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International audience; How to overcome fastly and reliably the challenges to foster the lithium-based salts exploitation for latent heat storage technologies? In situ and real time microscopy is used to understand the discrepancies between the theoretical and experimental macroscopic properties of materials via the microscopic mechanisms. The feasibility of this method on the inorganic lithium salts is demonstrated despite their air/moisture-sensitivity and the common belief pretending that LiOH cannot be used for the synthesis of new materials inside the microscope chamber due to its decomposition in dry environment or under vacuum. The deviation source of ~30% from the theoretical energy density of 434 kWh/m3 has been investigated through the case study of Li4Br(OH)3, an uncommon promising phase change material. The hydration/dehydration of the starting materials appears as one of the main parameters, with applied temperature protocols, eliciting the deviation towards different materials from the targeted one of interest, in terms of morphology and properties. This criterion, if not taken into account, could be disastrous for the storage capacity of a unit during its use. This study highlights solutions to avoid these deficiencies. The results consistency at microscale with those obtained at macroscale is also proved despite the different operating conditions

Liver sinusoidal endothelial cells (LSECs) possess fenestrae, which are key for the exchange between blood and hepatocytes. Alterations in their number or diameter have important implications for hepatic function in liver diseases. They are lost early in the development of hepatic fibrosis through a process called capillarization. In this study, we aimed to demonstrate whether in vitro dedifferentiated LSECs that have lost fenestrae are able to re-form these structures. Using stimulated emission depletion super-resolution microscopy in combination with transmission electron microscopy, we analyzed fenestrae formation in a model mimicking the capillarization process in vitro. Actin is known to be involved in fenestrae regulation in differentiated LSECs. Using cytochalasin D, an actin-depolymerizing agent, we demonstrated that dedifferentiated LSECs remain capable of forming fenestrae. Conclusion: We provide a new insight into the complex role of actin in fenestrae formation and in the control of their size and show that LSEC fenestrae re-formation is possible, suggesting that this process could be used during fibrosis regression to try to restore exchanges and hepatocyte functions.

Background information Liver sinusoidal endothelial cells (LSECs) possess fenestrae, open transcellular pores with an average diameter of 100 nm. These fenestrae allow for the exchange between blood and hepatocytes. Alterations in their number or diameter in liver diseases have important implications for hepatic microcirculation and function. Although decades of studies, fenestrae are still observed into fixed cells and we have poor knowledge of their dynamics. Results Using stimulated emission depletion (STED) super-resolution microscopy, we have established a faster and simplest method to observe and quantify fenestrae. Indeed, using cytochalasin D, an actin depolymerising agent known to promote fenestrae formation, we measure the increase of fenestrae number. We adapted this methodology to develop an automated method to study fenestrae dynamics. Moreover, with two-colour STED analysis, we have shown that this approach could be useful to study LSECs fenestrae molecular composition. Conclusions Our approach demonstrates that STED microscopy is suitable for LSEC fenestrae study. Significance This new way of analysing LSEC fenestrae will allow for expedited investigation of their dynamics, molecular composition and functions to better understand their function in liver pathophysiology.

Ultra-small superparamagnetic iron oxide nanoparticles (USPIOs) have been used as vascular contrast agents in magnetic resonance imaging (MRI), mainly for their capacity to generate negative contrast. To use USPIOs as positive contrast agents, it is necessary to achieve increased colloidal stability and signal-enhancement performance. Their molecular coatings must be carefully chosen so the vascular blood-pool contrast agents must lead to long blood turnover times. However, to avoid long-term toxicological effects, they must also be cleared rapidly through the urinary or the gastrointestinal pathways. In this context, highly stable USPIOs showing “positive” contrast in MRI and optimal clearance rates, call for the development of robust biocompatible molecular coatings. In the present study, USPIOs were stabilized with multidentate block copolymer (MDBC), using a one-pot polyol synthesis method in the presence of MDBC. Two types of MDBC having pendant COOH groups in the anchoring block were developed: a po...

International audience; Deposition of metals on TiO2 semiconductor particles (M-TiO2) results in hybrid Janus objects combining the properties of both materials. One of the techniques proposed to generate Janus particles is bipolar electrochemistry (BPE). The concept can be applied in a straightforward way for the site-selective modification of conducting particles, but is much less obvious to use for semiconductors. Herein we report the bulk synthesis of anisotropic M-TiO2 particles based on the synergy of BPE and photochemistry, allowing the intrinsic limitations, when they are used separately, to be overcome. When applying electric fields during irradiation, electrons and holes can be efficiently separated, thus breaking the symmetry of particles by modifying them selectively and in a wireless way on one side with either gold or platinum. Such hybrid materials are an important first step towards high-performance designer catalyst particles, for example for photosplitting of water.

Alginate-based hydrogels are widely used for the development of biomedical scaffolds in regenerative medicine. The use of sugar glass as a sacrificial template for fluidic channels fabrication within alginate scaffolds remains a challenge because of the premature dissolution of sugar by the water contained in the alginate as well as the relatively slow internal gelation rate of the alginate. Here, a new and simple method, based on a sugar glass fugitive ink loaded with calcium chloride to build sacrificial molds, is presented. We used a dual calcium cross-linking process by adding this highly soluble calcium source in the printed sugar, thus allowing the rapid gelation of a thin membrane of alginate around the sugar construct, followed by the addition of calcium carbonate and gluconic acid δ-lactone to complete the process. This innovative technique results in the rapid formation of ''on-demand'' alginate hydrogel with complex fluidic channels that could be used in biomedical applications such as highly vascularized scaffolds promoting pathways for nutrients and oxygen to the cells.

Liver sinusoidal endothelial cells (LSECs) possess fenestrae, open transcellular pores with an average diameter of 100 nm. These fenestrae allow for the exchange between blood and hepatocytes. Alterations in their number or diameter in liver diseases have important implications for hepatic microcirculation and function. Although decades of studies, fenestrae are still observed into fixed cells and we have poor knowledge of their dynamics.Using stimulated emission depletion (STED) super-resolution microscopy, we have established a faster and simplest method to observe and quantify fenestrae. Indeed, using cytochalasin D, an actin depolymerising agent known to promote fenestrae formation, we measure the increase of fenestrae number. We adapted this methodology to develop an automated method to study fenestrae dynamics. Moreover, with two-colour STED analysis, we have shown that this approach could be useful to study LSECs fenestrae molecular composition.Our approach demonstrates that STED microscopy is suitable for LSEC fenestrae study.This new way of analysing LSEC fenestrae will allow for expedited investigation of their dynamics, molecular composition and functions to better understand their function in liver pathophysiology.

Deposition of metals on TiO

New alternating copolymers derived from thieno[3,4-c]pyrrole-4,6-dione (TPD) and 2,7-carbazole moieties have been synthesized by Suzuki cross-coupling reaction and characterized. These polymers combine interesting properties such as good solubility and excellent thermal and air stability. The present studies indicate that the combination of TPD and 2,7-carbazole building blocks can be a very effective way to lower the HOMO energy level and ultimately to enhance the Voc of polymer solar cells. The Voc reported here (up to 1.07 V) is one of the highest observed for polymer:[60]PCBM bulk heterojunction devices, and preliminary results on the photovoltaic devices (power conversion efficiencies up to 1.8%) indicate that performance could probably be improved by increasing the molecular weights and by fine-tuning the electronic properties and the morphology.

We report on a novel laser source, emitting high energy (20 nanoJoule) femtosecond pulses, in a broad spectrum (250 nm). This source is easily tuned from 950 to 1200 nm, without any laser adjustment, and delivers sub-300 femtosecond pulses with a 10-nm spectral width.

International audience; Characteristics and nature of close surface defects existing in fused silica polished optical surfaces were explored. Samples were deliberately scratched using a modified polishing process in presence of different fluorescent dyes. Various techniques including Epi-fluorescence Laser Scanning Mode (ELSM) or STimulated Emission Depletion (STED) confocal microscopy were used to measure and quantify scratches that are sometimes embedded under the polished layer. We show using a non-destructive technique that depth of the modified region extends far below the surface. Moreover cracks of 120 nm width can be present ten micrometers below the surface.

One of the major concerns encountered in high power laser is the laser-induced damage of optical components. This is a main issue of the development of the Europe's biggest laser, known as Laser Mega Joule (LMJ) especially in the section where the beam wavelength is 351 nm. This study deals with the development of a laser treatment process to improve the laser damage resistance of silica optical components. First, by irradiating the component at 355 nm in the nanosecond regime, defects of the silica optic are revealed and evolve as damage. Next, the damaged sites are irradiated with a CO 2 laser at a 10.6 μm wavelength in order to melt and evaporate the silica in the damage neighborhood. In this study, we performed a variation of the CO 2 laser parameters to obtain the most efficient stabilization. To check this stabilization, damage resistance tests were performed with an UV laser representative of the LMJ (at 355 nm/2.5 ns). The results show that we can stabilize weak points and thereby make the component resistant to subsequent UV laser irradiation.

Significant improvement in the polishing process of fused silica optical components has increased their lifetimes at 351 nm. Nevertheless, for large laser facilities like the LaserMegaJoule (LMJ), zero defect optical components are not yet available. Therefore, a damage mitigation technique has been developed to prevent the growth of the laser-initiated damage sites. Because of the difficulty to produce mitigated sites with sufficiently large depth, the initial morphology of damage to mitigate is a critical issue. The aim of this work is to determine laser parameters (pulse duration, fluence) which permit us to initiate damage sites in accordance with our mitigation process. Confocal microscopy is used to observe damage sites that have sub-surface cracks and consequently to measure precisely the diameter and the depth of the area to mitigate.

During the development of the laser megajoule (LMJ), a high power laser facility dedicated to DT fusion, CEA has made important efforts to understand and improve laser induced damage threshold of fused silica optics at the wavelength of 351 nm. For several years, with various industrials and academics partners, we have focused on optimizing the grinding, lapping and polishing processes to increase materials performance. In this paper, we describe our efforts in various fields: subsurface damage characterization, lapping process simulation, diamond grinding and lapping machine instrumentations, ... Our concern is to control and manage the material removal at each step of the process in order to reduce the cracks region extension and thus to diminish the damage density.

The lifetime of silica optics in high power laser facility as the Laser MegaJoule (LMJ) is typically limited by the initiation of surface damages and their subsequent growth. To prevent this problem, a mitigation technique is used: it consists in a local melting of silica by CO2 laser irradiation on the damage site. Because of the difficulty to produce efficient mitigated sites with large depth, the characterization of damage site to mitigate is very important. In this context, confocal microscopy appears to be an efficient solution to detect precisely cracks present under the damage site.

Significant improvement in polishing processes of fused silica optical components, has increased optics lifetime at the wavelength of 351 nm. Nonetheless, for large laser operation facilities like the Laser MegaJoule (LMJ), zero defect optics are not yet available. Therefore a damage mitigation technique has been developed to prevent the growth of initiated damage sites: this technique consists in a local melting and evaporation of silica by CO2 laser irradiation on the damage site. Because of the difficulty to produce efficient mitigated sites with large depth, the initial depth of damage to mitigate is a critical issue. An aim of our work was to determine the real extension of the damage site (including fractures) for different laser pulse durations between 3 ns and 16 ns and at different laser fluences. The fractures are nondetectable in conventional microscopy. The depth of the damage can thus be underestimated. Hence confocal microscopy, was used to observe these sub-surface fractures and to measure precisely the depth of damage. Results show that the damage is 2 to 4 times wider than deeper and this ratio is independent of the pulse duration and of the fluence. With this new information, the mitigation process can now be optimized.

International audience; no abstract

We report on a new fiber delivery system for coupling a compact, turn-key infrared femtosecond laser into a multiphoton microscope. Using a hollow core photonics crystal fiber with minimized dispersion, we achieve beam propagation on distances up to 4 meters. We measured a pulse duration close to 300 fs at the output of the microscope, for a femtosecond laser pulse duration of 200 fs. We present experimental parameters and system optimisation, and compare images obtained with fiber coupling versus direct coupling of the femtosecond laser.

We report on a flexible multiphoton imaging system, suitable for simultaneous and efficient excitation of red (DsRed), yellow (YFP), green (GFP) and blue (DAPI) fluorophores. We used a simple, compact laser system, consisting of a 1 µm high energy diode-pumped oscillator and a tunable wavelength extension using a photonics crystal fibre. The combination of a near IR excitation wavelength, high energy per pulse for efficient three photon excitation and spectral extension for GFP excitation allows for high flexibility.We present experimental results of simultaneous and efficient imaging fluorophores couples from the UV to the red (DAPI-RFP, GFP-RFP).

We have applied a new, 1030 nm wavelength, infrared diode-pumped femtosecond laser source to multiphoton microscopy, and present comparative results on the efficiency of fluorescence generation versus wavelength for several fluorophores. It is shown that an emission wavelength of 1030 nm is optimal both for GFP and DsRed excitation.

International audience; We report an experimental investigation of fluorescence confocal microscopy as a tool to measure subsurface damage on grinded fused silica optics. Confocal fluorescence microscopy was performed with an excitation at the wavelength of 405 nm on fixed abrasive diamond grinded fused silica samples. We detail the measured fluorescence spectrums and compare them to those of oil based coolants and grinding slurries. We evidence that oil based coolant used in diamond grinding induces a fluorescence that marks the subsurface damages and eases its observation. Such residual traces might also be involved in the laser damage process.

Jean-Philippe Legros ecoute les couples a qui l’on vient d’apprendre la pathologie de leur futur petit. L’indicible de leur souffrance interroge toute la pratique de ce que nous nommons le diagnostic prenatal.

L’enfant, le droit a la reconnaissance de sa vie avant la vie.Qu’est ce qui a change dans l’evolution de la prise en charge des interruptions de grossesses? Le deuil perinatal (mort-in-utero, fausse-couche, I.M.G., mais aussi processus biologiques et psychiques) est a redefinir et interroge le clinicien a propos de la Loi de cet «entre-deux mondes». Le Droit des parents devrait faire en sorte que la Loi ne defasse pas l’enfant de son existence (le fœtus et l’euthanasie, le fantasme de mort passive, les pratiques de l’arret de vie in utero). Le geste fœticide au nom de la Loi (euthanasie, fantasme de mort passive, etc.), demande une redefinition du fœtus. Le fœticide aboutit a un non Droit, non statut, de l’enfant (pas de nom, pas de sepulture). Alors que la Loi voulait supprimer des faux morts nes, nous aboutissons a inventer journellement de faux morts-nes vivants.La notion de deuil perinatal se distingue en deuils et non deuils, deuil differentiel, notion de consolation, meme si le deuil d’une mere est une dette «a» vie.

International audience; To develop materials with enhanced electrochemical properties, an original synthesis strategy based on the exfoliation and restacking of manganese and cobalt layered transition metal oxides has been explored. Successful exfoliation yielded “building nanoblocks”, which were further reassembled in mixed nanocomposites, by modifications of electrostatic interactions in solution. Three methods were tested, differing by the acidification procedure and time of mixing. The restacking conditions play a key role on the microstructural homogeneity of the nanocomposites. Such a nanocomposite approach marrying a good electronic conductor (cobalt oxyhydroxide) with a pseudocapacitive material (manganese oxide) should thus be very beneficial for development of highly efficient pseudocapacitors.