Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Evolution des propriétés physico-chimiques de surface des matériaux quasicristallins lors de sollicitations électrochimiques

Ce travail porte sur l'étude d'alliages intermétalliques complexes (alliages quasicristallins et approximants) à base aluminium, de type AI-(Cu)-Fe-Cr. Il s'agit d'étudier et de comparer les propriétés physico-chimiques de surface (composition, structure, réactivité) d'alliages de compositions et de structures variées soumis à des sollicitations électrochimiques en surface (corrosion en milieu électrolytique agressif, vieillissement et oxydation à l'ambiante). L'étude est menée en partenariat avec Saint-Gobain dans le cadre d'une application potentielle de ces alliages sous forme de revêtements d'ustensiles de cuisson. La première phase a consisté à élaborer des alliages massifs AI-(Cu)-Fe-Cr et à les caractériser. Ensuite, nous avons étudié les propriétés de corrosion de ces alliages dans un milieu électrolytique contenant de l'acide citrique et des ions chlorure. Nous avons pu déterminer les différents mécanismes de corrosion mis en jeu et identifier certaines compositions d'alliages particulièrement résistants. Enfin, l'évolution des propriétés de surface sous sollicitation électrochimique a été envisagée. Dans le cadre de l'étude de la résistance à la corrosion, les propriétés de topographie, de composition et de structure des surfaces ont été analysées. Nous avons par ailleurs mis en évidence un phénomène de vieillissement des surfaces à l'ambiante pour des échantillons de type AI-Cr-Fe. Nous avons modélisé la surface de ces matériaux, son évolution en fonction du temps d'exposition à l'air et corrélé ces résultats à la réactivité chimique de surfaceThe main goal of this study is to understand how the surface properties of quasicrystalline and approximant alloys are modified when submitted to various kinds of electrochemical stress. The alloys are Al-based complex intermetallic phases of the AI-(Cu)-Fe-Cr system, submitted to either corrosion test in aggressive media or simply to oxidation and ageing in ambient conditions. ln a first part, bulk alloys of the AI-(Cu)-Fe-Cr system were synthesized and their atomic structure was characterised. Then, the corrosion behaviour of these alloys was investigated with a view to identify the role of the chemical composition and of the crystallographic structure on their ability to resist corrosion attack in a medium containing citric acid and chloride anions. This work bas allowed us to âetermine the corrosion mechanisms and to identify some alloy compositions which demonstrate high-resistance against corrosion. The last part focusses on the evolution of surface structure and chemistry as a function of electrochemical stress. The topography, composition and structure of corroded samples were analysed. ln addition, for AICrFe samples, we have highlighted an ageing phenomenon of the surfaces in ambient conditions. We have proposed a model describing the surface of these materials as a stacking of several layers with different chemistry. The surface ageing is modelled and related to the observed modifications of the chemical reactivity.NANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF

Initial stages of multi-phased aluminium alloys anodizing by MAO: micro-arc conditions and electrochemical behaviour

International audienceThe electrochemical behaviour of AA1050 and AA2214 alloys was studied in a KOH/silicate in order to investigate the first stages of the coating formation during MAO process (by SEM and electrochemical measurements). Before the sparking initiation, occurring around 300 V for both alloys, a thin inner layer of aluminium oxide grows by a classical anodizing mechanism, and induces a great enhancement of the electrochemical resistance. Then, the micro-arc regime beyond 300 V leads to the formation of a dense, thicker but cracked external aluminium oxide layer. Afterwards, from 400 V, a sharp increase of current density named ``current wall'' and due to an increase of oxide conductivity, leads to a significant oxygen release and the occurrence of large and energetic sparks. Microscopic analyses reveal that the presence of copper-rich intermetallic phases in the multi-phased alloy (AA2214) induces the incorporation of copper nanoparticles in the gamma-alumina layer formed by the sparking phenomenon. These copper particles increase the reaction of water oxidation during the classical anodizing stage, and result in a delay of the sparking initiation during the galvanostatic anodizing and in a lower electrochemical resistance of the anodized layers

Micro-arc oxidation of AZ91 Mg alloy: An in-situ electrochemical study

International audienceThe growth of coatings by micro-arc oxidation is based on the formation of spark discharges appearing at the metal/electrolyte interface over the dielectric breakdown potential. On Mg and Mg alloys, this anodizing process is usually performed in alkaline electrolytic bathes in which fluorides or silicates are added. In concentrated KOH electrolytes, in-situ electrochemical impedance spectroscopy measurements are performed at high voltage (up to 80 V) and show that the dielectric breakdown occurs for a threshold capacitance at the electrochemical interface. The main positive role of fluorides and silicates in both the reinforcement of the resisting properties of the coating and its further growth under spark effect is highlighted

Electrochemical behavior of zinc in KOH media at high voltage: Micro-arc oxidation of zinc

International audienceElectrochemical behavior of pure zinc was studied in alkaline KOH-based media over a large range of voltage (0-300 V) in order to investigate the occurrence of the micro-arc phenomenon, responsible for the formation of ``ceramic-like'' oxide layer. According to electrolyte composition, three anodizing steps can be observed, first, a classical anodizing process at low voltage, a voltage range of micro-arc phenomenon with a more or less intense water oxidation, and a sharp current rise corresponding to an increase of electronic conductivity of ``metal/oxide/electrolyte'' interface. Both KOH concentration and presence of additives in the electrolytic bath control the micro-arc voltage range, and the composition of anodized layer. Nevertheless, the internal layer of the coating remains mainly constituted by crystallized ZnO, formed by a mechanism of solid-state diffusion of O2- under electric field. Despite the significant coating thickness (several microns), the electrochemical characterization of the corrosion behavior in NaCl electrolyte only shows a slight improvement of the performances of the zinc anodized in presence of additives in KOH electrolyte, compared to an untreated one

Corrosion behavior of AZ91 Mg alloy anodized by low-energy micro-arc oxidation: Effect of aluminates and silicates

International audienceAZ91 Mg alloy was anodized by micro-arc oxidation under a low constant current density (10 mA cm(-2)) in an electrolytic bath containing KOH 3M + KF 0.5M + Na3PO4 center dot 12H(2)O 0.25 M. The effects of the anodizing process duration and the presence of aluminate (NaAlO2 0.2 M) or silicate (Na2SiO3 center dot 9H(2)O 0.2 M) as additives were investigated. In terms of corrosion resistance, electrochemical methods (namely, potentiodynamic scans and chronoamperometric measurements) corroborate the results of salt spray test and show that the resistance to pitting corrosion of the treated pieces is not systematically improved by a thicker anodized layer. Actually, the composition of the protective coating is the key factor: the best resistance is obtained in the presence of silicate, which plays the role of self-healing agents in corrosive conditions, whereas the incorporation of aluminate in the oxide has a very weak effect on the corrosion resistance of the treated alloy

Initial stages of AZ91 Mg alloy micro-arc anodizing: Growth mechanisms and effect on the corrosion resistance

10th International Symposium on Electrochemical Methods in Corrosion Research (EMCR), Maragogi, BRAZIL, NOV 18-23, 2012International audienceIn the framework of the new ecological regulations, micro-arc oxidation (MAO) appears as an alternative to usual processes in the field of corrosion protection of Mg alloys. In this work, the initial stages of anodic layer growth in KOH-based electrolytes are studied up to and beyond the initiation of the micro-arc regime. The properties of the first anodized film preceding the occurrence of the dielectric breakdown (corresponding to the start of the micro-arc regime) are mainly determined by the incorporation of additives (fluorides or silicates) in the film, as shown by in situ electrochemical measurements. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and micro-Raman spectroscopy reveal both the change of morphology and chemical state of silicate and fluoride in the anodized layer before and after the micro-arc regime. In terms of electrochemical behaviour, investigated by stationary methods and electrochemical impedance spectroscopy (EIS) in reference corrosive water, the anodic film grown in the silicate medium provides the best corrosion resistance thanks to a thick layer containing Mg2SiO4, whose degradation products seal the porosities of the coating

Electrochemical behaviour of titanium in KOH at high potential

International audienceElectrochemical behaviour of pure titanium was studied in KOH-based media over a large voltage range (0-700 V) in order to understand the micro-arc phenomenon occurrence, leading to the formation of a “ceramic-like” oxide layer. The influence of various KOH concentrations in the electrolytic bath (from 0.01 to 0.2 M) was investigated on titanium substrate by a potentiodynamic scan. Whatever the concentration, the electrochemical behaviour of titanium in KOH media can be described in three steps according to voltage: i) a “conventional anodizing” step controlled by the solid-state diffusion of O2− and Ti4+ ions under the electric field effect, ii) a voltage range during which the micro-arc phenomenon occurs, named “micro-arc region”, iii) a “sharp current rise” induced by the increase of oxide conductivity. After anodizing in galvanostatic conditions, XRD and EDS analyses combined with SEM observations show that all samples have similar morphology with a dense internal layer and a porous external one, constituted by titanium dioxide under anatase and rutile crystallized forms. The electrochemical behaviour of anodized layers was investigated by electrochemical impedance spectroscopy measurements. A Mott-Schottky analysis reveals a n-type semi-conducting behaviour of the oxide layers with a very high donor concentration between 1022 and 1023 cm−3

New zinc-rare earth alloys: Influence of intermetallic compounds on the corrosion resistance

International audienceNew ZnRE 1-2 wt.% alloys (RE = Ce, La and Mischmetal) were synthesized. Microstructural analyses reveal that rare-earth metals are exclusively present in intermetallic phases contained within the zinc matrix: CeZn11 or LaZn13 in binary alloys; Ce1-xLaxZn11 and CeyLa1-yZn13 in Zn-Mischmetal alloys. This phase equilibrium is confirmed by a thermodynamic description of the Zn-rich corner of Zn-Ce-La system. Both intermetallic phases CeZn11 and LaZn13 induce a cathodic inhibition of the corrosion of the ZnRE alloys in comparison with pure zinc. In the specific case of cerium addition, a significant anodic inhibition is also observed

Oxide Growth Mechanism on Mg AZ91 Alloy by Anodizing: Combination of Electrochemical and Ellipsometric In-Situ Measurements

International audienceThe sparking initiation during the anodizing of metals in passivating electrolytic media is highly dependent on the physico-chemical properties of the evolving dielectric interface. The present paper focuses on magnesium alloy AZ91 and describes its anodizing in KOH 3 M over the potential range 0 to 40 V by combining in situ ellipsometric and electrochemical methods. In a first step, a thin and compact MgO anodic film is formed by ionic migration with a rate of 0.4 nm V−1. At 4 V to 5 V, the growth stresses lead to a sharp cracking of this MgO layer and the precipitation of a porous external Mg(OH)2 layer. Under this overlayer acting as a membrane, a defective MgO film grows with a higher growth rate (1.1 nm V−1), inducing a new passivation state. This inner MgO layer is characterized by a relatively high dielectric constant and a large thickness (100 nm at 40 V) and is probably responsible for the low dielectric breakdown voltage observed during the anodizing process of magnesium alloy