Geodetic tools for hydrogeological surveys: 3D-displacements above a fractured aquifer from GPS time series

International audienceDeep porous reservoirs are subject to charge and discharge of fluids (oil, gas or water), either naturally or induced by human exploitation. This leads to a variation in pressure inside the reservoir and consequently to a deformation of the overlying material. The knowledge of the ground surface displacements allows inferring the fluid migrations and the hydromechanical properties in the porous reservoir. Different kinds of geodetic tools are able to measure this ground deformation: GPS, radar interferometry InSAR, tiltmeters or leveling. Each of them has its own spatial and time characteristics and accuracies that conduct to different kind of applications. After a review of the geodetic studies applied to hydrogeological processes, we describe two examples of GPS time series measurements above the granitic fractured aquifer of Ploemeur, located in French Brittany. These time series records the 3D-displacements induced by the sum of different processes. In this site, the involved processes are mainly the ground deformation related to piezometric level variations in the aquifer that we are looking for and the ocean tide loading that can reach several centimeters in the study area. We present the protocol of the GPS data survey and the processing strategy applied to extract the effect of hydrogeological process with sufficient accuracy. Two different experiments were studied: the long term deformation corresponding to seasonal hydrological cycle and the short term deformation associated to a pumping test. For a same variation in piezometric levels, the vertical ground displacements show larger amplitude for long term signal than for short one, indicating a behavior depending on the duration of the hydrogeological load. This difference of reactivity in time can be related to the heterogeneity of the studied aquifer. Finally, this work shows that geodetic measurements provide important constraints for characterizing aquifer-system response

Structural pattern of the Saïss basin and Tabular Middle Atlas in northern Morocco: hydrological implications

International audienceThe plain of Saïss is a fertile area of great agricultural production with major economic interests. Therefore, the improved knowledge about the water supply is imperative within a context of recurrent droughts and overexploitation of the groundwater. This plain is located in the Meknes-Fes basin and between two deformed domains: the Rif and Middle Atlas. The aquifers are fed by water coming from the Tabular Middle Atlas, for which the pathways are poorly constrained. This study provides new data to determine the water pathways based on a structural map produced from a novel analysis of SPOT images and a digital elevation model. This structural map reveals two fracture sets trending NE-SW and NW-SE. The first set is well known and corresponds to a main trend that controlled the tectonic and stratigraphic evolution of the study area. On the other hand, the NW-SE set was poorly described until now: it is both diffuse and widespread on the Tabular Middle Atlas. A comparison between the regional water flow trend, drainage pattern and structural map shows that the NW-SE fractures control the water flow from the Tabular Middle Atlas to the Saïss plain. A hydrological model is discussed where the water flow is confined onto Liassic carbonates and driven by NW-SE fractures. This study explains how a detailed structural mapping shows hydrology constraints

Optimisation of cancer drug treatments using cell population dynamics

International audienceCancer is primarily a disease of the physiological control on cell population proliferation. Tissue proliferation relies on the cell division cycle: one cell becomes two after a sequence of molecular events that are physiologically controlled at each step of the cycle at so-called checkpoints, in particular at transitions between phases of the cycle [105]. Tissue proliferation is the main physiological process occurring in development and later in maintaining the permanence of the organism in adults, at that late stage mainly in fast renewing tissues such as bone marrow, gut and skin

First Study of the Pyrolysis of a Halogenated Ester: Methyl Chloroacetate

International audienceThe pyrolysis of a halogenated ester, methyl chloroacetate (MC), under dilute atmosphere and quasi-atmospheric pressure was studied at temperatures from 473 to 1048 K using an alumina tubular reactor. MC was chosen as a surrogate to model the thermal decomposition of ethyl bromoacetate, a chemical warfare agent. A maximum MC conversion of 99.8% was observed at a residence time of 2 s, a temperature of 1048 K, and an inlet mole fraction of 0.01. The following products were quantified: CO, CO2, HCl, methane, ethylene, ethane, propene, chloromethane, dichloromethane, vinyl chloride, chloroethane, and dichloroethane. For the first time, a detailed kinetic model of MC pyrolysis was developed and gave a good prediction of the global reactivity and the formation of most of the major products. Flow rate and sensitivity analyses were made to highlight the different pathways of decomposition during the MC pyrolysis. In a first attempt to extrapolate the results obtained with methyl chloroacetate to ethyl bromoacetate, simulations were run with a modified version of the model developed in this study taking into account the differences in bond dissociation energies induced by the change of the chlorine atom by a bromine one

Endothéline-1, angiotensine II et cancer

L’endothéline-1 (ET-1) et l’angiotensine II (AngII) sont des peptides vasoactifs, mais aussi mitogènes et pro-angiogéniques. Tous deux exercent leurs actions par l’intermédiaire de récepteurs couplés aux protéines G : ETA-R et ETB-R pour ET-1 ; AT1R et AT2R pour AngII. L’expression des composants des systèmes ET-1 et AngII dans diverses tumeurs présente généralement une ou plusieurs des caractéristiques suivantes : surexpression du peptide et/ou du récepteur, modification du sous-type de récepteur exprimé et localisation nucléaire du récepteur. ET-1 et AngII agissent sur les différentes étapes de la progression tumorale, et l’utilisation d’antagonistes spécifiques de leurs récepteurs, ou d’inhibiteurs de leur synthèse, est efficace pour ralentir la croissance tumorale in vitro et in vivo dans différents modèles animaux. Des essais cliniques utilisant des antagonistes d’ETA-R donnent des résultats encourageants pour le traitement antitumoral, et une approche similaire ayant pour objectif de bloquer ETB-R ou AT1R est envisageable. De plus, une thérapie combinée ciblant les deux systèmes, ET-1 et AngII, pourrait se révéler bénéfique pour le traitement de tumeurs fortement angiogéniques.Endothelin-1 (ET-1) and angiotensin II (AngII), two potent vasoactive peptides involved in the regulation of cardiovascular homeostasis, also induce mitogenic and pro-angiogenic responses in vitro and in vivo. Both peptides are produced by cleavage of inactive precursors by metalloproteases (endothelin-converting enzyme and angiotensin-converting enzyme, respectively) and activate two subtypes of membrane receptors (ETA-R and ETB-R for ET-1, AT1R and AT2R for AngII) that all belong to the superfamily of G-protein coupled receptors. There is increasing evidence that ETA-R, ETB-R and AT1R are expressed in a variety of cancer cells and tissues, and may play a role on tumor growth, angiogenesis and invasion in vivo. This review summarizes the similarities and differences between the ET-1 and AngII systems with regard to their reported effects on various aspects of cancer. In addition to being expressed on vascular endothelium, ET-1 and AngII receptors participate in tumor angiogenesis through the production of the angiogenic factor VEGF. Furthermore, recent clinical studies indicate that a selective ETA-R antagonist has beneficial effects in prostate cancer, suggesting that a similar approach using ETB-R and AT1R blockers might be envisioned. Experimental data presented here suggest that a combined therapy targeting both ET-1 and AngII systems may prove valuable for future treatments of highly angiogenic tumors

The role of chemistry in the oscillating combustion of hydrocarbons : an experimental and theoretical study

The stable operation of low-temperature combustion processes is an open challenge, due to the presence of undesired deviations from steady-state conditions: among them, oscillatory behaviors have been raising significant interest. In this work, the establishment of limit cycles during the combustion of hydrocarbons in a wellstirred reactor was analyzed to investigate the role of chemistry in such phenomena. An experimental investigation of methane oxidation in dilute conditions was carried out, thus creating quasi-isothermal conditions and decoupling kinetic effects from thermal ones. The transient evolution of the mole fractions of the major species was obtained for different dilution levels (0.0025 <= X-CH4 <= 0.025), inlet temperatures (1080K <= T <= 1190K) and equivalence ratios (0.75 <= Phi <= 1). Rate of production analysis and sensitivity analysis on a fundamental kinetic model allowed to identify the role of the dominating recombination reactions, first driving ignition, then causing extinction. A bifurcation analysis provided further insight in the major role of these reactions for the reactor stability. One-parameter continuation allowed to identify a temperature range where a single, unstable solution exists, and where oscillations were actually observed. Multiple unstable states were identified below the upper branch, where the stable (cold) solution is preferred. The role of recombination reactions in determining the width of the unstable region could be captured, and bifurcation analysis showed that, by decreasing their strength, the unstable range was progressively reduced, up to the full disappearance of oscillations. This affected also the oxidation of heavier hydrocarbons, like ethylene. Finally, less dilute conditions were analyzed using propane as fuel: the coupling with heat exchange resulted in multiple Hopf Bifurcations, with the consequent formation of intermediate, stable regions within the instability range in agreement with the experimental observations

Lutte contre l’échec et nouvelles formes de travail scolaire : le cas d’un établissement de la banlieue genevoise

La lutte contre l’échec a été et reste un puissant levier de questionnement et d’évolution des formes de travail scolaire, sans que l’on puisse opposer l’intention de réformer pour mieux faire, et celle de conserver l’organisation existante en l’explicitant aux élèves afin qu’ils puissent mieux en profiter. Nous présentons et analysons ici le travail et le renouvellement de l’organisation du travail pédagogique tels qu’ils ont été pensés et pratiqués durant 15 ans par une école élémentaire d’un quartier populaire de la périphérie de la ville de Genève. Dans le cadre, puis en marge d’une réforme voulant introduire des cycles d’apprentissage pluriannuels à la place du redoublement des degrés, l’équipe enseignante du Bachet et des chercheurs-partenaires ont petit à petit (et collégialement) élaboré une organisation modulaire des apprentissages de base, fondée sur une hiérarchisation des objectifs et une prise en compte des besoins singuliers des élèves. Après une brève présentation du contexte politique et du cadre théorique de cette recherche-action, nous montrerons comment et pour quelles raisons les formes du travail scolaire ont progressivement évolué dans l’école. Nous présenterons ensuite les questions que se posent les enseignantes au moment où le contrôle politique sur l’instruction publique se resserre, et où l’équipe a le sentiment que son autonomie et le sens de son travail pourraient lui échapper en partie.The fight against school failure has been and still is a powerful tool for questioning and reshaping forms of school work, without opposing the intention to reform in order to do better and the intention to maintain the existing organization, while making it explicit to the students so that they can take advantage of it. We present and analyze the work and the renewal of the organization of teaching activity as they were conceived and practiced during fifteen years by an elementary school in a popular neighbourhood in the suburbs of the city of Geneva. In the framework of, and then in the margin of a reform aiming at introducing multi-year learning cycles instead of repeating classes, the teaching staff of Bachet and some partners researchers has gradually (and collectively) developed a modular organization of basic learning, based on a hierarchy of objectives et taking into account the unique needs of students. After a brief presentation of the political context and the theoretical framework of the research-action, we will demonstrate how and why the forms of school activities have progressively evolved in this school. We will then present the questions raised by the teachers in an era of increasing political control over public education, when teachers have the feeling that their autonomy and the meaning of their work might partly escape them

Evolutionary conservation of P-selectin glycoprotein ligand-1 primary structure and function

<p>Abstract</p> <p>Background</p> <p>P-selectin glycoprotein ligand-1 (PSGL-1) plays a critical role in recruiting leukocytes in inflammatory lesions by mediating leukocyte rolling on selectins. Core-2 O-glycosylation of a <it>N</it>-terminal threonine and sulfation of at least one tyrosine residue of PSGL-1 are required for L- and P-selectin binding. Little information is available on the intra- and inter-species evolution of PSGL-1 primary structure. In addition, the evolutionary conservation of selectin binding site on PSGL-1 has not been previously examined in detail. Therefore, we performed multiple sequence alignment of PSGL-1 amino acid sequences of 14 mammals (human, chimpanzee, rhesus monkey, bovine, pig, rat, tree-shrew, bushbaby, mouse, bat, horse, cat, sheep and dog) and examined mammalian PSGL-1 interactions with human selectins.</p> <p>Results</p> <p>A signal peptide was predicted in each sequence and a propeptide cleavage site was found in 9/14 species. PSGL-1 <it>N</it>-terminus is poorly conserved. However, each species exhibits at least one tyrosine sulfation site and, except in horse and dog, a T [D/E]PP [D/E] motif associated to the core-2 <it>O</it>-glycosylation of a <it>N</it>-terminal threonine. A mucin-like domain of 250–280 amino acids long was disclosed in all studied species. It lies between the conserved <it>N</it>-terminal <it>O</it>-glycosylated threonine (Thr-57 in human) and the transmembrane domain, and contains a central region exhibiting a variable number of decameric repeats (DR). Interspecies and intraspecies polymorphisms were observed. Transmembrane and cytoplasmic domain sequences are well conserved. The moesin binding residues that serve as adaptor between PSGL-1 and Syk, and are involved in regulating PSGL-1-dependent rolling on P-selectin are perfectly conserved in all analyzed mammalian sequences. Despite a poor conservation of PSGL-1 <it>N</it>-terminal sequence, CHO cells co-expressing human glycosyltransferases and human, bovine, pig or rat PSGL-1 efficiently rolled on human L- or P-selectin. By contrast, pig or rat neutrophils were much less efficiently recruited than human or bovine neutrophils on human selectins. Horse PSGL-1, glycosylated by human or equine glycosyltransferases, did not interact with P-selectin. In all five species, tyrosine sulfation of PSGL-1 was required for selectin binding.</p> <p>Conclusion</p> <p>These observations show that PSGL-1 amino acid sequence of the transmembrane and cytoplasmic domains are well conserved and that, despite a poor conservation of PSGL-1 <it>N</it>-terminus, L- and P-selectin binding sites are evolutionary conserved. Functional assays reveal a critical role for post-translational modifications in regulating mammalian PSGL-1 interactions with selectins.</p