The contribution of grain boundary barriers to the electrical conductivity of titanium oxide thin films

Titanium oxide thin films were prepared by reactive magnetron sputtering. The reactive gas pulsing process was implemented to control the oxygen injection in the deposition process and,consequently, to tune the oxygen concentration in the films from pure titanium to stoichiometric TiO2, maintaining a homogeneous in-depth concentration. The electrical conductivity of the films was investigated as a function of the oxygen injection time, the metalloid concentration and temperature, in the range 90–600 K. The curved Arrhenius plots of the conductivity were examined taking into account the grain boundary limited transport model of Werner J. H. Werner Solid State Phenom. 37–38, 213 1994 . The grain barrier heights were found to depend significantly on the oxygen supplied into the deposition process and thus, on the oxygen-to-titanium atomic ratio in the films. The analysis as a function of temperature showed that the conduction mechanism in the coatings was not solely limited by the oxygen-to-titanium atomic ratio, but also by the grain boundary scattering

The contribution of grain boundary barriers to the electrical conductivity of titanium oxide thin films

Titanium oxide thin films were prepared by reactive magnetron sputtering. The reactive gas pulsing process was implemented to control the oxygen injection in the deposition process and,consequently, to tune the oxygen concentration in the films from pure titanium to stoichiometric TiO2, maintaining a homogeneous in-depth concentration. The electrical conductivity of the films was investigated as a function of the oxygen injection time, the metalloid concentration and temperature, in the range 90-600 K. The curved Arrhenius plots of the conductivity were examined taking into account the grain boundary limited transport model of Werner J. H. Werner Solid State Phenom. 37-38, 213 1994 . The grain barrier heights were found to depend significantly on the oxygen supplied into the deposition process and thus, on the oxygen-to-titanium atomic ratio in the films. The analysis as a function of temperature showed that the conduction mechanism in the coatings was not solely limited by the oxygen-to-titanium atomic ratio, but also by the grain boundary scattering

Analyzing perturbations in phyllotaxis of Arabidopsis thaliana

International audienceVascular plants produce new organs at the tip of the stem in a very organized fashion. This patterning process occurs in small groups of stem cells, the so-called shoot apical meristems (SAM), and generates regular patterns called phyllotaxis. The phyllotaxis of the model plant Arabidopsis thaliana follows a Fibonacci spiral, the most frequent phyllotactic pattern found in nature. In this phyllotactic mode, single organs are initiated successively at a divergence angle from the previous organ close to 137.5°, the golden angle. Cytokinins, a class of plant hormones, is involved in the control of phyllotaxis but its role has remained elusive (Vernoux et al., 2010). By analyzing the expression of several cytokinin signaling regulators in the meristem, we found that the pseudo-phosphotransfer protein AHP6 is expressed specifically during early organogenesis (unpublished results). AHP6 has been demonstrated to act as an inhibitor of cytokinin signaling (Mahonen et al., 2006) and we further observed a destabilization of phyllotaxis in ahp6 null mutant. To understand how AHP6 acts in the control of Arabidopsis phyllotaxis, we analyzed sequences of divergence angles in both wild-type and ahp6 mutant plants. We thus measured the divergence angle between successive flowers on a stem from the base (older flowers) to the top (younger flowers)

Identification of viscoplastic parameters and characterization of Lüders behaviour using digital image correlation and the virtual fields method

In this study, tensile loading experiments are performed on notched steel bars at an average applied strain rate of 1s-1. Displacement fields are measured across the specimen by coupling digital image correlation (DIC) with imaging using high speed CCD cameras (4796 fps). Results from the experiments indicate the presence of local strain rates ranging from 0.1 to 10s-1 in the notched specimens. The heterogeneity of the strain rate fields provides suitable conditions for determining simultaneously all the elasto-visco-plastic constitutive parameters governing the material behavior. For that, the whole stress fields are reconstructed in the specimen using the full-field deformation measurements. This reconstruction is repeated with different constitutive parameters until the average stress in the specimen matches the one measured with the load cell response. Perzyna’s model is firstly considered for the reconstruction of stresses but it is shown to be unsuited for providing the drop in the average stress that is systematically detected at the onset of plasticity by the load cell. This drop is attributed to the sudden occurrence of plasticity in the material due to Lüders effect. A modified model for elasto-visco-plasticity taking account of Lüders behavior in the material is considered afterwards. It yields a better agreement between the reconstructed stresses and the load cell response, and a more accurate identification of the parameters driving the visco-plastic model. Eventually, it is shown how to use DIC measurements for replacing the load cell measurements when the transient effects in the test reach the resonance frequency of the load cel

Toward universal forward genetics:Using a draft genome sequence of the nematode oscheius tipulae to identify mutations affecting vulva development

Mapping-by-sequencing has become a standard method to map and identify phenotype-causing mutations in model species. Here, we show that a fragmented draft assembly is sufficient to perform mapping-by-sequencing in nonmodel species. We generated a draft assembly and annotation of the genome of the free-living nematode Oscheius tipulae, a distant relative of the model Caenorhabditis elegans We used this draft to identify the likely causative mutations at the O. tipulae cov-3 locus, which affect vulval development. The cov-3 locus encodes the O. tipulae ortholog of C. elegans mig-13, and we further show that Cel-mig-13 mutants also have an unsuspected vulval-development phenotype. In a virtuous circle, we were able to use the linkage information collected during mutant mapping to improve the genome assembly. These results showcase the promise of genome-enabled forward genetics in nonmodel species

Molecular envelopes derived from protein powder diffraction Molecular envelopes derived from protein powder diffraction data

The preparation of single crystals suitable for X-ray analysis is frequently the most difficult step in structural studies of proteins.With the aid of two examples, it is shown that de novo solution of the crystallographic phase problem can be achieved at low resolution using microcrystalline powder samples via the single isomorphous replacement method. With synchrotron radiation and optimized instrumentation, high-quality powder patterns have been recorded, from which it was possible to generate phase information for structure factors up to 6 A resolution. pH- and radiation-induced anisotropic lattice changes were exploited to reduce the problem of overlapping reflections, which is a major challenge in protein powder diffraction. The resulting data were of sufficient quality to compute molecular envelopes of the protein molecule and to map out the solvent channels in the crystals. The results show that protein powder diffraction can yield low-resolution data that are potentially useful for the characterization of microcrystalline proteins as novel micro- and mesoporous materials as well as for structural studies of biologically important macromolecules

Airway and Esophageal Stenting in Patients with Advanced Esophageal Cancer and Pulmonary Involvement

BACKGROUND: Most inoperable patients with esophageal-advanced cancer (EGC) have a poor prognosis. Esophageal stenting, as part of a palliative therapy management has dramatically improved the quality of live of EGC patients. Airway stenting is generally proposed in case of esophageal stent complication, with a high failure rate. The study was conducted to assess the efficacy and safety of scheduled and non-scheduled airway stenting in case of indicated esophageal stenting for EGC. METHODS AND FINDINGS: The study is an observational study conducted in pulmonary and gastroenterology endoscopy units. Consecutive patients with EGC were referred to endoscopy units. We analyzed the outcome of airway stenting in patients with esophageal stent indication admitted in emergency or with a scheduled intervention. Forty-four patients (58+/-\-8 years of age) with esophageal stenting indication were investigated. Seven patients (group 1) were admitted in emergency due to esophageal stent complication in the airway (4 fistulas, 3 cases with malignant infiltration and compression). Airway stenting failed for 5 patients. Thirty-seven remaining patients had a scheduled stenting procedure (group 2): stent was inserted for 13 patients with tracheal or bronchial malignant infiltration, 12 patients with fistulas, and 12 patients with airway extrinsic compression (preventive indication). Stenting the airway was well tolerated. Life-threatening complications were related to group 1. Overall mean survival was 26+/-10 weeks and was significantly shorter in group 1 (6+/-7.6 weeks) than in group 2 (28+/-11 weeks), p<0.001). Scheduled double stenting significantly improved symptoms (95% at day 7) with a low complication rate (13%), and achieved a specific cancer treatment (84%) in most cases. CONCLUSION: Stenting the airway should always be considered in case of esophageal stent indication. A multidisciplinary approach with initial airway evaluation improved prognosis and decreased airways complications related to esophageal stent. Emergency procedures were rarely efficient in our experience

Noise and Robustness in Phyllotaxis

A striking feature of vascular plants is the regular arrangement of lateral organs on the stem, known as phyllotaxis. The most common phyllotactic patterns can be described using spirals, numbers from the Fibonacci sequence and the golden angle. This rich mathematical structure, along with the experimental reproduction of phyllotactic spirals in physical systems, has led to a view of phyllotaxis focusing on regularity. However all organisms are affected by natural stochastic variability, raising questions about the effect of this variability on phyllotaxis and the achievement of such regular patterns. Here we address these questions theoretically using a dynamical system of interacting sources of inhibitory field. Previous work has shown that phyllotaxis can emerge deterministically from the self-organization of such sources and that inhibition is primarily mediated by the depletion of the plant hormone auxin through polarized transport. We incorporated stochasticity in the model and found three main classes of defects in spiral phyllotaxis – the reversal of the handedness of spirals, the concomitant initiation of organs and the occurrence of distichous angles – and we investigated whether a secondary inhibitory field filters out defects. Our results are consistent with available experimental data and yield a prediction of the main source of stochasticity during organogenesis. Our model can be related to cellular parameters and thus provides a framework for the analysis of phyllotactic mutants at both cellular and tissular levels. We propose that secondary fields associated with organogenesis, such as other biochemical signals or mechanical forces, are important for the robustness of phyllotaxis. More generally, our work sheds light on how a target pattern can be achieved within a noisy background

Viral to metazoan marine plankton nucleotide sequences from the Tara Oceans expedition

A unique collection of oceanic samples was gathered by the Tara Oceans expeditions (2009-2013), targeting plankton organisms ranging from viruses to metazoans, and providing rich environmental context measurements. Thanks to recent advances in the field of genomics, extensive sequencing has been performed for a deep genomic analysis of this huge collection of samples. A strategy based on different approaches, such as metabarcoding, metagenomics, single-cell genomics and metatranscriptomics, has been chosen for analysis of size-fractionated plankton communities. Here, we provide detailed procedures applied for genomic data generation, from nucleic acids extraction to sequence production, and we describe registries of genomics datasets available at the European Nucleotide Archive (ENA, www.ebi.ac.uk/ena). The association of these metadata to the experimental procedures applied for their generation will help the scientific community to access these data and facilitate their analysis. This paper complements other efforts to provide a full description of experiments and open science resources generated from the Tara Oceans project, further extending their value for the study of the world's planktonic ecosystems

Reactive Gas Pulsing Process for Oxynitride Thin Films

An original reactive sputtering method, namely the reactive gas pulsing process (RGPP) was developed for the synthesis of titanium oxynitride thin films. Such a method implements a metallic titanium target DC sputtered, a constant supply of argon and nitrogen gases and a pulsing oxygen mass flow rate, which is periodically controlled versus time. Various period times and different patterns can be generated: rectangle, sine, isosceles triangle, mounting or descending triangle and exponential. Real time measurements of the target potential as well as total sputtering pressure are recorded in order to study the instability phenomena of the process. They are also pertinent diagnostic tools to select the most suitable pulsing patterns required to alternate the process between the nitrided and the oxidized sputtering modes. As a result, alternation is produced for exponential and rectangular patterns. For this latter, the influence of the duty cycle α defined as the ratio of the injection time of oxygen by the pulsing period, on the behaviour of the reactive sputtering process and optical properties of deposited films, is systematically investigated. Finally, the added value brought by the exponential patterns is examined. It is shown that the exponential signal leads to significant improvements of the oxygen injection. The purpose is to introduce the right amount of oxygen so as to poison the titanium target surface without saturating the sputtering atmosphere by oxygen. Thus, the speed of pollution of the target surface appears as an appropriate parameter to better understand the beneficial effect of the exponential shape on the control of the RGPP method