213 research outputs found
exploding clusters dynamics probed by XUV fluorescence
Clusters excited by intense laser pulses are a unique source of warm dense
matter, that has been the subject of intensive experimental studies. The
majority of those investigations concerns atomic clusters, whereas the
evolution of molecular clusters excited by intense laser pulses is less
explored. In this work we trace the dynamics of clusters
triggered by a few-cycle 1.45-m driving pulse through the detection of XUV
fluorescence induced by a delayed 800-nm ignition pulse. Striking differences
among fluorescence dynamics from different ionic species are observed
Gestion opĂ©rationnelle des transports dâeau dans les canaux et les riviĂšres
AprĂšs une prĂ©sentation gĂ©nĂ©rale historique des canaux d'irrigation, de leur importance stratĂ©gique et des Ă©volutions rĂ©centes, nous dĂ©finissons de maniĂšre plus prĂ©cise les systĂšmes hydrauliques Ă surface libre auxquels nous nous intĂ©ressons dans cet article. Nous prĂ©sentons leurs spĂ©cificitĂ©s qui rendent leur gestion essentielle mais dĂ©licate. Nous prĂ©cisons ensuite ce que nous appelons concrĂštement "gestion", avec diffĂ©rentes nuances, dont la gestion opĂ©rationnelle, et nous utilisons des concepts issus de la gestion industrielle pour mieux l'analyser. Enfin, parmi ces concepts nous dĂ©taillons celui des "machines" permettant de mettre en Âœuvre cette gestion opĂ©rationnelle. / After a historical overview of irrigation canals, their strategic importance and recent trends, we define more precisely the free surface hydraulic systems we analyse in this article. We see that they have features that make their management difficult but essential. Then, we define more precisely what we call "management", with different levels, including "operational management", and we use concepts from production management to better analyze it. Finally, we detail one of these concepts: the "devices" used to implement the operational management
Flatness-based control of open-channel flow in an irrigation canal using SCADA
Open channels are used to distribute water to large irrigated areas. In these systems, ensuring timely water delivery is essential to reduce operational water losses. This article derives a method for open-loop control of open channel flow, based on the Hayami model, a parabolic partial differential equation resulting from a simplification of the Saint-Venant equations. The open-loop control is represented as infinite series using differential flatness. Experimental results show the effectiveness of the approach by applying the open-loop controller to a real irrigation canal located in South of France
Optimal Operation of the Multireservoir System in the Seine River Basin Using Deterministic and Ensemble Forecasts
International audienceThis article investigates the improvement of the operation of a four-reservoir system in the Seine River basin, France, by use of deterministic and ensemble weather forecasts and real-time control. In the current management, each reservoir is operated independently from the others and following prescribed rule-curves, designed to reduce floods and sustain low flows under the historical hydrological conditions. However, this management system is inefficient when inflows are significantly different from their seasonal average and may become even more inadequate to cope with the predicted increase in extreme events induced by climate change. In this work, a centralized real-time control system is developed to improve reservoirs operation by exploiting numerical weather forecasts that are becoming increasingly available. The proposed management system implements a well-established optimization technique, model predictive control (MPC), and its recently modified version that can incorporate uncertainties, tree-based model predictive control (TB-MPC), to account for deterministic and ensemble forecasts respectively. The management system is assessed by simulation over historical events and compared to the no-forecasts strategy based on rule-curves. Simulation results show that the proposed real-time control system largely outperforms the no-forecasts management strategy, and that explicitly considering forecast uncertainty through ensembles can compensate for the loss in performance due to forecast inaccuracy
Caloric restriction induces energy-sparing alterations in skeletal muscle contraction, fiber composition and local thyroid hormone metabolism that persist during catch-up fat upon refeeding.
Weight regain after caloric restriction results in accelerated fat storage in adipose tissue. This catch-up fat phenomenon is postulated to result partly from suppressed skeletal muscle thermogenesis, but the underlying mechanisms are elusive. We investigated whether the reduced rate of skeletal muscle contraction-relaxation cycle that occurs after caloric restriction persists during weight recovery and could contribute to catch-up fat. Using a rat model of semistarvation-refeeding, in which fat recovery is driven by suppressed thermogenesis, we show that contraction and relaxation of leg muscles are slower after both semistarvation and refeeding. These effects are associated with (i) higher expression of muscle deiodinase type 3 (DIO3), which inactivates tri-iodothyronine (T3), and lower expression of T3-activating enzyme, deiodinase type 2 (DIO2), (ii) slower net formation of T3 from its T4 precursor in muscles, and (iii) accumulation of slow fibers at the expense of fast fibers. These semistarvation-induced changes persisted during recovery and correlated with impaired expression of transcription factors involved in slow-twitch muscle development. We conclude that diminished muscle thermogenesis following caloric restriction results from reduced muscle T3 levels, alteration in muscle-specific transcription factors, and fast-to-slow fiber shift causing slower contractility. These energy-sparing effects persist during weight recovery and contribute to catch-up fat
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Farnesoid X Receptor and its ligands inhibit the function of platelets
Objective - While initially seemingly paradoxical due to the lack of nucleus, platelets possess a number of transcription factors that regulate their function through DNA-independent mechanisms. These include the Farnesoid X Receptor (FXR), a member of the superfamily of ligand-activated transcription factors that has been identified as a bile acid receptor. In this study, we show that FXR is present in human platelets and FXR ligands, GW4064 and 6-ECDCA, modulate platelet activation nongenomically.
Approach and Results - FXR ligands inhibited the activation of platelets in response to stimulation of collagen or thrombin receptors, resulting in diminished intracellular calcium mobilization and secretion, fibrinogen binding and aggregation. Exposure to FXR ligands also reduced integrin alphaIIbbeta3 outside-in signaling and thereby reduced the ability of platelets to spread and to stimulate clot retraction. FXR function in platelets was found to be associated with the modulation of cGMP levels in platelets and associated downstream inhibitory signaling. Platelets from FXR-deficient mice were refractory to the actions of FXR agonists on platelet function and cyclic nucleotide signaling, firmly linking the non-genomic actions of these ligands to the FXR receptor.
Conclusion â This study provides support for the ability of FXR ligands to modulate platelet activation. The athero-protective effects of GW4064, with its novel antiplatelet effects, indicate FXR as a potential target for prevention of athero-thrombotic disease
X-ray absorption spectroscopy of iron at multimegabar pressures in laser shock experiments
Green Tea Polyphenol EGCG Sensing Motif on the 67-kDa Laminin Receptor
BACKGROUND: We previously identified the 67-kDa laminin receptor (67LR) as the cell-surface receptor conferring the major green tea polyphenol (-)-epigallocatechin-3-O-gallate (EGCG) responsiveness to cancer cells. However, the underlying mechanism for interaction between EGCG and 67LR remains unclear. In this study, we investigated the possible role of EGCG-67LR interaction responsible for its bioactivities. METHODOLOGY/PRINCIPAL FINDINGS: We synthesized various peptides deduced from the extracellular domain corresponding to the 102-295 region of human 67LR encoding a 295-amino acid. The neutralizing activity of these peptides toward EGCG cell-surface binding and inhibition of cancer cell growth were assayed. Both activities were inhibited by a peptide containing the 10-amino acid residues, IPCNNKGAHS, corresponding to residues 161-170. Furthermore, mass spectrometric analysis revealed the formation of a EGCG-LR161-170 peptide complex. A study of the amino acid deletion/replacement of the peptide LR161-170 indicated that the 10-amino acid length and two basic amino acids, K(166) and H(169), have a critical role in neutralizing EGCG's activities. Moreover, neutralizing activity against the anti-proliferation action of EGCG was observed in a recombinant protein of the extracellular domain of 67LR, and this effect was abrogated by a deletion of residues 161-170. These findings support that the 10 amino-acid sequence, IPCNNKGAHS, might be the functional domain responsible for the anti-cancer activity of EGCG. CONCLUSIONS/SIGNIFICANCE: Overall, our results highlight the nature of the EGCG-67LR interaction and provide novel structural insights into the understanding of 67LR-mediated functions of EGCG, and could aid in the development of potential anti-cancer compounds for chemopreventive or therapeutic uses that can mimic EGCG-67LR interactions
Towards the european strategy for particle physics: The briefing book
This document was prepared as part of the briefing material for the Workshop
of the CERN Council Strategy Group, held in DESY Zeuthen from 2nd to 6th May
2006. It gives an overview of the physics issues and of the technological
challenges that will shape the future of the field, and incorporates material
presented and discussed during the Symposium on the European Strategy for
Particle Physics, held in Orsay from 30th January to 2nd February 2006,
reflecting the various opinions of the European community as recorded in
written submissions to the Strategy Group and in the discussions at the
Symposium
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