Last 7 days     Results 141-160 of 42630.   3 4 5 6 7 8 9 10 11 12 13   Su Marcello Venusti creato di Perino del VagaGeremicca, Antonio in Agosti, Barbara; Leone, Giorgio (Eds.) Intorno a Marcello Venusti (in press)Detailed reference viewed: 17 (4 ULg) Per Francesco Salviati "spirito veramente pellegrino ed eletto"Geremicca, Antonio Book published by Campisano - 1re éd. (in press)Detailed reference viewed: 26 (3 ULg) A Quantitative Doignon-Bell-Scarf theoremAliev, Iskander; Bassett, Robert; De Loera, Jesus et alin Combinatorica (in press)The famous Doignon-Bell-Scarf theorem is a Helly-type result about the existence of integer solutions to systems of linear inequalities. The purpose of this paper is to present the following quantitative ... [more ▼]The famous Doignon-Bell-Scarf theorem is a Helly-type result about the existence of integer solutions to systems of linear inequalities. The purpose of this paper is to present the following quantitative generalization: Given an integer k, we prove that there exists a constant c(n,k), depending only on the dimension n and on the number k, such that if a bounded polyhedron {x in R^n : Ax <= b} contains exactly k integer points, then there exists a subset of the rows, of cardinality no more than c(n,k), defining a polyhedron that contains exactly the same k integer points. In this case c(n,0)=2^n as in the original case of Doignon-Bell-Scarf for infeasible systems of inequalities. We work on both upper and lower bounds for the constant c(n,k) and discuss some consequences, including a Clarkson-style algorithm to find the l-th best solution of an integer program with respect to the ordering induced by the objective function. [less ▲]Detailed reference viewed: 27 (6 ULg) Parametric Polyhedra with at least k Lattice Points: Their Semigroup Structure and the k-Frobenius ProblemAliev, Iskander; De Loera, Jesus; Louveaux, Quentin in Beveridge, Andrew; Griggs, Jerold; Hogben, Leslie (Eds.) et al Recent trends in Combinatorics (in press)The well-studied semigroup Sg(A) = {b : b = Ax; x in Z^n; x >= 0} can be stratified by the sizes of the polyhedral fibers IPA(b) = {x : Ax = b; x >= 0; x in Z^n}. The key theme of this paper is a ... [more ▼]The well-studied semigroup Sg(A) = {b : b = Ax; x in Z^n; x >= 0} can be stratified by the sizes of the polyhedral fibers IPA(b) = {x : Ax = b; x >= 0; x in Z^n}. The key theme of this paper is a structure theory that characterizes precisely the set Sg_k(A) of all vectors b in Sg(A) such that their fiber IPA(b) has at least k-solutions. We demonstrate that this set is finitely generated, a union of translated copies of a semigroup which can be computed explicitly via Hilbert bases computations. Related results can be derived for those right-hand-side vectors b for which IPA(b) has exactly k solutions or fewer than k solutions. We also show that, when n, k are fixed natural numbers, one can compute in polynomial time an encoding of Sg_k(A) as a generating function, using a short sum of rational functions. As a consequence, one can identify all right-hand-side vectors that have at least k solutions. Using this tool we prove that for fixed n; k the k-Frobenius number can be computed in polynomial time, generalizing a well-known result of R. Kannan. [less ▲]Detailed reference viewed: 22 (3 ULg) How to define nativeness in vagile organisms: lessons from the cosmopolitan moss Bryum argenteum on the island of Tenerife (Canary Islands)Pisa, S.C.; Vanderpoorten, Alain ; Patino, J. et alin Plant Biology (in press)Detailed reference viewed: 29 (0 ULg) Why is later age at retirement beneficial for cognition? Results from a French population-based studyGrotz, Catherine ; Meillon, Céline; Amieva, Hélène et alin Journal of Nutrition, Health & Aging (in press)Detailed reference viewed: 31 (9 ULg) Les maisons de Jeanne SusplugasBawin, Julie in Jeanne Susplugas (monographie) (in press)Detailed reference viewed: 32 (9 ULg) De l'état littéraire à une théorie de l'Etat. Une lecture de La Musique et les LettresDurand, Pascal in Millan, Gordon (Ed.) Mallarmé à Tournon et au-delà (in press)Detailed reference viewed: 33 (1 ULg) Lyot-plane phase masks for improved high-contrast imaging with a vortex coronagraphRuane, Garreth J.; Huby, Elsa ; Absil, Olivier et alin Astronomy and Astrophysics (in press)The vortex coronagraph is an optical instrument that precisely removes on-axis starlight allowing for high contrast imaging at small angular separation from the star, thereby providing a crucial ... [more ▼]The vortex coronagraph is an optical instrument that precisely removes on-axis starlight allowing for high contrast imaging at small angular separation from the star, thereby providing a crucial capability for direct detection and characterization of exoplanets and circumstellar disks. Telescopes with aperture obstructions, such as secondary mirrors and spider support structures, require advanced coronagraph designs to provide adequate starlight suppression. We introduce a phase-only Lyot-plane optic to the vortex coronagraph that offers improved contrast performance on telescopes with complicated apertures. Potential solutions for the European Extremely Large Telescope (E-ELT) are described and compared. Adding a Lyot-plane phase mask relocates residual starlight away from a region of the image plane thereby reducing stellar noise and improving sensitivity to off-axis companions. The phase mask is calculated using an iterative phase retrieval algorithm. Numerically, we achieve a contrast on the order of $10^{-6}$ for a companion with angular displacement as small as $4~\lambda/D$ with an E-ELT type aperture. Even in the presence of aberrations, improved performance is expected compared to either a conventional vortex coronagraph or optimized pupil plane phase element alone. [less ▲]Detailed reference viewed: 16 (0 ULg) Post-coronagraphic tip-tilt sensing for vortex phase masks: the QACITS techniqueHuby, Elsa ; Baudoz, Pierre; Mawet, Dimitri et alin Astronomy and Astrophysics (in press)Small inner working angle coronagraphs, like the vortex phase mask, are essential to exploit the full potential of ground-based telescopes in the context of exoplanet detection and characterization ... [more ▼]Small inner working angle coronagraphs, like the vortex phase mask, are essential to exploit the full potential of ground-based telescopes in the context of exoplanet detection and characterization. However, the drawback of this attractive feature is a high sensitivity to pointing errors, which degrades the performance of the coronagraph. We propose a tip-tilt retrieval technique based on the analysis of the final coronagraphic image, hereafter called Quadrant Analysis of Coronagraphic Images for Tip-tilt Sensing (QACITS). Under the assumption of small phase aberrations, we show that the behaviour of the vortex phase mask can be simply described from the entrance pupil to the Lyot stop plane by Zernike polynomials. This convenient formalism is used to establish the theoretical basis of the QACITS technique. Simulations have been performed to demonstrate the validity and limits of the technique, including the case of a centrally obstructed pupil. The QACITS technique principle is further validated by experimental results in the case of an unobstructed circular aperture. The typical configuration of the Keck telescope (24% central obstruction) has been simulated with additional high order aberrations. In these conditions, our simulations show that the QACITS technique is still adapted to centrally obstructed pupils and performs tip-tilt retrieval with a precision of $5 \times 10^{-2}$ {\lambda}/D when wavefront errors amount to {\lambda}/14 rms and $10^{-2}$ {\lambda}/D for {\lambda}/70 rms errors (with {\lambda} the wavelength and D the pupil diameter). The implementation of the QACITS technique is based on the analysis of the scientific image and does not require any modification of the original setup. Current facilities equipped with a vortex phase mask can thus directly benefit from this technique to improve the contrast performance close to the axis. [less ▲]Detailed reference viewed: 12 (0 ULg) Ageism and caring attitudes among nurses in oncologySchroyen, Sarah ; Missotten, Pierre ; Jerusalem, Guy et alin International Psychogeriatrics (in press)Detailed reference viewed: 65 (9 ULg) FLOR-ID: an interactive database of flowering-time gene networks in Arabidopsis thalianaBouché, Frédéric ; Lobet, Guillaume ; Tocquin, Pierre et alin Nucleic Acids Research (in press)Flowering is a hot topic in Plant Biology and important progress has been made in Arabidopsis thaliana toward unravelling the genetic networks involved. The increasing complexity and the explosion of ... [more ▼]Flowering is a hot topic in Plant Biology and important progress has been made in Arabidopsis thaliana toward unravelling the genetic networks involved. The increasing complexity and the explosion of literature however require development of new tools for information management and update. We therefore created an evolutive and interactive database of flowering time genes, named FLOR-ID (Flowering-Interactive Database), that is available freely at http://www.flor-id.org. The hand-curated database contains information on 306 genes and links to 1595 publications gathering the work of more than 4500 authors. Gene function and interactions within the flowering pathways were inferred from the analysis of related publications, included in the database and translated into interactive manually drawn snapshots. [less ▲]Detailed reference viewed: 128 (33 ULg) Du Blioul (Laurent): 1454 ou 1455-1542Regibeau, Julien in Nouvelle biographie nationale. 15 (in press)Detailed reference viewed: 16 (4 ULg) Il grande «incubo che mi son scelto». Le grand «cauchemar de mon choix». The big «nightmare of my choice». Prove di avvicinamento a Profondo rosso / Les Frissons de l'Angoisse / Deep Red (1975-2015)Curreri, Luciano ; Delville, Michel Book published by Il foglio (in press)Detailed reference viewed: 25 (1 ULg) Potential of copper-tolerant grasses to implement phytostabilisation strategies on polluted soils in South D. R. Congo: Poaceae candidates for phytostabilisationBoisson, Sylvain ; Le Stradic, Soizig ; Collignon, Julien et alin Environmental Science and Pollution Research (in press)Phytostabilisation (i.e. using plants to immobilise contaminants) represents a well-known technology to hamper heavy metal spread across landscapes. In Katanga (D. R. Congo), Microchloa altera, a tolerant ... [more ▼]Phytostabilisation (i.e. using plants to immobilise contaminants) represents a well-known technology to hamper heavy metal spread across landscapes. In Katanga (D. R. Congo), Microchloa altera, a tolerant grass from the copper hills, was recently identified as a candidate species to stabilise copper in the soil. More than 50 grasses compose this flora, which may be studied to implement phytostabilisation strategies. However, little is known about their phenology, tolerance, reproductive strategy or demography. The present study aims to characterize the other Poaceae that may be used in phytostabilisation purposes based on the following criteria: their ecological distribution, seed production at two times, abundance, soil coverage and the germination percentage of their seeds. We selected seven perennial Poaceae that occur on the copper hills. Their ecological distributions (i.e. species response curves) have been modelled along copper or cobalt gradients with generalized additive models using logic link based on 172 presence/absence samples on three sites. For other variables, a total of 69 quadrats (1 m2) were randomly placed across three sites and habitats. For each species, we compared the number of inflorescence-bearing stems (IBS) by plot, the percentage of cover, the number of seeds by IBS and the estimated number of seeds by plot between sites and habitat. Three species (Andropogon schirensis, Eragrostis racemosa and Loudetia simplex) were very interesting for phytostabilisation programs. They produced a large quantity of seeds and had the highest percentage of cover. However, A. schirensis and L. simplex presented significant variations in the number of seeds and the percentage of cover according to site. [less ▲]Detailed reference viewed: 27 (10 ULg) Residue and microwear analyses of the stone tools from SchöningenRots, Veerle ; Hardy, Bruce; Serangeli, Jordi et alin Journal of Human Evolution (in press)Detailed reference viewed: 70 (23 ULg) The Bounds of Object. The Brentano-Meinong Dispute, A Priori Knowledge, and the Power of PerceptionBoccaccini, Federico in Leclercq, Bruno; Richard, Sébastien; Seron, Denis (Eds.) Objects and Pseudo-Objects. Ontological deserts and jungles from Meinong to Carnap (in press)Detailed reference viewed: 18 (0 ULg) Gateways and Walls, or the Power and Pitfalls of Postcolonial MetaphorsTunca, Daria ; Wilson, Janetin Wilson, Janet; Tunca, Daria (Eds.) Under Construction: Postcolonial Gateways and Walls (in press)Detailed reference viewed: 22 (0 ULg) Data-driven selection of the minimum-gradient support parameter in time-lapse focused electrical imagingNguyen, Frédéric ; Robert, Tanguy; Kemna, Andreas et alin Geophysics (in press)We consider the problem of the choice of the minimum gradient support parameter in focused inversion for time-lapse electrical resistivity tomography. Most existing approaches rely either on an arbitrary ... [more ▼]We consider the problem of the choice of the minimum gradient support parameter in focused inversion for time-lapse electrical resistivity tomography. Most existing approaches rely either on an arbitrary choice of this parameter or is based on prior information such as the expected contrast in the time-lapse image. We propose to select the minimum gradient support parameter using a line search based on the value of the time-lapse data root mean square misfit at the first iteration of the non-linear inversion procedure. The latter is based on a Gauss-Newton scheme minimizing a regularized objective function where the regularization functional is defined by the minimum gradient support functional. The regularization parameter is optimized to achieve a certain target level, following Occam principles. We validate our approach on a synthetic benchmark using a complex and heterogeneous model and demonstrate its effectiveness on electrical tomography time-lapse data collected during a salt tracer experiment in fractured limestone. Our results show that the approach is successful in retrieving the focused anomaly and does not rely on prior information. [less ▲]Detailed reference viewed: 43 (4 ULg) All for a container! Return migration, transport technologies, and love affairsJedlowski, Alessandro in Transfers: Interdisciplinary Journal of Mobility Studies (in press)This paper analyzes the articulation between mobility and technology within life trajectories marked by migration, exile and the search for economic achievement. It does so by focusing on a Nigerian ... [more ▼]This paper analyzes the articulation between mobility and technology within life trajectories marked by migration, exile and the search for economic achievement. It does so by focusing on a Nigerian couple’s (attempted) itinerary of return migration from Italy to Nigeria, and on the tensions that surround the role played by a specific transport technology, the shipping container, within this process. It highlights how, throughout the itinerary that brings the container from Italy to Nigeria, its social meaning and that of the cargo stored in it become the center of a series of tense interactions, in which diverging imaginaries about transnational mobility, migration and life abroad come to the fore, and provoke radical transformations in the life of the people involved in the itinerary of the container itself. [less ▲]Detailed reference viewed: 37 (9 ULg)