Measurement of gas phase characteristics using amonofibre optical probe in a three-phase flow

The study of gas–liquid–solid systems structure requires reliable measurement tools. In this paper, preliminary results on the potential use of a monofibre optical probe to investigate such flow are presented. This probe, manufactured at LEGI, allows the simultaneous measurement of the gas phase residence time and gas phase velocity. This specificity makes this probe more interesting than classical single tip probes (which measure only the gas residence time) or double tip probes (which are more intrusive). Although extensively used in two-phase gas–liquid, this probe was never used in gas–liquid–solid systems. First, the probe signal response is studied for three-phase flow conditions in the presence of solids. Results show that for soft solids, the probe tips can be contaminated when the probe pierces the solid. The signal processing procedure was modified accordingly to take into account these events. Second, the probe results are validated by comparing global results (global void fraction, gas flowrate) deduced from profile measurements with measurements performed by independent means. Lastly, void fraction profiles and interfacial area are studied more in detail. Depending on the solid loading, these profiles exhibit different behaviours. These features are associated to characteristics of the flow such as the transition from an homogeneous regime to an heterogenous regime, and are consistent with global observation performed by independent means. This demonstrates the ability of the probe to connect local information to the global behaviour and structure of the flow.Fundação para a Ciência e a Tecnologia (FCT

Customization of an optical probe device and validation of a signal processing procedure to study gas-liquid-solid flows. Application to a three-phase internal-loop Gas-lift Bioreactor

The study of local hydrodynamic properties of three-phase bioreactors in biotechnology processes is of great importance, mainly because of the complex interaction between bioreactor and microorganisms. However, classical techniques used for measuring local hydrodynamic properties such as single needle probes are mainly limited to two-phase flows. In this work it was developed and validated a new system, based on the customization of an optical probe initially designed in LEGI. The necessity of a new system was due to the agglomeration of the solid-phase (spent grains which are used as the micro-organisms carrier for the targeted application) around the optical tip, which influences the measurements. This new system allows for the measurement of the main local gas-phase properties in a complex gas-liquid-solid mixture. The new system was first validated for air-water system in an internal loop gas-lift reactor and then applied to a spent grains-air-water mixture at low solid load in an internal gas lift reactor. In addition, experiments using complementary techniques (as high speed camera and PIV) were performed that allowed for the validation of the new system and the explanation of possible physical mechanisms that are underlying on this multiphase system. The system developed has the potential for improvement and use in several biotechnology applications.The authors gratefully acknowledge the financial support from FCT (Fundacao para a Ciencia e Tecnologia, SFRH/BD/37082/2007 and SFRH/BPD/45637/2008)

Front. Plant. Sci.

Plasmodesmata (PD) pores connect neighbouring plant cells and enable direct transport across the cell wall. Understanding the molecular composition of these structures is essential to address their formation and later dynamic regulation. Here we provide a biochemical characterisation of the cell wall co-purified with primary PD of Arabidopsis thaliana cell cultures. To achieve this result we combined subcellular fractionation, polysaccharide analyses and enzymatic fingerprinting approaches. Relative to the rest of the cell wall, specific patterns were observed in the PD fraction. Most xyloglucans, although possibly not abundant as a group, were fucosylated. Homogalacturonans displayed short methylated stretches while rhamnogalacturonan I species were remarkably abundant. Ful l rhamnogalacturonan II forms, highly methyl-acetylated, were also present. We additionally showed that these domains, compared to the broad wall, are less affected by wall modifying activities during a time interval of days. Overall, the protocol and the data presented here open new opportunities for the study of wall polysaccharides associated with PD.Ecole Universitaire de Recherche de Sciences des Plantes de Paris-SaclayThe function of membrane tethering in plant intercellular communicatio

The ABA-Deficiency Suppressor Locus HAS2 Encodes the PPR Protein LOI1/MEF11 Involved in Mitochondrial RNA Editing

The hot ABA-deficiency suppressor2 (has2) mutation increases drought tolerance and the ABA sensitivity of stomata closure and seed germination. Here we report that the HAS2 locus encodes the MITOCHONDRIAL EDITING FACTOR11 (MEF11), also known as LOVASTATIN INSENSITIVE1. has2/mef11 mutants exhibited phenotypes very similar to the ABA-hypersensitive mutant, hai1-1 pp2ca-1 hab1-1 abi1-2, which is impaired in four genes encoding type 2C protein phosphatases (PP2C) that act as upstream negative regulators of the ABA signaling cascade. Like pp2c, mef11 plants were more resistant to progressive water stress and seed germination was more sensitive to paclobutrazol (a gibberellin biosynthesis inhibitor) as well as mannitol and NaCl, compared with the wild-type plants. Phenotypic alterations in mef11 were associated with the lack of editing of transcripts for the mitochondrial cytochrome c maturation FN2 (ccmFN2) gene, which encodes a cytochrome c-heme lyase subunit involved in cytochrome c biogenesis. Although the abundance of electron transfer chain complexes was not affected, their dysfunction could be deduced from increased respiration and altered production of hydrogen peroxide and nitric oxide in mef11 seeds. As minor defects in mitochondrial respiration affect ABA signaling, this suggests an essential role for ABA in mitochondrial retrograde regulation

Action du carbonate de calcium sur la vase d'un étang. I - Essais comparatifs dans l'étang et au laboratoire

Ce travail a pour but de mener in situet au laboratoire des expériences àcaractere quantitatif sur l'action du carbonate de calcium en apport au niveau de l'interface vaseeau de l'étang de Léon. II permet d'observer dans les sédiments l'élévation du pH et des populations microbiennes aérobies en relation avec une sensible diminution des composés organiques. Dans la phase liquide, la mise en évidepce d'une meilleure oxygénation du milieu se trouve liée à une implantation d'algues benthiques dans les vases traitées. Enfin, des analyses menées en fin d'expérience permettent d'évaluer la zone de pénétration du carbonate de calcium dans le sédiment et appellent une étude complémentaire permettant d'apprécier l'action de la craie lorsqu'elle est incorporée, A l'état divisé, dans la vase

Validation d'une méthode qualitative d'estimation de l'influence de la météorologie sur le bruit

We first propose a simple method for helping the acoustician to estimate the effects of meteorological conditions on noise propagation, at least qualitatively. This method is based on a double-entry grid that only requires simple meteorological observations. We then compare the qualitative estimations given by the grid to the results of an outdoor experiment. Human evaluation of climatic conditions is shown to be satisfactory for a qualitative estimation of their effects on noise measurements

Sisfito: um sistema de administração de herbário.

Com o objetivo de subsidiar os trabalhos de identificação do material botânico, está em fase adiantada de concepção, um arquivo de dados complementares inerentes ~s características morfológicas das plantas