Plasmonic Oligomers with Tunable Conductive Nanojunctions

International audienceEngineering plasmonic hot-spots is essential for applications of plasmonic nanoparticles. A particularly appealing route is to weld plasmonic nanoparticles together to form more complex structures sustaining plasmons with symmetries targeted to given applications. However, thecontrol of the welding and subsequent hotspot characteristic is still challenging. Herein, we demonstrate an original method that connects gold particles to their neighbors by another metal of choice. We first assemble gold bipyramids in a tip-to-tip configuration, yielding short chainsof variable length and grow metallic junctions in a second step. We follow the chain formation and the deposition of the second metal (i.e. silver or palladium) via UV/Vis spectroscopy and we map the plasmonic properties using electron energy loss spectroscopy. The formation ofsilver bridges leads to a huge redshift of the longitudinal plasmon modes into the mid-infrared region, while the addition of palladium results in a redshift accompanied by significant plasmon damping

Présentation

La première partie de ce volume réunit les textes des communications présentées lors de la journée d’étude interdisciplinaire consacrée à « La notion de « cause » à travers les sciences » et organisée le 20 juin 2005 par l’Université de Paris X - Nanterre (École doctorale Connaissance, Langage et Modélisation, Laboratoire MoDyCo, Laboratoire Ethologie et Cognitions comparées). A l’origine de cette journée se trouve l’ambition de définir le concept de « cause » en langue. L’étude linguistique ..

A numerical clone for VeRCoRs mock-up

Safety of Nuclear Power Plants (NPP) is EDF main priority. Lifetime Extension Management, which is an industrial and economical objective thus requires solid demonstrations of NPP ability to sustain long term operation. Concerning the reactor containment building, an extensive research program is currently done, centered on a mock-up of a reactor containment building at 1/3 scale. This mock-up named VeRCoRs (VErification Réaliste du COnfinement des RéacteurS) was built near Paris, and is highly instrumented so that its behavior is monitored from the beginning of the construction. One of the main technical objectives of the project is to understand aging of buildings made of prestressed reinforced concrete and its effect on leak tightness evolution. Actually, at a 1/3 scale, the drying process will be nine times faster so that the studies of ageing can be speeded up. In order to verify this speed up, a numerical clone of VeRCoRs is developed at EDF to simulate ageing processes using EDF simulation tools (Salome-Meca, Code_Aster). This numerical model is also necessary to understand the ageing of the mock-up and to analyse on-measurable quantities such as stresses fields. Numerical results are compared to measurements carried out for now in terms of temperature, deformations and displacements. Finally, a first idea of VeRCoRs representativeness is drawn

Predicting leakage of the VERCORS mock-up and concrete containment buildings - a digital twin approach

EDF operates a nuclear power generation fleet made up of 56 reactors. This fleet contains 24 reactors designed as double-walled concrete containment building. The inner concrete containment vessel has no metallic liner and is a prestressed reinforced concrete building. The inner concrete containment vessel is designed to withstand a severe accident, in terms of mechanical and sealing behaviour. The tightness of the containment is tested every 10 years, by carrying out a pressurization test and by measuring the leak rate. The leak rate is required to be below a regulatory threshold to continue operation of the concrete containment building for the next ten years. Ageing of concrete due to drying, creep and shrinkage leads to increase prestress loss and then leak rate with time. For some containment buildings, the leak rate gets closer to the regulatory threshold with time, so important coating programs are planned to mitigate and limit the leak rate under the regulatory threshold. Therefore, it is very important for EDF to have a concrete containment building leak rate prediction tool. To address this issue, an important research program around a 1/3 scale concrete containment building mock-up called "VERCORS" have been launched at EDF. The mock-up is heavily instrumented, and its materials (concrete, prestressing cables) have been widely characterized and studied. An important numerical effort has also been made to implement structural computations of the mock-up and to capitalize these computations as well as their post-processing (so as to compare automatically with the monitoring data) in what can be called a digital twin of the mock-up. This digital twin is now used to predict the leakage of VERCORS mock-up before yearly pressure test, and also to optimize the repair programs on the real containments

Assessment of AtlantOS impact

Assessment of the impact of AtlantOS in situ observing system for Copernicus Marine Service and seasonal predictio

Data-model comparison of soil–water δ 18 O at a temperate site in N. Spain with implications for interpreting speleothem δ 18 O

An understanding of how seasonal and longer-term d18O signals in meteoric precipitation (d18Op) are modified by percolation through soils is essential to link temporal changes in speleothem d18O to surface climatic conditions. This study focuses on modifications that occur in a relatively thick soil above a temperate cave site (La Garma, N. Spain). Monthly soil-water d18O (d18Osw) values at a depth of 60 cm through the year is only 14% of the range in d18Op, implying substantial homogenisation and attenuation of seasonal signals. A striking feature is that d18Osw values at 60 cm depth are lowest in summer and highest in winter, the opposite (anti-phase) to that observed in rainfall. Soil-water residence times of up to circa 6 months in the upper 60 cm of soil, and a matrix flow, piston-type infiltration behaviour with mixing is inferred. Evaporative effects on recovered soil-water d18O are minimal at this wet temperate site, in contrast with published results from arid and semi-arid sites. A soil-water model is presented to estimate monthly d18Osw as a function of air temperature and d18Op, incorporating effects such as variations in the amount of infiltrated water, changes in the ratio between evaporation and transpiration, mixing with antecedent soil moisture and small enrichments in 18O linked to evaporation and summer moisture deficits. Our model reproduces the observed d18Osw results, and produces d18Osw outputs in excellent agreement with d18O data for two monitored drip-water sites at La Garma cave that exhibit seasonal d18O variability. We conclude that simple evapotranspiration models that permit infiltration during months that have a positive hydrological balance only tend to under-estimate summer rainfall contributions. Overall, the study provides an improved framework for predicting d18Osw trends at temperate sites such as La Garma that have a relatively thick soil cover, as well as for understanding seasonal ranges and trends in d18O in cave drip-sites

The Copernicus Marine Environment Monitoring Service Ocean State Report

The Copernicus Marine Environment Monitoring Service (CMEMS) Ocean State Report (OSR) provides an annual report of the state of the global ocean and European regional seas for policy and decision-makers with the additional aim of increasing general public awareness about the status of, and changes in, the marine environment. The CMEMS OSR draws on expert analysis and provides a 3-D view (through reanalysis systems), a view from above (through remote-sensing data) and a direct view of the interior (through in situ measurements) of the global ocean and the European regional seas. The report is based on the unique CMEMS monitoring capabilities of the blue (hydrography, currents), white (sea ice) and green (e.g. Chlorophyll) marine environment. This first issue of the CMEMS OSR provides guidance on Essential Variables, large-scale changes and specific events related to the physical ocean state over the period 1993–2015. Principal findings of this first CMEMS OSR show a significant increase in global and regional sea levels, thermosteric expansion, ocean heat content, sea surface temperature and Antarctic sea ice extent and conversely a decrease in Arctic sea ice extent during the 1993–2015 period. During the year 2015 exceptionally strong large-scale changes were monitored such as, for example, a strong El Niño Southern Oscillation, a high frequency of extreme storms and sea level events in specific regions in addition to areas of high sea level and harmful algae blooms. At the same time, some areas in the Arctic Ocean experienced exceptionally low sea ice extent and temperatures below average were observed in the North Atlantic Ocean

Barcoding T Cell Calcium Response Diversity with Methods for Automated and Accurate Analysis of Cell Signals (MAAACS)

International audienceWe introduce a series of experimental procedures enabling sensitive calcium monitoring in T cell populations by confocal video-microscopy. Tracking and post-acquisition analysis was performed using Methods for Automated and Accurate Analysis of Cell Signals (MAAACS), a fully customized program that associates a high throughput tracking algorithm, an intuitive reconnection routine and a statistical platform to provide, at a glance, the calcium barcode of a population of individual T-cells. Combined with a sensitive calcium probe, this method allowed us to unravel the heterogeneity in shape and intensity of the calcium response in T cell populations and especially in naive T cells, which display intracellular calcium oscillations upon stimulation by antigen presenting cells

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ‘‘Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion