Upconversion channels in Er3+:ZBLALiP fluoride glass microspheres

We present results on the realization of a multicolour microspherical glass light source fabricated from the erbium doped fluoride glass ZBLALiP. Whispering gallery mode lasing and upconversion processes give rise to laser and fluorescent emissions at multiple wavelengths from the ultraviolet to the infrared. Thirteen discrete emissions ranging from 320 to 849 nm have been observed in the upconversion spectrum. A Judd-Ofelt analysis was performed to calculate the radiative properties of Er3+:ZBLALiP microspheres, including the radiative transition probabilities, the electric dipole strengths, the branching ratios and the radiative lifetimes of the transitions involved. We have also identified the primary processes responsible for the generation of the observed wavelengths and have shown that this material has an improved range of emissions over other erbium doped fluoride glasses

Temporal gene profiling of the 5XFAD transgenic mouse model highlights the importance of microglial activation in Alzheimer’s disease

International audienceBackground: The 5XFAD early onset mouse model of Alzheimer's disease (AD) is gaining momentum. Behavioral, electrophysiological and anatomical studies have identified age-dependent alterations that can be reminiscent of human AD. However, transcriptional changes during disease progression have not yet been investigated. To this end, we carried out a transcriptomic analysis on RNAs from the neocortex and the hippocampus of 5XFAD female mice at the ages of one, four, six and nine months (M1, M4, M6, M9). Results: Our results show a clear shift in gene expression patterns between M1 and M4. At M1, 5XFAD animals exhibit region-specific variations in gene expression patterns whereas M4 to M9 mice share a larger proportion of differentially expressed genes (DEGs) that are common to both regions. Analysis of DEGs from M4 to M9 underlines the predominance of inflammatory and immune processes in this AD mouse model. The rise in inflammation, sustained by the overexpression of genes from the complement and integrin families, is accompanied by an increased expression of transcripts involved in the NADPH oxidase complex, phagocytic processes and IFN-γ related pathways. Conclusions: Overall, our data suggest that, from M4 to M9, sustained microglial activation becomes the predominant feature and point out that both detrimental and neuroprotective mechanisms appear to be at play in this model. Furthermore, our study identifies a number of genes already known to be altered in human AD, thus confirming the use of the 5XFAD strain as a valid model for understanding AD pathogenesis and for screening potential therapeutic molecules

Controling the coupling properties of active ultrahigh-Q WGM microcavities from undercoupling to selective amplification

International audienceUltrahigh-quality (Q) factor microresonators have a lot of applications in the photonics domain ranging from low-threshold nonlinear optics to integrated optical sensors. Glass-based whispering gallery mode (WGM) microresonators are easy to produce by melting techniques, however they suffer from surface contamination which limits their long-term quality factor to a few 10^8 . Here we show that an optical gain provided by erbium ions can compensate for residual losses. Moreover it is possible to control the coupling regime of an ultrahigh Q-factor three port microresonator from undercoupling to spectral selective amplification by changing the pumping rate. The optical characterization method is based on frequency-swept cavity-ring-down- pectroscopy. This method allows the transmission and dispersive properties of perfectly transparent microresonators and intrinsic finesses up to 4.0x10^7 to be measured. Finally we characterize a critically coupled fluoride glass WGM microresonator with a diameter of 220 mm and a loaded Q-factor of 5.3x10^9 is demonstrated

Olfactory Stem Cells, a New Cellular Model for Studying Molecular Mechanisms Underlying Familial Dysautonomia

International audienceBackground: Familial dysautonomia (FD) is a hereditary neuropathy caused by mutations in the IKBKAP gene, the most common of which results in variable tissue-specific mRNA splicing with skipping of exon 20. Defective splicing is especially severe in nervous tissue, leading to incomplete development and progressive degeneration of sensory and autonomic neurons. The specificity of neuron loss in FD is poorly understood due to the lack of an appropriate model system. To better understand and modelize the molecular mechanisms of IKBKAP mRNA splicing, we collected human olfactory ecto-mesenchymal stem cells (hOE-MSC) from FD patients. hOE-MSCs have a pluripotent ability to differentiate into various cell lineages, including neurons and glial cells.Methodology/Principal Findings: We confirmed IKBKAP mRNA alternative splicing in FD hOE-MSCs and identified 2 novel spliced isoforms also present in control cells. We observed a significant lower expression of both IKBKAP transcript and IKAP/hELP1 protein in FD cells resulting from the degradation of the transcript isoform skipping exon 20. We localized IKAP/hELP1 in different cell compartments, including the nucleus, which supports multiple roles for that protein. We also investigated cellular pathways altered in FD, at the genome-wide level, and confirmed that cell migration and cytoskeleton reorganization were among the processes altered in FD. Indeed, FD hOE-MSCs exhibit impaired migration compared to control cells. Moreover, we showed that kinetin improved exon 20 inclusion and restores a normal level of IKAP/hELP1 in FD hOE-MSCs. Furthermore, we were able to modify the IKBKAP splicing ratio in FD hOE-MSCs, increasing or reducing the WT (exon 20 inclusion):MU (exon 20 skipping) ratio respectively, either by producing free-floating spheres, or by inducing cells into neural differentiation.Conclusions/Significance: hOE-MSCs isolated from FD patients represent a new approach for modeling FD to better understand genetic expression and possible therapeutic approaches. This model could also be applied to other neurological genetic diseases

Micrometre-long covalent organic fibres by photoinitiated chain-growth radical polymerization on an alkali-halide surface

On-surface polymerization is a promising technique to prepare organic functional nanomaterials that are challenging to synthesize in solution, but it is typically used on metal substrates, which play a catalytic role. Previous examples on insulating surfaces have involved intermediate self-assembled structures, which face high barriers to diffusion, or annealing to higher temperatures, which generally causes rapid dewetting and desorption of the monomers. Here we report the photoinitiated radical polymerization, initiated from a two-dimensional gas phase, of a dimaleimide monomer on an insulating KCl surface. Polymer fibres up to 1 μm long are formed through chain-like rather than step-like growth. Interactions between potassium cations and the dimaleimide’s oxygen atoms facilitate the propagation of the polymer fibres along a preferred axis of the substrate over long distances. Density functional theory calculations, non-contact atomic force microscopy imaging and manipulations at room temperature were used to explore the initiation and propagation processes, as well as the structure and stability of the resulting one-dimensional polymer fibres

Hydrothermal aging of cracking catalysts V. Vanadium passivation by rare-earth compounds soluble in the feedstock

This study was designed to passivate vanadium on an ultrastable Y zeolite-based FCC catalyst. The passivating agents are rare-earth compounds soluble in hydrocarbons (dysprosium and samarium naphthenate, lanthanum octoate) which are introduced on the catalyst at the same time as vanadium naphthenate. Adsorption measurements show that more than 90% of the zeolite structure is preserved after high-temperature hydrothermal treatments when La/V = 1. High-resolution analytical microscopy shows that vanadates (SMVO 4 , LaVO 4 ), in the form of small particles, are formed on the surface of the catalyst grains on the matrix and both on the external surface and in the mesopores of the zeolite. The gasoline yield measured with a microactivity cracking test is maintained at a high level, but coke and hydrogen yields remain higher than those on an unpoisoned catalyst

ORA - Optical Resonators and Applications - Programme BLANC 2010

National audienceMicrocavités optiques à très haut facteur de qualité : Les microcavités optiques à très haut facteur de qualité sont d'un grand intérêt pour des applications dans des domaines aussi différents que l'optoélectronique, la métrologie ou la physique fondamentale. Ils sont utilisés par exemple pour : le filtrage optique, la commutation tout-optique, l'optique non-linéaire à bas seuil, les sources laser de grande pureté spectrale, les mémoires optiques, les biocapteurs, l'électrodynamique quantique. Méthodes et approches : Dans le projet ORA, nous avons étudié théoriquement et expérimentalement la réalisation de lignes à retard optiques compactes passives ou actives. En parallèle, nous avons étudié la capacité de ces composants à générer directement un signal RF par utilisation de non-linéarité du troisième ordre et/ou des résonateurs actifs dopés Erbium. Après les tests d'évaluation pratiqués nous avons été capables d'intégrer ces composants passifs ou actifs dans des Oscillateurs Opto-Electroniques (OOEs). Le programme présentait deux aspects complémentaires : (i) les micro-résonateurs et leurs systèmes de couplage (ii) les applications et leurs tests de qualification

Dynamical Analysis of Modal Coupling in Rare-Earth Whispering-Gallery-Mode Microlasers

International audienceWe report on an experimental study of a laser regime in erbium-doped whispering-gallery-mode (WGM) microspheres under modal-coupling between the co- and counterpropagating modes. The evidence of modal coupling is observed in the relative intensity noise spectrum of several WGM lasers. Cross-correlation measurements are carried out in order to analyze precisely the emission regimes. It is shown that depending on the material constituting the WGM resonator, frequency-locked bidirectional emission or a self-modulated regime could be reached. The control of the laser emission regime of WGM microlasers is of great importance in the aim of applications in microwave optics or optical sensor miniaturization