Operational experience with a CID camera system

In future high intensity, high energy accelerators particle losses must be minimized as activation of the vacuum chambers or other components makes maintenance and upgrade work time consuming and costly. It is imperative to have a clear understanding of the mechanisms that can lead to halo formation, and to have the possibility to test available theoretical models with an adequate experimental setup. Measurements based on optical transition radiation (OTR) provide an interesting opportunity for analyzing the transverse beam profile due to the fast time response and very good linearity of the signal with respect to the beam intensity. On the other hand, the dynamic range of typical acquisition systems as they are used in the CLIC test facility (CTF3) is typically limited and must be improved before these systems can be applied to halo measurements. One possibility for high dynamic range measurements is an innovative camera system based on charge injection device (CID) technology. With possible future measurements in CTF3 in mind, comparative measurements performed with this innovative camera system, a standard CCD camera and a step-by-step measurement technique based on a small photomultiplier are summarized with emphasi

Characterization of a GDP-Fucose Transporter and a Fucosyltransferase Involved in the Fucosylation of Glycoproteins in the Diatom Phaeodactylum tricornutum

Although Phaeodactylum tricornutum is gaining importance in plant molecular farming for the production of high-value molecules such as monoclonal antibodies, little is currently known about key cell metabolism occurring in this diatom such as protein glycosylation. For example, incorporation of fucose residues in the glycans N-linked to protein in P. tricornutum is questionable. Indeed, such epitope has previously been found on N-glycans of endogenous glycoproteins in P. tricornutum. Meanwhile, the potential immunogenicity of the α(1,3)-fucose epitope present on plant-derived biopharmaceuticals is still a matter of debate. In this paper, we have studied molecular actors potentially involved in the fucosylation of the glycoproteins in P. tricornutum. Based on sequence similarities, we have identified a putative P. tricornutum GDP-L-fucose transporter and three fucosyltransferase (FuT) candidates. The putative P. tricornutum GDP-L-fucose transporter coding sequence was expressed in the Chinese Hamster Ovary (CHO)-gmt5 mutant lacking its endogenous GDP-L-fucose transporter activity. We show that the P. tricornutum transporter is able to rescue the fucosylation of proteins in this CHO-gmt5 mutant cell line, thus demonstrating the functional activity of the diatom transporter and its appropriate Golgi localization. In addition, we overexpressed one of the three FuT candidates, namely the FuT54599, in P. tricornutum and investigated its localization within Golgi stacks of the diatom. Our findings show that overexpression of the FuT54599 leads to a significant increase of the α(1,3)-fucosylation of the diatom endogenous glycoproteins

A study of inclusion behaviour during electroslag remelting

Different mechanisms are proposed in the literature to describe the formation and behaviour of inclusions during electroslag remelting: - dissolution in the liquid metal of the inclusions already present in the electrode and then renucleation in the freezing ingot. - total or partial dissolution in the slag. - exchange reactions between inclusions in the metal and the slag. - entrapment in the freezing ingot of pieces of slag skin or droplets of slag. The mechanism of dissolution of alumina inclusions in a 70/30 CaF₂/Al₂0₃ slag has been studied in detail. For this a new equilibrium diagram for the system CaF₂/Al₂0₃ has been proposed and the diffusion coefficient of alumina in the slag has been determined by the rotating disk system. In a 70/30 CaF₂/Al₂0₃ slag at 1518°C the diffusion coefficient was estimated as D = 8.5 10⁻⁹ m² sec⁻¹. Calculations of the extent of the dissolution of alumina particles in the slag predicted that big particles (800 μ) might dissolve only partially in the slag. Particles of this size were introduced artificially in electrodes, but after electroslag remelting a much larger number of relatively small (15 μ max) alumina, iron aluminates and iron oxide inclusions were found in the ingot. The same types of inclusions could also be observed in ingots obtained after remelting a Ferro Vac-E electrode. The presence of these inclusions cannot be explained by one the mechanisms proposed precedently (dissolution in the liquid metal and then renucleation or partial dissolution in the slag), but only by an electrolytic oxidation and electrolytic aluminum dissolution on the electrodes and then nucleation of deoxidation products in the freezing ingot.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat

Formation of Bimetallic Nanoparticle Arrays and Evidence for their Stability at High Temperature under Gas Pressure in the Environmental TEM

International audienc

Formation of Bimetallic Nanoparticle Arrays and Evidence for their Stability at High Temperature under Gas Pressure in the Environmental TEM - VIRTUAL

MICROSCOPIE+MEME+EEH:FCA:LBU:TEPInternational audienceSupported catalysts are generally composed of, at least, one nanometric active phase deposited and/or synthesized at the surface of a convenient nanometer/micrometer powder support. As such these are rather complex systems with many variable parameters: dispersion on the support, size distribution, morphology, structure, defects, variable chemical phases, variable exposed facets of the active phases, interaction with the support, etc. It is thus quite cumbersome to correlate a catalytic behavior with specific physicochemical properties. The synthesis of nanometric particles (NPs) with well controlled characteristics is thus crucial to better understand the behavior of the active phase during reaction and to better correlate its behavior with its catalytic performance. The di-block copolymer approach is well suited to obtain well controlled (size, ordered arrays) supported NPs which can be used as supported metallic catalysts on both flat (model catalysts) and powder (realistic catalysts) supports [1]. In this approach, an amphiphilic di-block copolymer dissolved in toluene yields a system of inverse micelles. We can then metallize the core of these micelles by introducing metal salts. Such systems can then be deposited on flat surfaces by dip or spin coating for instance. We have already extended this method to the synthesis of bimetallic model catalysts [2]. However, many questions are still open concerning, for instance, the formation of unique NPs at the core from the pre-formed bimetallic seeds (Fig. 1b-d) or the stability of the arrays of bimetallic NPs (Fig. 1a) with increasing temperature in presence of reactive gases.In order to gain insight on such issues we have used an Environmental TEM (Titan ETEM G2 from FEI/ThermoFisher Scientific) operated at 300kV under gas pressures up to 20 mbar. To vary the temperature, we have used a WildFire support holder with dedicated heating microchips (DENS Solutions) capable of reaching temperatures up to 1300°C. On top of the latter an Au-rich AuPd core-metallized PS-b-P2VP micellar solution was deposited by spin-coating. Special care was taken to minimize/prevent any influence of the electron beam on the observed events; for instance, a new area was systematically used before each increasing step in temperature (Fig. 2). Temperature treatment under oxygen is crucial both to achieve the formation of unique NPs on the micellar core and to eliminate the copolymer. We could see that the seeds within the micellar cores begin to sinter at around 350°C (consistent with the temperature at which the polymers are decomposed and gasified) and the unique NPs are obtained at around 500°C (Fig. 2). The network is remarkably stable above 500°C and up to 800/900°C (Figure 3); around 1000°C, when the temperature approaches the melting temperature of Au (1064°C), the NPs begin to decompose (Fig. 3). These observations clearly open the possibility of using these structures under rather extreme catalytic conditions (and thus widens the range of catalytic applications); the stability of the arrays appears to be (only) dependent on the intrinsic properties of the metals used [3].References:[1] B Roldan Cuenya, Accounts of Chemical Research 46 (2013) 1682.[2] E Ehret et al, Nanoscale 7 (2015) 13239.[3] The authors acknowledge the French Microscopy and Atom probe network (METSA) and the Consortium Lyon – St-Etienne de Microscopie (CLYM) for supporting this work

Diatom-Specific Oligosaccharide and Polysaccharide Structures Help to Unravel Biosynthetic Capabilities in Diatoms

International audienceDiatoms are marine organisms that represent one of the most important sources of biomass in the ocean, accounting for about 40% of marine primary production, and in the biosphere, contributing up to 20% of global CO2 fixation. There has been a recent surge in developing the use of diatoms as a source of bioactive compounds in the food and cosmetic industries. In addition, the potential of diatoms such as Phaeodactylum tricornutum as cell factories for the production of biopharmaceuticals is currently under evaluation. These biotechnological applications require a comprehensive understanding of the sugar biosynthesis pathways that operate in diatoms. Here, we review diatom glycan and polysaccharide structures, thus revealing their sugar biosynthesis capabilities

An experimental and analytical study of the elasticity of model polyurethane networks crosslinked by tri- and quadriisocyanate

The original publication is available at www.springerlink.com : http://link.springer.com/article/10.1007%2Fs00396-009-2145-6?LI=truePolyurethane networks have been prepared from a mix of tri- and quadriisocyanate and from two types of diols, polyether-based (with molar masses of 1,000, 2,000, and 4,000 g/mol) and polyester-based (1,035 g/mol). The weight fraction of sol has been measured, as well as the elastic shear modulus of the gels. It has been found that the statistical theory of network formation predicts a weight fraction of sol in agreement with the experimental results, but its standard combination with the theory of rubber elasticity disagrees significantly with the elastic modulus measured. This suggests a discrepancy between theory and experiment in terms of elastically active chains. In contrast, the assumption that all nodes in the gel, or even in the system, are elastically active gives much better predictions for the system considered.ANR JCJC MELA

Réalisations phares en microscopie des colonies bactériennes en matrices fromagères

Contexte de l’étude : Les bactéries jouent un rôle clé dans l’affinage et la flaveur du fromage et se développent en colonies.Questions : Quels sont les outils et les méthodes les mieux adaptés en microscopie pour observer les interfaces entre colonie de bactéries (Lactococcus Lactis (coque de 1μm de diamètre)) et matrice solide ainsi que l’organisation des bactéries dans les colonies

Impacts à long terme de changements de pratiques culturales sur le lessivage du nitrate

National audienc