Diminution de l'impact de la buée sur les propriétés optiques de surfaces transparentes par texturation de surface (S14)

La buée est un ensemble de gouttelettes d'eau qui se forment à la surface des objets. La formation de buée peut être problématique. Cela est, par exemple, le cas sur des surfaces transparentes où la présence de buée altère les propriétés de transmission de la lumière. Pour limiter la formation de buée, deux approches peuvent être envisagées : soit en limitant la présence d'eau sur les surfaces (traitement pour des surfaces hydrophobes), soit en étalant les gouttelettes pour créer un film d'eau uniforme de faible épaisseur (traitement pour des surfaces hydrophiles). Actuellement, les techniques industrielles utilisent surtout l'approche hydrophile en essayant de former des films d'eau. Cette approche hydrophile est obtenue par revêtement chimique des surfaces. L'inconvénient majeur de cette approche est double : tout d'abord il ne s'agit pas d'une stratégie pérenne. Avec le temps, les molécules se détachent de la surface ou perdent leur fonction. Ensuite, les traitements chimiques utilisés ne sont pas respectueux de l'environnement. Notre approche consiste à proposer un traitement physique de surface, par texturation topographique. Ce traitement anti-buée devra évidemment respecter les contraintes optiques imposées par les fonctions des surfaces. Afin d'étudier l'approche choisie, nous avons mis en place un dispositif de génération, de contrôle et de caractérisation de buée

Influence of the polypropylene structure to control the replication of nanostructures by injection molding

Depuis plusieurs années, on cherche à fonctionnaliser les surfaces des matériaux que ce soit pour le bio-médical, la recherche ou l'industrie des transports afin de leur conférer de nouvelles propriétés (antibuée, réduction du frottement, dégivrage...) sur la plupart des surfaces (polymères, métaux ou céramique). Parmi les techniques de traitement de surface, l'ablation au moyen de laser ultra-bref offre la possibilité d'élaborer des textures submicroniques, qui jouent un rôle essentiel dans le comportement au mouillage de ces matériaux. Toutefois, dans le cas de production en grande série, il est préférable pour des questions de coûts, de reproduire ces textures avec une technique de reproduction d'empreinte. Cette étude porte sur la réplication par injection plastique de topographies submicroniques multiéchelles sur deux polypropylènes semi-cristallins (PP). Il s'agit de comprendre l'influence d'une part des paramètres du procédé d'injection et d'autre part de l'architecture macromoléculaire sur la réplication de texturation. Pour cela, les pièces polymères ont été réalisées dans une presse industrielle à partir d'un insert amovible nanotexturé par irradiation laser femtoseconde. Pour caractériser les échantillons produits par injection, des mesures de mouillage, de topographie, de rhéologie et de chimie de surface ont été effectuées sur les échantillons injectés. Les résultats seront présentés et analysés afin d'interpréter le rôle de l'architecture du polymère et des paramètres du procédé

The Athena X-ray Integral Field Unit (X-IFU)

The X-ray Integral Field Unit (X-IFU) is the high resolution X-ray spectrometer of the ESA Athena X-ray observatory. Over a field of view of 5' equivalent diameter, it will deliver X-ray spectra from 0.2 to 12 keV with a spectral resolution of 2.5 eV up to 7 keV on similar to 5 '' pixels. The X-IFU is based on a large format array of super-conducting molybdenum-gold Transition Edge Sensors cooled at similar to 90 mK, each coupled with an absorber made of gold and bismuth with a pitch of 249 mu m. A cryogenic anti-coincidence detector located underneath the prime TES array enables the non X-ray background to be reduced. A bath temperature of similar to 50 mK is obtained by a series of mechanical coolers combining 15K Pulse Tubes, 4K and 2K Joule-Thomson coolers which pre-cool a sub Kelvin cooler made of a He-3 sorption cooler coupled with an Adiabatic Demagnetization Refrigerator. Frequency domain multiplexing enables to read out 40 pixels in one single channel. A photon interacting with an absorber leads to a current pulse, amplified by the readout electronics and whose shape is reconstructed on board to recover its energy with high accuracy. The defocusing capability offered by the Athena movable mirror assembly enables the X-IFU to observe the brightest X-ray sources of the sky (up to Crab-like intensities) by spreading the telescope point spread function over hundreds of pixels. Thus the X-IFU delivers low pile-up, high throughput (> 50%), and typically 10 eV spectral resolution at 1 Crab intensities, i.e. a factor of 10 or more better than Silicon based X-ray detectors. In this paper, the current X-IFU baseline is presented, together with an assessment of its anticipated performance in terms of spectral resolution, background, and count rate capability. The X-IFU baseline configuration will be subject to a preliminary requirement review that is scheduled at the end of 2018. The X-IFU will be provided by an international consortium led by France, the Netherlands and Italy, with further ESA member state contributions from Belgium, Czech Republic, Finland, Germany, Ireland, Poland, Spain, Switzerland and contributions from Japan and the United States.Peer reviewe

Another brick in the wall. Immigration and electoral preferences: Direct evidence from state ballots

Using information on actual ballots rather than survey data, we investigate the impact of immigration on both electoral outcomes and immigrant-related motives underlying political preferences. We take advantage of 94 votes, namely 54 policy propositions and 40 elections for candidates, that took place in Californian general elections between 2010 and 2018. We first analyze how the share of immigrants at the census tract level affects electoral outcomes. We find that a rise in immigration is associated with a decrease in people’s support for the Democratic party and for liberal measures. Using proposition topics, we show that this effect is driven by policies pertaining to redistribution, public good provision and justice/crime, while other propositions, less directly related to immigration are not impacted. The effect is stronger when immigrants are less assimilated and originate from poor and culturally distant countries

Urban Seismomorphoses Seismic Vulnerabilities, an Embarrassing Legacy

Seismic vulnerability challenges sustainable urbanism. Antioch, Manosque and Oran, three Mediterranean cities destroyed by earthquakes, demonstrate how preservation of urban patrimony protects populations. The methodological pattern “urban seismic patrimonial strategies” cross investment and patrimonial care demonstrate natural hazards mitigation as a factor of urban policy. Urban patrimonial managers are unaware of seismic threat which obliges them to explain liabilities. Buildings evolution observation indicates urban phases. According urban policy reshape urban morphology and amplify social vulnerability

Time dependency of the hydrophilicity and hydrophobicity of metallic alloys subjected to femtosecond laser irradiations

International audienceSurfaces of metallic alloys were laser-processed with femtosecond laser pulses of 800 nm, with different power densities. The effect of time on the wettability of these surfaces was investigated. A multi-scale roughness made of undulations was created after the laser processing. This specific surface topography allowed the occurrence of a Wenzel's state. This state clearly explains the high hydrophilicity and hydrophobicity observed respectively one day after laser treatment and several days later. The change from hydrophilicity to hydrophobicity occurred over time and is due to surface chemistry modifications. The creation of new hydrophobic functional groups on aluminum alloy surface, for example, was proposed to be responsible for the hydrophobic behavior observed on these surfaces

Preparation of boron nitride-based coatings on metallic substrates via infrared irradiation of dip-coated polyborazylene

International audienc

Preparation of Non Oxide Ceramic Coatings on various kind of Substrates using the Polymer Derived Ceramic Approach

International audienc

The effects of femtosecond laser-textured Ti-6Al-4V on wettability and cell response

International audienceTo study the biological activity effects of femtosecond laser-induced structures on cell behavior, TA6V sampleswere micro-texturedwith focused femtosecond laser pulses generating grooves of various dimensions on the micrometerscale (width: 25–75 μm; depth: 1–10 μm). LIPSS (Laser Induced Periodic Surface Structures) were alsogenerated during the laser irradiation, providing a supplementary structure (sinusoidal form) of hundreds ofnanometers at the bottom of the grooves oriented perpendicular (⊥ LIPPS) or parallel (// LIPPS) to the directionof these grooves. C3H10 T1/2 murine mesenchymal stem cells were cultivated on the textured biomaterials. Tohave a preliminary idea of the spreading of biological media on the substrate, prior to cell culture, contactangle measurement were performed. This showed that the post-irradiation hydrophilicity of the samples can decreasewith time according to its storage environment. The multiscale structuration either induced a collaborativeor a competitive influence of the LIPSS and grooves on the cells. It has been shown that cells individuallyand collectively were most sensitive to microscale grooves which were narrower than 25 μm and deeper than5 μm with ⊥ LIPPS. In some cases, cells were individually sensitive to the LIPSS but the cell layer organizationdid not exhibit significant differences in comparison to a non-textured surface. These results showed that cellsare more sensitive to the nanoscale structures (LIPSS), unless the microstructures's size is close to the cell sizeand deeper than 5 μm. There, the cells are sensitive to the microscale structures and go on spreading followingthese structures