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On the 3D Reconstruction of Coronal Mass Ejections using Coronagraph Data
No full textCoronal Mass ejections (CMEs) are enormous eruptions of magnetized plasma expelled from the Sun into the interplanetary space, over the course of hours to days. They can create major disturbances in the interplanetary medium and trigger severe magnetic storms when they col- lide with the Earth’s magnetosphere. It is important to know their real speed, propagation direction and 3D configura- tion in order to accurately predict their arrival time at the Earth. Using data from the SECCHI coronagraphs onboard the STEREO mission, which was launched in October 2006, we can infer the propagation direction and the 3D struc- ture of such events. In this review, we first describe differ- ent techniques that were used to model the 3D configuration of CMEs in the coronagraph field of view (up to 15 R⊙). Then, we apply these techniques to different CMEs observed by various coronagraphs. A comparison of results obtained from the application of different reconstruction algorithms is presented and discussed.LTS2LTS
Exopolysaccharides produced by bacteria isolated from the pelagic Southern Ocean - Role in Fe binding, chemical reactivity, and bioavailability
No full textAs a result of ubiquitous excretion by micro-organisms, extracellular polymeric substances are reported in high concentrations in marine systems. The majority of this material is exopolysaccharide (EPS). Despite previous studies showing that EPS can affect carbon as well as trace metal cycling, little is known about the effect on Fe - a critical nutrient limiting primary productivity in up to 40% of the ocean. Here, we have characterised an EPS purified from bacteria isolated from the pelagic Southern Ocean (Pseudoalteromonas sp.) and investigated its role in Fe chemical speciation, solubility, as well as bioavailability for two keystone Southern Ocean phytoplankton strains. This EPS has an average molecular weight of 4.6 MDa, exhibiting mainly -OH. COO- and -NH2 functional groups. An asymmetrical flow field-flow fractionation coupled online with UV-spectrophotometer, differential refractive index, and multiangle laser light scattering (aFIFFF-UV-DRI-MALS) demonstrates that this EPS is polydisperse with three, not well resolved, size populations having molar masses in the range from 0.57 to 15.8 MDa. Fe was exclusively associated with the medium size fraction of this EPS and was the most abundant trace metal with 2.2 nM Fe per nM EPS. Only a third of this Fe was chemically labile, and the strength of Fe-EPS complexes increased with equilibration time. 1 nM EPS is efficient to retain Fe in solution, mainly in the colloidal phase (0.02-0.2 mu m). Fe bound to the EPS was highly bioavailable (25% as much as for inorganic Fe). Due to combined effect of EPS on Fe solubility and bioavailability, it can increase the residence time of bioavailable Fe in the euphotic zone, therefore possibly sustaining and controlling primary productivity in sensitive oceanic regions, such as the Southern Ocean. (C) 2010 Elsevier B.V. All rights reserved.GR-SL
Portfolio and welfare consequences of debt market dominance
No full textThe ability to issue debt that pays in units of the domestic good leads a country to accumulate a large and negative net foreign asset position while maintaining a positive position in equity. This debt market advantage also helps to explain the weak relationship between the real exchange rate and relative consumption. Our stylized model matches the key facts about the U.S. international portfolio, the U.S. real exchange rate, and explains nearly 50% of the observed variation in the valuation effects. We find that taxing bond market transactions increases the volatility of the exchange rate, capital flows and allocations. In contrast, taxing equity positions stabilizes the exchange rate and capital flows while having little impact on the allocation. Lastly, the paper describes a global solution method for portfolio problems under incomplete markets. (C) 2015 Elsevier B.V. All rights reserved.SFI-L
Détection, suivi et identification de la communauté microbienne du biofilm lors du démarrage de deux réacteurs intensifs de méthanisation traitant des effluents viticoles
No full textSCGCDIPLOMES; GR - 53 504; EPFL - SB - ISIC ; . Consultable sur demande à la Bibliothèque de l'EPFL / Offered in consultation at the EPFL library
Content Preference Estimation In Online Social Networks: Message Passing Versus Sparse Reconstruction On Graphs
No full textWe design two different strategies for computing the unknown content preferences in an online social network based on a small set of nodes in the corresponding social graph for which this information is available ahead of time. The techniques take advantage of the graph's structure and the additional affinity information between the social contacts, expressed through the graph's edge weights, to optimize the computation of the missing preference data. The first strategy is distributed and comprises a local computation step and a message passing step that are iteratively applied at each node in the graph, until convergence. We carry out a graph Laplacian based analysis of the performance of the algorithm and verify the analytical findings via numerical experiments involving sample social networks. The second strategy is centralized and involves a sparse transform of the content preference data represented as a function over the nodes of the social graph. We solve the related optimization problem of reconstructing the unknown preferences via an iterative algorithm based on variable splitting and alternating direction of multipliers. The algorithm takes into account the specifics of the data to be reconstructed by incorporating multiple regularization terms into the optimization. We investigate the underpinnings of the sparse reconstruction technique via numerical experiments that reveal its characteristics and how they affect its performance.LTS
Advances in polymer-based nanocomposite membranes for water remediation: Preparation methods, critical issues and mechanisms
No full textMembrane technology is a growing tool for contaminants removal from polluted water. Although various types of polymeric membranes have been developed for water remediation, the common drawbacks like fouling, hydrophobicity and low mechanical strength are yet to be suitably addressed. Most of the research is directed towards the development of polymer nanocomposites viz., incorporating different nanomaterials into polymer matrices enhancing bare polymer matrices' properties. In this paper, we discuss different strategies for preparing polymer nanocomposite membranes, their performance, and critical issues to be addressed. In addition, we discussed the scalability and the economic feasibility of membrane-based systems for wastewater treatment.ISI
Velocity tracking based on adaptive Doppler filters
No full textIn order to obtain target velocity in radar systems we use Doppler filters. It is usual in such applications to use window functions with prespecified shape and length. For a good target velocity estimation, it is necessary to apply adaptive length window functions. The optimum length is primarily influenced by the target dynamics, expressed in its acceleration, and the signal to noise ratio of the obtained echo. In this paper, we have proposed a very simple and accurate procedure for an estimation of the target acceleration. We assumed signal to noise ratio to be constant. The efficiency of the procedure has been demonstrated through computer simulations.LCS
Integration of ISS into the Viola Meta-Scheduling Environment, Integrated Research in GRID Computing
No full textThe authors present the integration of the Intelligent (Grid) Scheduling System into the VIOLA meta-scheduling environment which itself is based on the UNI-CORE Grid software. The goal of the new, integrated environment is to enable the submission of jobs to the Grid system best-suited for the application work-flow. For this purpose a cost function is used that exploits information about the type of application, the characteristics of the system architectures, as well as the availabilities of the resources. This document presents an active collaboration between Ecole Polytechnique Fédérate de Lausanne (EPFL), Ecole d’Ingénieurs et d’Architectes (EIF) de Fribourg, Forschungszentrum Jülich, Fraunhofer Institute SCAI, and Swiss National Supercomputing Centre (CSCS).LI