Temperature-dependent Raman scattering of KTa1-xNbxO3 thin films

We report a Raman scattering investigation of KTa1-xNbxO3 (x = 0.35, 0.5) thin films deposited on MgO and LaAlO3 as a function of temperature. The observed phase sequence in the range from 90 K to 720 K is similar to the structural phase transitions of the end-member material KNbO3. Although similar in the phase sequence, the actual temperatures observed for phase transition temperatures are significantly different from those observed in the literature for bulk samples. Namely, the tetragonal (ferroelectric) to cubic (paraelectric) phase transition is up to 50 K higher in the films when compared to bulk samples. This enhanced ferroelectricity is attributed to biaxial strain in the investigated thin films

Influence of some factors on autolysis of Oenococcus oeni

Oenococcus oeni was able to autolyse after transfer to water at 40 degreesC. Cells harvested in the mid-log phase autolyse more rapidly than in other growth phases. Optimum conditions of pH (broad scale,vith two maxima at 4.0 and 7.0) and temperature (40 degreesC) have also been elucidated. Trypsin and EDTA appeared to enhance cell wall autolysis. The activity of several enzymes, namely an amidase or endopeptidase and a N-acetyl-β-D-glucosaminidase, were shown to be involved in the autolytic process, thereby releasing soluble cell wall fragments and nitrogen compounds

Millau viaduct geotechnical studies and foundations

AbstractThe Millau viaduct over the Tarn River is an exceptional bridge considering the height under the deck and the 2.5km total length. Each of the seven high piers is founded on a thick raft setting on four large piles of 5m in diameter and 10–15m deep. The ground schematically consists of limestone in the north and of marls in the south. As the bridge is very sensitive to foundation settlements, the concessionary company decided to use the observational method for controlling the displacements and if necessary stabilize the foundations. The measurements show that the movements have remained small and admissible, particularly in terms of the rotations. The settlements have not occurred continuously under the load, but by steps

Stabilité et renforcement des fronts de taille des tunnels : une approche analytique en contraintes-déformations

National audienceConstruction process of tunnels involve more and more frequently a full face excavation, with high faces. Therefore engineers have to analyse the face stability and to design reinforcement by longitudinal fibreglass bolts. The current methods are mainly based on stability analysis, but they scarcely allow an evaluation of the deformations, except when using numerical modelling, in which the consideration of reinforcements induces very heavy models, much difficult to use in engineering practice. This paper describes a new stress-strain approach, based on a spherical principle, and allowing the calculation of face deformations, including when bolts reinforcement is used. We present the general principles of the methods and its validation, then various parametric analysis, and finally some cases of practical use: evaluation of a safety factor, design of face reinforcement, effect of the confining pressure on the face deformations when using a TBM.Les tunnels sont de plus en plus réalisés en pleine section, ce qui conduit à des hauteurs du front de taille parfois très importantes. C'est pourquoi les ingénieurs sont fréquemment appelés à examiner la tenue du front, et à prévoir son renforcement par des boulons longitudinaux en fibre de verre. Les approches actuelles privilégient les analyses en stabilité, mais ne permettent guère une évaluation des déformations du front, sauf à utiliser des méthodes numériques, dans lesquels la prise en compte des renforcements conduit à des modèles très lourds et peu utilisables en pratique courante. Cet article présente une nouvelle approche analytique en contraintes-déformations, basée sur un principe de symétrie sphérique, et permettant d'évaluer les déformations d'extrusion du front, et ce même lorsque le front est renforcé par des boulons. Nous présentons en premier lieu les principes de la méthode ainsi que sa validation, puis différentes études paramétriques, ainsi que quelques cas possibles d'utilisation : évaluation d'un coefficient de sécurité, dimensionnement d'un renforcement par boulonnage, effet de la pression de confinement sur l'extrusion lors de l'utilisation de boucliers

Current mode monolithic active pixel sensor with correlated double sampling for charged particle detection

A monolithic active pixel sensor operating in current mode for charged particle detection is described. The sensing element in each pixel is an n-well/p-sub diode with a PMOS transistor integrated in an n-well. The drop of the n-well potential from the collection of charge modulates the transistor channel current. Each pixel features two current mode memory cells. The subtraction of distant-in-time samples frees the signal of fixed pattern noise (FPN) and of the correlated low-frequency temporal noise components, resulting in extraction of the particle footprint. The subtraction circuits are placed at each column end. A transimpedance amplifier, integrating in sequence two current samples and subtracting the results in an arithmetic operation, was adopted. The integrated version of the transimpedance amplifier, designed with a maximized conversion gain, is burdened by a risk of an early saturation, imperiling its operation, if the dispersions of the dc current component are too big. The degree of dispersions could not be estimated during the design. Some number of columns is available as a backup with the direct current readout. An external realization of the subtracting circuit, based on the same principle, is used to process direct output columns. The concept of the data acquisition setup developed, the tested performance of an array of cells, and the processing circuitry are described

Youngsters do not pay attention to conversational rules: is this so for nonhuman primates?

The potentiality to find precursors of human language in nonhuman primates is questioned because of differences related to the genetic determinism of human and nonhuman primate acoustic structures. Limiting the debate to production and acoustic plasticity might have led to underestimating parallels between human and nonhuman primates. Adult-young differences concerning vocal usage have been reported in various primate species. A key feature of language is the ability to converse, respecting turn-taking rules. Turn-taking structures some nonhuman primates' adult vocal exchanges, but the development and the cognitive relevancy of this rule have never been investigated in monkeys. Our observations of Campbell's monkeys' spontaneous vocal utterances revealed that juveniles broke the turn-taking rule more often than did experienced adults. Only adults displayed different levels of interest when hearing playbacks of vocal exchanges respecting or not the turn-taking rule. This study strengthens parallels between human conversations and nonhuman primate vocal exchanges

Pulsed laser deposited KNbO3_3 thin films for applications in high frequency range

Potassium niobate thin films were grown by pulsed laser deposition on various substrates. Influence of deposition conditions on film characteristics was studied. Structural investigation evidenced that single phase polycrystalline randomly oriented films were grown on sintered alumina whereas epitaxial films were grown on (100)SrTiO$_3$ and (100)MgO substrates. The microstructure was highly controlled by the structural characteristics. Interdigited capacitors built from KNbO3 films on two different substrates (alumina and MgO) showed the strong influence of the structural characteristics on the dielectric behavior. The variation of the equivalent capacitance measured on the interdigital capacitor on MgO was 6.4% at 2.5 GHz while it was 1.5% on alumina, in both cases for a moderate applied field of $\sim$15 kV cm$^{-1}$. The results show the potentiality of these ferroelectric materials for use in frequency agile microwave electronics