Influence of Ni Catalyst Layer and TiN Diffusion Barrier on Carbon Nanotube Growth Rate

Dense, vertically aligned multiwall carbon nanotubes were synthesized on TiN electrode layers for infrared sensing applications. Microwave plasma-enhanced chemical vapor deposition and Ni catalyst were used for the nanotubes synthesis. The resultant nanotubes were characterized by SEM, AFM, and TEM. Since the length of the nanotubes influences sensor characteristics, we study in details the effects of changing Ni and TiN thickness on the physical properties of the nanotubes. In this paper, we report the observation of a threshold Ni thickness of about 4 nm, when the average CNT growth rate switches from an increasing to a decreasing function of increasing Ni thickness, for a process temperature of 700°C. This behavior is likely related to a transition in the growth mode from a predominantly “base growth” to that of a “tip growth.” For Ni layer greater than 9 nm the growth rate, as well as the CNT diameter, variations become insignificant. We have also observed that a TiN barrier layer appears to favor the growth of thinner CNTs compared to a SiO2 layer

A transposon story : from TE content to TE dynamic invasion of Drosophila genomes using the single-molecule sequencing technology from Oxford Nanopore

International audienceTransposable elements (TEs) are the main components of genomes. However, due to their repetitive nature, they are very difficult to study using data obtained with short-read sequencing technologies. Here, we describe an efficient pipeline to accurately recover TE insertion (TEI) sites and sequences from long reads obtained by Oxford Nanopore Technology (ONT) sequencing. With this pipeline, we could precisely describe the landscapes of the most recent TEIs in wild-type strains of Drosophila 2 melanogaster and Drosophila simulans. Their comparison suggests that this subset of TE sequences is more similar than previously thought in these two species. The chromosome assemblies obtained using this pipeline also allowed recovering piRNA cluster sequences, which was so far impossible using short-read sequencing. Finally, we used our pipeline to analyze ONT sequencing data from a D. melanogaster unstable line in which LTR transposition was derepressed for 73 successive generations. We could rely on single reads to identify new insertions with intact target site duplications. Moreover, the detailed analysis of TEIs in the wild-type strains and the unstable line did not support the trap model claiming that piRNA clusters are hotspots of TE insertions

Correspondance et poésie

Entre la correspondance, écrite au fil de la plume à l’intention d’un destinataire choisi, et la poésie, qui s’adresse a priori à tous au prix d’un travail contre la spontanéité et l’improvisation, les liens pourraient sembler ténus. Mais ces définitions sont par trop restrictives : l’une des caractéristiques de la correspondance est de pouvoir prendre tous les tons et se plier à toutes les formes, à commencer par la poétique. L’épître, ou lettre en vers, en est la manifestation la plus évidente, puisque les deux genres s’y confondent, mais ce n’est pas la seule, loin de là. D’Ovide à Georges Perros en passant par Rimbaud, Verlaine, Louis Ménard et Max Jacob, la première partie de cet ouvrage cherche à définir une « poétique épistolaire » dans l’histoire. Une deuxième partie traite de la dimension régulièrement ludique des lettres accompagnées de vers, semés ou distincts. Ces pratiques communes à l’abbé Cotin, à Nerval, à Verlaine ou à Valéry, peuvent-elles cependant se résumer à de simples « jeux de société » ? Sous le signe des « confidences », une troisième partie distingue d’une part les lettres de poètes (Heredia, Rodenbach, Armand Robin, etc.) à des prosateurs, et d’autre part les lettres de quelques grands prosateurs (Flaubert, Huysmans, Barrès) à des poètes plus ou moins oubliés aujourd’hui (Louise Colet, Adrien Mithouard, Anna de Noailles). Écrites par les meilleurs spécialistes dans leurs disciplines, les dix-neuf études ici rassemblées abordent sous tous les angles, de l’histoire littéraire à la linguistique, tous les types de correspondances (réelles ou fictives, actives ou passives, publiées ou inédites, en vers, en prose, ou les deux), jusqu’aux dédicaces manuscrites d’auteurs sur leurs livres. Elles renouvellent l’interprétation de quelques grands recueils, ainsi que la poétique de la plupart des poètes abordés

Paul Valéry, Cahiers 1894-1914 , vol. XIII

Avec ce volume qui va de mars 1914 à janvier 1915, treizième et dernier tome, s’achève l’édition scientifique sur papier des Cahiers 1894-1914 de Valéry. Le texte questionne l’intelligence, le langage, la musique, le hasard, le rêve, la sensibilité, en des séquences thématiques qui vont de l’aphorisme au petit traité psychologique. Ces cahiers mettent en évidence le retentissement de la Première Guerre mondiale sur le psychisme de Valéry : on y voit le thème et les mots mêmes des premiers vers de La Jeune Parque sortir du choc de la déclaration de guerre

Lessons from a multicentre study of the detectability of viral genomes based on a two-round quality control of GB virus C (GBV-C)/hepatitis G virus (HGV) polymerase chain reaction assay

International audienceThe aim of this study was to determine whether multicentre quality controls for the detectability of viral genomes could contribute to the improvement of diagnostic performance in the participating laboratories. The study was carried out during two successive rounds, during which 18 laboratories specialized in nucleic acid testing analyzed, through a polymerase chain reaction (PCR) assay, a common panel of GB virus C (GBV-C)/hepatitis G virus (HGV) RNA-positive and -negative samples. During the first round, the laboratories used either an 'in-house' PCR procedure or a partly standardized commercial test. After decoding the results of the first round, the procedures of the participating laboratories were compared in order to establish a consensus procedure deduced from those of the laboratories which provided the best results. During the second round, each participating laboratory could use the resulting consensus procedure, or its own procedure, or both. The results of this quality control study indicated that, whatever method used, even specialized and trained laboratories may give false-negative or false-positive results. The commercial assay did not guarantee a systematic high quality level of results. The striking heterogeneity of results observed among laboratories using the same commercial assay confirm that molecular biology methods need skilled technicians. The results of this quality control study suggest that full standardization of viral genome detection, including all steps of the procedure, is necessary and that the laboratories performing PCR should participate in repeated quality control studies, whatever technique is being used

GEMHEP multicenter quality control study of PCR detection of GB virus C/hepatitis G virus RNA in serum

International audiencePCR is, to date, the only available tool for the detection of GB virus C (GBV-C) and hepatitis G virus (HGV) RNAs. Twenty-two French laboratories participated in a quality control study to assess the sensitivity and specificity of their procedures. The panel included 13 positive controls and 7 negative controls. The laboratories used either in-house PCR techniques adapted from the literature or partly standardized commercial tests. Three laboratories performed faultlessly with the entire panel. Most laboratories had excellent specificity (100% in 20 of 22 laboratories). Sensitivity was acceptable (85 to 100%) in 15 centers and insufficient (38 to 77%) in 7. As with nonstandardized in-house PCR, the commercial assays gave discrepant performances in different laboratories. These results suggest that laboratories willing to use PCR for detection of GBV-C/HGV RNA for research or diagnostic purposes should participate in multicenter quality control trials