Lattice thermal conductivity of Bi 2 Te 3 and SnSe using Debye-Callaway and Monte Carlo phonon transport modeling: Application to nanofilms and nanowires

International audienc

Development of microdevices for the in-plane thermoelectric characterization of deposited films

International audienc

High quality epitaxial fluorine-doped SnO2 films by ultrasonic spray pyrolysis: Structural and physical property investigation

Despite its wide use in the display and photovoltaic industries, fluorine-doped tin oxide (F:SnO2, FTO) has been studied only in its polycrystalline form. In this work, we report on the first growth of epitaxial FTO thin film by ultrasonic spray pyrolysis – a simple chemical deposition method – and we reveal the structure-property interplay by investigating in details its growth, morphology and strain/defects. Epitaxial FTO films are successfully grown on (110) rutile TiO2 single crystals and form mosaic domains with an out-of-plane distribution smaller than 0.5°, showing high structural quality comparable to epitaxial films prepared by molecular beam epitaxy and pulsed-laser deposition. Owing to the large lattice mismatch with rutile TiO2, the FTO film develops significant structural defects to release the epitaxial strain and is consequently nearly fully relaxed with a slight residual strain of 0.1–0.2%. With the help of an innovative nano-beam precession electron diffraction technique, the strain distribution is mapped at the TiO2/FTO interface, from which we identify the interfacial and secondary strain relaxation taking place mainly in the first 22 nm in the FTO film. The Hall-mobility of the epitaxial FTO films is close to the state-of-the-art and expected to improve further at lower doping concentrations

Boosting the piezoelectric coefficients of flexible dynamic strain sensors made of chemically-deposited ZnO nanowires using compensatory Sb doping

International audienceThe piezoelectric devices made of ZnO nanowires have received a great interest in the past decade as potential nanogenerators and sensors. However, their characteristics are still limited significantly by the screening of the piezoelectric potential generated under mechanical solicitations, originating from the high density of free electrons in ZnO nanowires. In order to tackle that issue, we develop the compensatory Sb doping of ZnO nanowires grown by chemical bath deposition, both in the low- and high-pH regions using Sb glycolate and ammonia as chemical additives. The adsorption process of Sb(III) species on the positively charged surfaces of ZnO nanowires proceeds through attractive electrostatic forces, resulting in the significant incorporation of Sb dopants with an atomic ratio in the range of 0.11–0.45%. The optical properties of Sb-doped ZnO nanowires exhibit additional phonon modes related to Sb dopants in the range of 500–750 cm-1 in the Raman spectra, and some specific characteristics in the nature and intensity of radiative recombination in the cathodoluminescence spectra. Importantly, the integration of Sb-doped ZnO nanowires encapsulated in PMMA and grown on PDMS into flexible piezoelectric dynamic strain sensors is shown to drastically boost the piezoelectric charge and voltage coefficients by a factor of 2.65 and 1.91, following the significant incorporation of Sb dopants. A subsequent thermal annealing under oxygen atmosphere is revealed to further increase the piezoelectric charge and voltage coefficients by an additional factor of 1.38 and 1.49, following the activation of Sb doping and engineering of hydrogen-related defects. Two figures-of-merit are eventually derived from the piezoelectric charge and voltage coefficients and their values for flexible piezoelectric composites made of annealed Sb-doped ZnO nanowires are compared to more conventional piezoelectric materials, showing their high potential for medical devices. The present findings highlight the strategy consisting in simultaneously introducing compensatory acceptors and engineering hydrogen-related defects to reduce the screening effect, representing an additional powerful way to enhance the characteristics of the piezoelectric devices integrating ZnO nanowires

Tuning the properties of F:SnO 2 (FTO) nanocomposites with S:TiO 2 nanoparticles – promising hazy transparent electrodes for photovoltaics applications

International audienc

An endogenous vitamin K-dependent mechanism regulates cell proliferation in the brain subventricular stem cell niche.

International audienceNeural stem cells (NSC) persist in the adult mammalian brain, within the subventricular zone (SVZ). The endogenous mechanisms underpinning SVZ stem and progenitor cell proliferation are not fully elucidated. Vitamin K-dependent proteins (VKDPs) are mainly secreted factors that were initially discovered as major regulators of blood coagulation. Warfarin ((S(-)-3-acetonylbenzyl)-4-hydroxycoumarin)), a widespread anticoagulant, is a vitamin K antagonist that inhibits the production of functional VKDP. We demonstrate that the suppression of functional VKDPs production, in vitro, by exposure of SVZ cell cultures to warfarin or, in vivo, by its intracerebroventricular injection to mice, leads to a substantial increase in SVZ cell proliferation. We identify the anticoagulant factors, protein S and its structural homolog Gas6, as the two only VKDPs produced by SVZ cells and describe the expression and activation pattern of their Tyro3, Axl, and Mer tyrosine kinase receptors. Both in vitro and in vivo loss of function studies consisting in either Gas6 gene invalidation or in endogenous protein S neutralization, provided evidence for an important novel regulatory role of these two VKDPs in the SVZ neurogenic niche. Specifically, we show that while a loss of Gas6 leads to a reduction in the numbers of stem-like cells and in olfactory bulb neurogenesis, endogenous protein S inhibits SVZ cell proliferation. Our study opens up new perspectives for investigating further the role of vitamin K, VKDPs, and anticoagulants in NSC biology in health and disease

Aflibercept in Combination With FOLFIRI as First-line Chemotherapy in Patients With Metastatic Colorectal Cancer (mCRC): A Phase II Study (FFCD 1302)

International audienc

Electrodeposition of Tin Selenide from Oxalate-Based Aqueous Solution

In this work, we report a study of the electrodeposition of SnSe. Considering the difficulty to stabilize the baths containing Sn(II) and Se(IV) precursors, we investigated the benefits of using sodium oxalate as a complexing agent. Preliminary cyclic voltammetric (CVs) experiments were performed to study the electrochemical behavior of tin and selenium redox systems within this specific electrolyte solution. The study revealed that the oxalate reagent stabilizes the bath chelating Sn(II) and then preventing the precipitation of SnO2. From the CVs, a growth mechanism is proposed and a synthesis potential window is defined, in which the electrodeposition of SnSe films was investigated. Between -0.5 and -0.6 V vs sat. AgCl/Ag, the deposits exhibit typical polycrystalline SnSe needle-like grains. SnSe was shown by Raman spectroscopy and the XRD patterns display an orthorhombic single-phase for this compound. Additional Mössbauer analyses confirm the presence of Sn(II), which is in good agreement with the chemical composition of SnSe films. Moreover, a cross-analysis between the methods shows also the presence of SnSe2 in minor proportion. The depth profile analyses of the samples reveal an in-depth homogeneity as well as the presence of oxygen at the layer surface

Les outils de mesure de la mobilité

Ouvrage diffusé par le Cereq Centre d'études et de recherches sur les qualifications, Marseille 13567 (FRA) ; Collection : Net.Doc (48) ; ISSN 1776-3177 - Information sur la première de couverture : « Ce document est présenté sur le site du Céreq afin de favoriser la diffusion et la discussion de résultats de travaux d’études et de recherches. Il propose un état d’avancement provisoire d’une réflexion pouvant déboucher sur une publication. Les hypothèses et points de vue qu’il expose, de même que sa présentation et son titre, n’engagent pas le Céreq et sont de la responsabilité des auteurs. »National audienceMobilité de cursus, mobilité d’insertion, déterminants de la mobilité, approche quantitative ou qualitative, ce chapitre expose les outils connus pour étudier la mobilité, que ce soit pour les Observatoires de la vie étudiantes (OVE) ou pour les chercheurs qui souhaitent analyser les processus de l’orientation dans l’enseignement supérieur ou les phases d’insertion professionnelle des sortants. Il est organisé en trois parties : les sources statistiques, les nomenclatures, les variables et indicateurs. La première partie cherche à faire le point sur les différentes sources statistiques existantes. Néanmoins, il convient de préciser que, si les données existent, elles ne sont pas nécessairement immédiatement à portée d’études. Certaines, de type institutionnel, demandent d’être dans l’institution, d’autres d’autorisation de mise à disposition, d’extraction des différents champs utiles à l’analyse. Certaines enfin peuvent faire l’objet, à partir d’une source-mère, d’une extension restreinte au domaine d’étude. Il s’agit en outre d’un bilan hic et nunc, sur les sources disponibles et malgré notre souhait de rechercher l’exhaustivité, il s’agit d’un panorama de nos connaissances sur ces mêmes données sans garantie qu’un oubli se soit glissé dans cette description. Il conviendrait alors de nous les signaler. On décrira ces sources selon quatre points : un descriptif des sources et leur approche de la mobilité, leur(s) intérêt(s), leur(s) limite(s) et les interlocuteurs (population visée et destinataires des études). En fin d’article, un tableau résumera les différentes sources. Celles-ci sont abordées selon une approche territoriale, elle-même corrélée à la mobilité : internationale, nationale, régionale et locale. Les deuxième et troisième parties visent à donner les clefs de traitements des sources précédemment présentées. Quelles nomenclatures utiliser ? Sur quelles variables de mobilité faut-il travailler ? Comment construire des indicateurs pertinents permettant de suivre l’évolution de l’attractivité d’un établissement ou d’une formation ? Comment analyser les trajectoires d’insertion professionnelle des sortants ? Autant de questions pour lesquelles nous avons essayé de proposer des réponses simples et pratiques à mettre en oeuvre. En fin d’article, plusieurs pistes nouvelles, encore peu développées à l’heure actuelle, font l’objet d’une présentation succincte