Polymerase mutations promoting adaptation of avian influenza virus of subtype H9N2 to mammals

Transmission of influenza viruses from aquatic birds to mammals is promoted by the adaptation of the viral proteins to the new host. This includes the PB2 subunit of the viral polymerase complex. This protein has been described as an important host range factor, able to modulate the virulence of influenza viruses. Several adaptive mutations in the PB2 subunit of various influenza-A subtypes have been described, such as D253N, Q591K, E627K, D701N, S714I and S714R. H9N2 influenza viruses are endemic in poultry in Asia and other parts of the world. Moreover these viruses have been occasionally transmitted to humans and are often involved in the generation of viruses causing zoonotic infections in humans by providing internal genes. H9N2 viruses have therefore the potential to cause a pandemic. This study was undertaken to analyse the role of the PB2 subunit in the adaptation of avian influenza virus of subtype H9N2 to mammals. In the first part of the thesis, the results demonstrated that PB2 mutations D253N, E627K, D701N, S714I and S714R increase the H9N2 polymerase activity in mammalian cells. Furthermore, mutations E627K, D701N and S714I/R also enhance viral growth in mammalian cells. Pathogenicity studies indicated that combination of mutations E627K-D701N-S714R increase the lethality of H9N2 virus in mice. The effects of the adaptive mutations have then been compared in H9N2, H1N1pdm09 and H7N7 viruses. The results have shown that the enhancement of the polymerase activity by the adaptive mutations is higher in the phylogenetically related H9N2 and H7N9 than in the non-related H7N7 and H1N1pdm09 viruses. In addition, analysis of heterologous polymerase complexes composed of H9N2, H1N1pdm09, H7N7, and H7N9 subunits provides further evidence for the concept that this enhancing effect is a specific trait of H9N2-PB2 without significant contribution of PA and PB1. From these observations, it can be concluded that the PB2 subunit of the H9N2 viruses is characterised by a particularly high adaptability to mammalian cells. In the second part of the thesis, the mechanisms by which E627K and D701N promote adaptation to a mammalian host were analysed. The results demonstrated that viruses bearing the avian signature 627E in PB2 are sensitive to RIG-I activation. This sensitivity is mediated by the destabilisation of the nucleocapsid by RIG-I, exposing thereby the double-stranded RNA required for RIG-I activation. In contrast viruses containing mutation E627K interfere with RIG-I activation, by stabilizing the association of the polymerase complex to the nucleocapsid. These observations indicate that PB2 mutation E627K modulates the inhibition of virus replication mediated by RIG-I. Furthermore, the data showed that mutation D701N promotes not only the nuclear import of newly synthesized PB2 protein, but also the nuclear import of PB2 bound to the incoming vRNPs

Étude de la fiabilité opérationnelle des équipements sous pression : applications aux pipelines et aux pompes centrifuges

De nos jours, la demande en équipements sous pression (ESP) a grandement augmenté dans le monde industriel. Ces équipements sont souvent utilisés pour le transport et le stockage des fluides (pétrole, gaz, eau, huile). Dans l'industrie pétrolière et gazière, les pipelines sont parmi les ESP les plus utilisés pour transporter le pétrole, l'essence, les produits chimiques et d'autres fluides sous des pressions et des températures variables. Ces équipements sont fabriqués à partir des matériaux hautes performances conformes aux normes afin d'optimiser leur sécurité et leur fiabilité. En effet, certaines normes et travaux de recherche spécifient des conditions de fonctionnement et des paramètres de conception de canalisations, notamment : taille de fonctionnement optimale, intervalles de sécurité, température pression de fonctionnement nominale (États limites) et pression de rupture. L'objectif principal de ce travail est de développer une approche générique de prédiction des pressions de pré-éclatement d'une série de géométrie de pipelines en acier AISI1020. La prédiction de la pression limite admissible de pré-éclatement est le critère cible de conception des pipelines compte tenu de la géométrie et des propriétés mécaniques de ce matériau. Un modèle d'un pipeline standard générique 3D a été mis en place et développé à l'aide du logiciel commercial Abaqus couplé avec un script Python. La validation des prédictions résultats de la simulation a été faite avec des modèles analytiques et des résultats d'essais d'éclatement expérimentaux. Un plan d'expérience d'essai-calcul est aussi considéré pour l'étude de la partie de décharge d'une pompe centrifuge dont on connait respectivement sa composition et les propriétés mécaniques de son matériau. L'influence des paramètres de conception (épaisseur, niveaux des pressions, propriétés physiques) sur les pressions limites admissibles a été étudiée

Magnetic Behavior of Co/Pt and TbCo Nanocaps Assembly for Bit Pattern Media

Large area patterning of self-assembled alumina nanobumps, with hexagonally close-packed order, has been used to create ordered array of bit pattern magnetic media. We have studied the magnetic properties of perpendicular magnetic TbCo alloy and Co/Pt multilayers deposited on self assembled alumina nanobumps. Measurement of reversal field as a function of field intensity, as well as magnetic force microscopy images confirm the weakness of exchange coupling between bits in the case of Co/Pt multilayer while stronger coupling is observed in the case of TbCo alloys. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3535

Magnetic Behavior of Co/Pt and TbCo Nanocaps Assembly for Bit Pattern Media

Large area patterning of self-assembled alumina nanobumps, with hexagonally close-packed order, has been used to create ordered array of bit pattern magnetic media. We have studied the magnetic properties of perpendicular magnetic TbCo alloy and Co/Pt multilayers deposited on self assembled alumina nanobumps. Measurement of reversal field as a function of field intensity, as well as magnetic force microscopy images confirm the weakness of exchange coupling between bits in the case of Co/Pt multilayer while stronger coupling is observed in the case of TbCo alloys. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3535

Atomically Sharp Interface in an h-BN-epitaxial graphene van der Waals Heterostructure

International audienceStacking various two-dimensional atomic crystals is a feasible approach to creating unique multilayered van der Waals heterostructures with tailored properties. Herein for the first time, we present a controlled preparation of large-area h-BN/graphene heterostructures via a simple chemical deposition of h-BN layers on epitaxial graphene/SiC(0001). Van der Waals forces, which are responsible for the cohesion of the multilayer system, give rise to an abrupt interface without interdiffusion between graphene and h-BN, as shown by X-ray Photoemission Spectroscopy (XPS) and direct observation using scanning and High-Resolution Transmission Electron Microscopy (STEM/HRTEM). The electronic properties of graphene, such as the Dirac cone, remain intact and no significant charge transfer i.e. doping, is observed. These results are supported by Density Functional Theory (DFT) calculations. We demonstrate that the h-BN capped graphene allows the fabrication of vdW heterostructures without altering the electronic properties of graphene

High Electron Mobility in Epitaxial Trilayer Graphene on Off-axis SiC(0001)

International audienceThe van de Waals heterostructure formed by an epitaxial trilayer graphene is of particular interest due to its unique tunable electronic band structure and stacking sequence. However, to date, there has been a lack in the fundamental understanding of the electronic properties of epitaxial trilayer graphene. Here, we investigate the electronic properties of large-area epitaxial trilayer graphene on a 4° off-axis SiC(0001) substrate. Micro-Raman mappings and atomic force microscopy (AFM) confirmed predominantly trilayer on the sample obtained under optimized conditions. We used angle-resolved photoemission spectroscopy (ARPES) and Density Functional Theory (DFT) calculations to study in detail the structure of valence electronic states, in particular the dispersion of π bands in reciprocal space and the exact determination of the number of graphene layers. Using far-infrared magneto-transmission (FIR-MT), we demonstrate, that the electron cyclotron resonance (CR) occurs between Landau levels with a (B)1/2 dependence. The CR line-width is consistent with a high Dirac fermions mobility of ~3000 cm2·V−1·s−1 at 4 K

Large area molybdenum disulphide-epitaxial graphene vertical Van der Waals heterostructures

International audienceTwo-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as epitaxial graphene - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS2-graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS2 layer onto epitaxial graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS2 is maintained in these heterostructures due to the weak van der Waals interaction with epitaxial graphene. A downshift of the Raman 2D band of the graphene, an up shift of the A1g peak of MoS2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS2 as a result of charge transfer from MoS2 to epitaxial graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design

Haemagglutination inhibition and virus microneutralisation serology assays: use of harmonised protocols and biological standards in seasonal influenza serology testing and their impact on inter-laboratory variation and assay correlation: A FLUCOP collaborative study

Introduction: The haemagglutination inhibition assay (HAI) and the virus microneutralisation assay (MN) are long-established methods for quantifying antibodies against influenza viruses. Despite their widespread use, both assays require standardisation to improve inter-laboratory agreement in testing. The FLUCOP consortium aims to develop a toolbox of standardised serology assays for seasonal influenza. Building upon previous collaborative studies to harmonise the HAI, in this study the FLUCOP consortium carried out a head-to-head comparison of harmonised HAI and MN protocols to better understand the relationship between HAI and MN titres, and the impact of assay harmonisation and standardisation on inter-laboratory variability and agreement between these methods. Methods: In this paper, we present two large international collaborative studies testing harmonised HAI and MN protocols across 10 participating laboratories. In the first, we expanded on previously published work, carrying out HAI testing using egg and cell isolated and propagated wild-type (WT) viruses in addition to high-growth reassortants typically used influenza vaccines strains using HAI. In the second we tested two MN protocols: an overnight ELISA-based format and a 3-5 day format, using reassortant viruses and a WT H3N2 cell isolated virus. As serum panels tested in both studies included many overlapping samples, we were able to look at the correlation of HAI and MN titres across different methods and for different influenza subtypes. Results: We showed that the overnight ELISA and 3-5 day MN formats are not comparable, with titre ratios varying across the dynamic range of the assay. However, the ELISA MN and HAI are comparable, and a conversion factor could possibly be calculated. In both studies, the impact of normalising using a study standard was investigated, and we showed that for almost every strain and assay format tested, normalisation significantly reduced inter-laboratory variation, supporting the continued development of antibody standards for seasonal influenza viruses. Normalisation had no impact on the correlation between overnight ELISA and 3-5 day MN formats.publishedVersio

Self Assembly and Properties of C:WO3 Nano-Platelets and C:VO2/V2O5 Triangular Capsules Produced by Laser Solution Photolysis

Laser photolysis of WCl6 in ethanol and a specific mixture of V2O5 and VCl3 in ethanol lead to carbon modified vanadium and tungsten oxides with interesting properties. The presence of graphene’s aromatic rings (from the vibrational frequency of 1,600 cm−1) together with C–C bonding of carbon (from the Raman shift of 1,124 cm−1) present unique optical, vibrational, electronic and structural properties of the intended tungsten trioxide and vanadium dioxide materials. The morphology of these samples shows nano-platelets in WOx samples and, in VOx samples, encapsulated spherical quantum dots in conjunction with fullerenes of VOx. Conductivity studies revealed that the VO2/V2O5 nanostructures are more sensitive to Cl than to the presence of ethanol, whereas the C:WO3 nano-platelets are more sensitive to ethanol than atomic C