solid (VLS) and vapor–solid–solid (VSS) NW growth modes to produce synthetically encoded NW devices with ultrasharp (<5 nm) n-type highly doped $(n^{++})$ to lightly doped (n) transitions along the NW growth direction, where $n^{++}$ regions serve as source/drain (S/D) electrodes and the n-region functions as an active FET channel. Using this method, we synthesized short-channel $n^{++}/n/n^{++}$ SiNW FET devices with independently controllable diameters and channel lengths. SiNW devices with channel lengths of 50, 80, and 150 nm interfaced with spontaneously beating cardiomyocytes exhibited well-defined extracellular field potential signals with signal-to-noise values of ca. 4 independent of device size. Significantly, these “pointlike” devices yield peak widths of $\sim 500 \mu s$, which is comparable to the reported time constant for individual sodium ion channels. Multiple FET devices with device separations smaller than $2 \mu m$ were also encoded on single SiNWs, thus enabling multiplexed recording from single cells and cell networks with device-to-device time resolution on the order of a few microseconds. These short-channel SiNW FET devices provide a new opportunity to create nanoscale biomolecular sensors that operate on the length and time scales previously inaccessible by other techniques but necessary to investigate fundamental, subcellular biological processes.Chemistry and Chemical BiologyEngineering and Applied Science

TLS- and inventory-based Magnitude – Frequency relationship for rockfall in Montserrat and Castellfollit de la Roca

Hazard scenarios are defined by a representative event of a certain magnitude, which corresponds to a frequency of occurrence or annual probability. In rockfall, scenario magnitude is identified by the total volume detached. Therefore, in diffuse hazard assessment it is crucial to fit this relationship magnitude/frequency, called McF, where cumulated frequency is quoted in spatial & temporal terms. Inventories are the classical source of data to deal with this objective. Last decade, TLS or digital photogrammetry monitoring came to offer a complementary approach. The samples obtained by the two methods have a specific coverage and each has its own lack of information that can be compensated together.Peer ReviewedPostprint (published version

Caractérisation de tissu osseux et de biomatériaux pour la régénération osseuse sur gros volume.

L’objectif de cette étude est de développer un processus expérimental de régénération de tissus osseux de grand volume. Une première étape vise à produire du matériau osseux à partir de lambeau de périoste vascularisé et à le caractériser grâce a des essais d’indentation. Ensuite, nous développons un process impliquant un biomatériau poreux et biodégradable utilisé comme réceptacle de cellules mésenchymateuses. Dans les deux cas, le nouveau matériau obtenu est étudié grâce à des tests mécaniques et biologiques

Rockfall Magnitude-Frequency Relationship Based on Multi-Source Data from Monitoring and Inventory

Quantitative hazard analysis of rockfalls is a fundamental tool for sustainable risk management, even more so in places where the preservation of natural heritage and people's safety must find the right balance. The first step consists in determining the magnitude-frequency relationship, which corresponds to the apparently simple question: how big and how often will a rockfall be detached from anywhere in the cliff? However, there is usually only scarce data on past activity from which to derive a quantitative answer. Methods are proposed to optimize the exploitation of multi-source inventories, introducing sampling extent as a main attribute for the analysis. This work explores the maximum possible synergy between data sources as different as traditional inventories of observed events and current remote sensing techniques. Both information sources may converge, providing complementary results in the magnitude-frequency relationship, taking advantage of each strength that overcomes the correspondent weakness. Results allow characterizing rockfall detachment hazardous conditions and reveal many of the underlying conditioning factors, which are analyzed in this paper. High variability of the hazard over time and space has been found, with strong dependencies on influential external factors. Therefore, it will be necessary to give the appropriate reading to the magnitude-frequency scenarios, depending on the application of risk management tools (e.g., hazard zoning, quantitative risk analysis, or actions that bring us closer to its forecast). In this sense, some criteria and proxies for hazard assessment are proposed in the paper

La longue séquence de Marchésieux: reconstitution de paléoenvironnements marins durant le premier cycle glaciaire de l'hémisphère nord

International audienceA l'échelle des cinq derniers millions d'années, les enregistrements paléoclimatiques restitués par les sédiments océaniques illustrent le contrôle des paramètres orbitaux (précession, obliquité et excentricité) sur le climat global. La tendance au refroidissement qui accompagne la fin du Néogène est ainsi marquée, vers -2,4 Ma, par le développement rapide des calottes de glace de l'hémisphère nord (Shackleton et al., 1984). Alors que l'histoire du climat global restituée par les enregistrements océaniques est sans cesse précisée, les données concernant l'évolution des environnements continentaux et côtiers au cours de ces changements restent essentiellement fragmentaires. Le forage effectué à Marchésieux (Manche; Normandie) a permis de réaliser une étude pluridisciplinaire de la signature de ce premier cycle glaciaire de l'hémisphère nord (Prétiglien). Les premiers résultats stratigraphiques, paléoenvironnementaux (eustatisme, température, paléobathymétrie) sont présentés