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See detailDirect differentiation of time integrators for multibody systems with absolute rotations
Bruls, Olivier ULiege; Eberhard, Peter

in Proceedings of the ECCOMAS Thematic Conference - Multibody Dynamics 2007 (2007)

Gradient-based optimization methods require efficient algorithms to compute the sensitivities of the simulation results with respect to design parameters. Compared to finite difference schemes, the direct ... [more ▼]

Gradient-based optimization methods require efficient algorithms to compute the sensitivities of the simulation results with respect to design parameters. Compared to finite difference schemes, the direct differentiation technique leads to a significant reduction in the computational cost of the sensitivities while keeping a good accuracy. In particular, this paper focuses on the optimization of multibody systems with large rotations. In this framework, two versions of the generalized-alpha time integration scheme are considered: the first one is based on a parameterized treatment of the rotations, whereas the second one is formulated in a geometric setting. We show that the sensitivity analysis is much simpler and computationally more efficient in the second case than in the first case. The performance of both algorithms is compared for a numerical example. [less ▲]

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See detailDirect displacement-based seismic design of an irregular frame - Case study
Massena, B.; Bento, R.; Degée, Hervé ULiege

Report (2008)

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See detailA Direct Dopaminergic Control of Aromatase Activity in the Quail Preoptic Area
Baillien, M.; Balthazart, Jacques ULiege

in Journal of Steroid Biochemistry & Molecular Biology (1997), 63(1-3, Sep-Oct), 99-113

In the quail preoptic area (POA) anatomical and pharmacological data suggest that catecholamines may be implicated in the control of testosterone (T) aromatization into estrogens. The biochemical ... [more ▼]

In the quail preoptic area (POA) anatomical and pharmacological data suggest that catecholamines may be implicated in the control of testosterone (T) aromatization into estrogens. The biochemical mechanism(s) mediating this control of the enzyme activity is (are) however unexplored. The present studies were carried out to investigate whether the catecholamines, dopamine (DA) and norepinephrine (NE) are able to directly affect aromatase activity (AA) measured during in vitro incubations of POA homogenates. AA was quantified in the POA-hypothalamus of adult male Japanese quail by measuring the tritiated water production from [1beta-3H]-androstenedione. Enzyme activity was linear as a function of the incubation time and of the protein content of homogenates. It exhibited a typical Michaelis-Menten kinetics, with an apparent Km of 2.8 nM and a Vmax of 266.6 fmol h(-1) mg wet weight(-1). AA was then measured at a substrate concentration of 25 nM in the presence of catecholamines and some of their receptor agonists or antagonists, at two concentrations, 10(-3) and 10(-6) M. Norepinephrine and prazosin (alpha1-adrenergic antagonist) had no or very limited effects on AA at both concentrations. In contrast, DA and some D1 and/or D2 receptor agonists (apomorphine[D1/D2], SKF-38393 [D1] and RU-24213 [D2]) depressed AA by 40 to 70% at the 10(-3) M concentration. One D2 receptor antagonist also produced a major inhibition of AA (sulpiride) while other antagonists either had no significant effect or only produced moderate decreases in enzyme activity (SCH-23390 [D1], spiperone [D2], pimozide [D2]) as did two DA indirect agonists, amfonelic acid and nomifensine. The inhibitory effect of the agonists was not antagonized by the less active antagonists, SCH-23390 [D1] or spiperone [D2]. Taken together these results suggest that the inhibitory effects do not involve specific binding of DA or its agonists/antagonists to dopaminergic receptors mediating changes in cAMP concentration. This conclusion is also supported by the observation that addition of dibutyryl cAMP did not change brain AA. It appears more likely that DA and dopaminergic drugs inhibit AA by a direct effect on the enzyme, as suggested by the competitive nature of DA and SKF-38393 inhibition of AA (Ki's of 59 and 84 microM, respectively). The functional significance of this effect should still be demonstrated but this mechanism may represent an important physiological pathway through which neurotransmitters could rapidly affect steroid-dependent processes such as the neural synthesis of estrogens. This would provide a mean by which environmental stimuli could affect reproductive behavior and physiology. [less ▲]

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See detailDirect effect of ice sheets on terrestrial bicarbonate, sulphate and base cation fluxes during the last glacial cycle: minimal impact on atmospheric CO2 concentrations
Tranter, Martyn; Huybrechts, Philippe; Munhoven, Guy ULiege et al

in Chemical Geology (2002), 190(1-4), 33-44

Chemical erosion in glacial environments is normally a consequence of chemical weathering reactions dominated by sulphide oxidation linked to carbonate dissolution and the carbonation of carbonates and ... [more ▼]

Chemical erosion in glacial environments is normally a consequence of chemical weathering reactions dominated by sulphide oxidation linked to carbonate dissolution and the carbonation of carbonates and silicates. Solute fluxes from small valley glaciers are usually a linear function of discharge. Representative glacial solute concentrations can be derived from the linear association of solute flux with discharge. These representative glacial concentrations of the major ions are similar to 25% of those in global river water. A 3-D thermomechanically coupled model of the growth and decay of the Northern Hemisphere ice sheets was used to simulate glacial runoff at 100-year time steps during the last glacial cycle (130 ka to the present). The glacially derived fluxes of major cations, anions and Si over the glaciation were estimated from the product of the glacial runoff and the representative glacial concentration. A second estimate was obtained from the product of the glacial runoff and a realistic upper limit for glacial solute concentrations derived from theoretical considerations. The fluxes over the last glacial cycle are usually less than a few percent of current riverine solute fluxes to the oceans. The glacial fluxes were used to provide input to an oceanic carbon cycling model that also calculates changes in atmospheric CO2. The potential change in atmospheric CO2 concentrations over the last glacial cycle that arise from perturbations in glacial solute fluxes are insignificant, being < 1 ppm. [less ▲]

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See detailA direct enzyme-linked immunosorbent assay (Elisa) for antibodies to enterobacterial score glycolipid and lipid A. Results in Healthy Subjects and in Patients Infected by Gram-Negative Bacteria
Nys, Monique ULiege; Damas, Pierre ULiege; Damas, François ULiege et al

in Medical Microbiology & Immunology (1987), 176(5), 257-271

We have developed an ELISA for IgM and IgG antibodies to the core glycolipid (CGL) of the Re mutant Salmonella minnesota R 595, and to lipid A. Anti-CGL antibodies have been detected in sera from 37% of ... [more ▼]

We have developed an ELISA for IgM and IgG antibodies to the core glycolipid (CGL) of the Re mutant Salmonella minnesota R 595, and to lipid A. Anti-CGL antibodies have been detected in sera from 37% of healthy blood donors, whereas anti-lipid A activities were found in 13% of individuals only. The anti-CGL and anti-lipid A activities were examined in patients in a surgical intensive care unit, selected on the basis of a definite risk of infectious complications due to Gram-negative bacteria. Of the patients who developed such infections, the rate of favourable outcome was significantly higher in patients with either stable positive or increasing anti-CGL activities than in patients found to be negative. Our results provide clear evidence that anti-CGL antibodies contribute to host defence against various Gram-negative bacteria. [less ▲]

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See detailDirect estimation of sieve size distributions from 2-D image analysis of sand particles
Pirard, Eric ULiege; Vergara, Nicolas; Chapeau, Vincent

in Proceedings PARTEC 2004 (2004)

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See detailDirect evidence for ferroelectric polar distortion in ultrathin lead titanate perovskite films
Despont, L.; Koitzsch, C.; Clerc, F. et al

in Physical Review. B, Condensed Matter and Materials Physics (2006), 73

X-ray photoelectron diffraction is used to directly probe the intracell polar atomic distortion and tetragonality associated with ferroelectricity in ultrathin epitaxial PbTiO3 films. Our measurements ... [more ▼]

X-ray photoelectron diffraction is used to directly probe the intracell polar atomic distortion and tetragonality associated with ferroelectricity in ultrathin epitaxial PbTiO3 films. Our measurements, combined with ab initio calculations, unambiguously demonstrate noncentrosymmetry in films a few unit cells thick, imply that films as thin as three unit cells still preserve a ferroelectric polar distortion, and also show that there is no thick paraelectric dead layer at the surface. [less ▲]

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See detailDirect evidence for gray seal (Halichoerus grypus) predation and scavenging on harbor porpoises (Phocoena phocoena)
Bouveroux, T.; Kiszka, J.; Heithaus, R. et al

in Marine Mammal Science (2014)

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See detailDirect evidence for grey seal (Halichoerus grypus) predation and scavenging on harbour porpoises (Phocoena phocoena)
Bouveroux, T.; Kiszka, J.; Jauniaux, Thierry ULiege et al

Conference (2014)

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See detailDirect Evidence of Free Radical Production after Ischaemia and Reperfusion and Protective Effect of Desferrioxamine: Esr and Vitamin E Studies
Defraigne, Jean-Olivier ULiege; Detry, Olivier ULiege; Pincemail, Joël ULiege et al

in European Journal of Vascular Surgery (1994), 8(5), 537-43

After surgical renal revascularisation, warm renal ischaemia due to renal artery cross-clamping contributes to postoperative renal dysfunction. After reperfusion, free radicals are thought to be a ... [more ▼]

After surgical renal revascularisation, warm renal ischaemia due to renal artery cross-clamping contributes to postoperative renal dysfunction. After reperfusion, free radicals are thought to be a significant cause of injury. Nevertheless, indisputable proof of free radical production is scarce, partly because of their transient nature. In this study, electron paramagnetic resonance and vitamin E levels were used to demonstrate the free radical production after renal ischaemia and reperfusion. Rabbit kidneys were submitted either to 15 or 60 minutes of ischaemia followed by reperfusion. A spin trap agent (alpha-phenyl-N-tert-butyl nitrone (PBN), 20mg/ml, 1 ml/min) was infused during reperfusion directly into the left renal artery via an aortic catheter before declamping. Blood samples were selectively drawn from the left renal vein for ESR analysis (Varian spectrometer E109) of lipidic residues extracted from blood samples. The vitamin E content of the left renal cortex was determined by HPLC procedure. The right renal cortex was used as a control for the vitamin E values. In the venous effluent, ESR analysis revealed the formation of a spectrum consisting of a triplet of asymmetric doublets. This signal resulted from the spin trapping by PBN of a mixture of both oxygen- and carbon- centred lipidic radicals. The amplitude of the signal which is proportional to the amount of free radicals was significantly higher after 60 minutes ischaemia than after 15 minutes.(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]

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See detailDirect evidence of nonadherence to antiepileptic medication in refractory focal epilepsy
CARPENTIER, Nicolas; Jonas, Jacques; Frismand, Solène et al

in Epilepsia (2013), 54(1), 20-23

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See detailDirect exoplanet detection and characterization using the ANDROMEDA method: Performance on VLT/NaCo data
Cantalloube, F.; Mouillet, D.; Mugnier, L. M. et al

in Astronomy and Astrophysics (2015), 582

Context. The direct detection of exoplanets with high-contrast imaging requires advanced data processing methods to disentangle potential planetary signals from bright quasi-static speckles. Among them ... [more ▼]

Context. The direct detection of exoplanets with high-contrast imaging requires advanced data processing methods to disentangle potential planetary signals from bright quasi-static speckles. Among them, angular differential imaging (ADI) permits potential planetary signals with a known rotation rate to be separated from instrumental speckles that are either statics or slowly variable. The method presented in this paper, called ANDROMEDA for ANgular Differential OptiMal Exoplanet Detection Algorithm is based on a maximum likelihood approach to ADI and is used to estimate the position and the flux of any point source present in the field of view. Aims. In order to optimize and experimentally validate this previously proposed method, we applied ANDROMEDA to real VLT/NaCo data. In addition to its pure detection capability, we investigated the possibility of defining simple and efficient criteria for automatic point source extraction able to support the processing of large surveys. Methods. To assess the performance of the method, we applied ANDROMEDA on VLT/NaCo data of TYC-8979-1683-1 which is surrounded by numerous bright stars and on which we added synthetic planets of known position and flux in the field. In order to accommodate the real data properties, it was necessary to develop additional pre-processing and post-processing steps to the initially proposed algorithm. We then investigated its skill in the challenging case of a well-known target, $\beta$ Pictoris, whose companion is close to the detection limit and we compared our results to those obtained by another method based on principal component analysis (PCA). Results. Application on VLT/NaCo data demonstrates the ability of ANDROMEDA to automatically detect and characterize point sources present in the image field. We end up with a robust method bringing consistent results with a sensitivity similar to the recently published algorithms, with only two parameters to be fine tuned. Moreover, the companion flux estimates are not biased by the algorithm parameters and do not require a posteriori corrections. Conclusions. ANDROMEDA is an attractive alternative to current standard image processing methods that can be readily applied to on-sky data. [less ▲]

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See detailDirect exoplanet imaging with small-angle Vortex coronagraphs
Defrere, Denis ULiege; Absil, Olivier ULiege; Mawet, D. et al

Conference (2015, July 16)

Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They enhance the dynamic range at very small inner working angle ... [more ▼]

Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They enhance the dynamic range at very small inner working angle (down to the diffraction limit of the telescope) and provide a clear 360 degree discovery space for high-contrast direct imaging of exoplanets. In this talk, we will report on the first scientific results obtained with Vortex coronagraphs installed on 10-m class telescopes (i.e., the VLT and the LBT) and on the recent installation of one Vortex at Keck. We will describe the in-lab and on-sky performance of the Vortex, and describe the lessons learned after a few years of operation. Finally, we will discuss the prospects of our vortices for future extremely large telescopes and space missions. [less ▲]

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See detailDirect experimental evidence for atomic tunneling of europium in crystalline Eu8Ga16Ge30
Hermann, Raphaël ULiege; Keppens, Veerle; Bonville, Pierre et al

in Physical Review Letters (2006), 97(1),

Mossbauer-effect and microwave absorption experimental evidence unambiguously demonstrates the presence of slow, similar to 450 MHz, tunneling of magnetic europium between four equivalent sites in ... [more ▼]

Mossbauer-effect and microwave absorption experimental evidence unambiguously demonstrates the presence of slow, similar to 450 MHz, tunneling of magnetic europium between four equivalent sites in Eu8Ga16Ge30, a stoichiometric clathrate. Remarkably, six of the eight europium atoms, or 11% of the constituents in this solid, tunnel between these four sites separated by 0.55 angstrom. The off centering of the atoms or ions in crystalline clathrates appears to be a promising route for producing Rabi oscillators in solid-state materials. [less ▲]

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See detailDirect extraction of hadronic form factors from elastic-scattering data
Martynov, E.; Cudell, Jean-René ULiege; Lengyel, A.

in Nuclear Physics B-Proceedings Supplements (2005, September), 146

Non-forward elastic hadron-scattering data are collected and analysed within the Regge approach. Through an analysis of the data in small bins in t, we have directly extracted the pomeron trajectory and ... [more ▼]

Non-forward elastic hadron-scattering data are collected and analysed within the Regge approach. Through an analysis of the data in small bins in t, we have directly extracted the pomeron trajectory and the hadronic form factors (or reggeon couplings). We found higher values than usually used for the intercept and for the slope of the soft pomeron trajectory. The presence of zeros in t for the effective hadronic form factors is emphasised. [less ▲]

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See detailDirect identification of bacteria from BacT/ALERT anaerobic positive blood cultures by MALDI-TOF MS: MALDI Sepsityper kit versus an in-house saponin method for bacterial extraction.
MEEX, Cécile ULiege; Neuville, Florence; DESCY, Julie ULiege et al

in Journal of Medical Microbiology (2012), 61

In cases of bacteraemia, a rapid species identification of the causal agent directly from positive blood culture broths could assist clinicians in the timely targeting of empirical antimicrobial therapy ... [more ▼]

In cases of bacteraemia, a rapid species identification of the causal agent directly from positive blood culture broths could assist clinicians in the timely targeting of empirical antimicrobial therapy. For this purpose, we evaluated the direct identification of micro-organisms from BacT/ALERT (bioMérieux) anaerobic positive blood cultures without charcoal using the Microflex matrix-assisted laser desorption/ionization (MALDI) time of flight MS (Bruker), after bacterial extraction by using two different methods: the MALDI Sepsityper kit (Bruker) and an in-house saponin lysis method. Bruker's recommended criteria for identification were expanded in this study, with acceptance of the species identification when the first three results with the best matches with the MALDI Biotyper database were identical, whatever the scores were. In total, 107 monobacterial cultures and six polymicrobial cultures from 77 different patients were included in this study. Among monomicrobial cultures, we identified up to the species level 67 and 66 % of bacteria with the MALDI Sepsityper kit and the saponin method, respectively. There was no significant difference between the two extraction methods. The direct species identification was particularly inconclusive for Gram-positive bacteria, as only 58 and 52 % of them were identified to the species level with the MALDI Sepsityper kit and the saponin method, respectively. Results for Gram-negative bacilli were better, with 82.5 and 90 % of correct identification to the species level with the MALDI Sepsityper kit and the saponin method, respectively. No misidentifications were given by the direct procedures when compared with identifications provided by the conventional method. Concerning the six polymicrobial blood cultures, whatever the extraction method used, a correct direct identification was only provided for one of the isolated bacteria on solid medium in all cases. The analysis of the time-to-result demonstrated a reduction in the turnaround time for identification ranging from 1 h 06 min to 24 h 44 min, when performing the blood culture direct identification in comparison with the conventional method, whatever the extraction method. [less ▲]

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See detailDirect imaging constraints on planet populations detected by microlensing
Quanz, S. P.; Lafrenière, D.; Meyer, M. R. et al

in Astronomy and Astrophysics (2012), 541

Context. Results from gravitational microlensing suggested the existence of a large population of free-floating planetary mass objects. The main conclusion from this work was partly based on constraints ... [more ▼]

Context. Results from gravitational microlensing suggested the existence of a large population of free-floating planetary mass objects. The main conclusion from this work was partly based on constraints from a direct imaging survey. This survey determined upper limits for the frequency of stars that harbor giant exoplanets at large orbital separations. <BR /> Aims: We want to verify to what extent upper limits from direct imaging do indeed constrain the microlensing results. <BR /> Methods: We examine the current derivation of the upper limits used in the microlensing study and re-analyze the data from the corresponding imaging survey. We focus on the mass and semi-major axis ranges that are most relevant in context of the microlensing results. We also consider new results from a recent M-dwarf imaging survey as these objects are typically the host stars for planets detected by microlensing. <BR /> Results: We find that the upper limits currently applied in context of the microlensing results are probably underestimated. This means that a larger fraction of stars than assumed may harbor gas giant planets at larger orbital separations. Also, the way the upper limit is currently used to estimate the fraction of free-floating objects is not strictly correct. If the planetary surface density of giant planets around M-dwarfs is described as df[SUB]Planet[/SUB] ∝ a[SUP]β[/SUP]da, we find that β ≲ 0.5-0.6 is consistent with results from different observational studies probing semi-major axes between ~0.03-30 AU. <BR /> Conclusions: Having a higher upper limit on the fraction of stars that may have gas giant planets at orbital separations probed by the microlensing data implies that more of the planets detected in the microlensing study are potentially bound to stars rather than free-floating. The current observational data are consistent with a rising planetary surface density for giant exoplanets around M-dwarfs out to ~30 AU. Future direct imaging surveys will show out to what semi-major axis the above mentioned range of β is valid and what fraction of the planetary mass objects detected by microlensing are indeed bound. [less ▲]

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See detailDirect imaging of Earth-like planets: why we care about exozodis
Absil, Olivier ULiege; Defrere, Denis ULiege; Roberge, A. et al

in Danchi, W. C.; Delplancke, F.; Rajagopal, J. K. (Eds.) Optical and Infrared Interferometry II (2010, July)

The presence of large amounts of exozodiacal dust around nearby main sequence stars is considered as a potential threat for the direct detection of Earth-like exoplanets (exoEarths) with future space ... [more ▼]

The presence of large amounts of exozodiacal dust around nearby main sequence stars is considered as a potential threat for the direct detection of Earth-like exoplanets (exoEarths) with future space-based coronagraphic and interferometric missions. In this paper, we estimate the amount of exozodiacal light that can be tolerated around various stellar types without jeopardizing the detection of exoEarths with a space-based visible coronagraph or a free-flying mid-infrared interferometer. We also address the possible effects of resonant structures in exozodiacal disks. We then review the sensitivity of current ground-based interferometric instruments to exozodiacal disks, based on classical visibility measurements and on the nulling technique. We show that the current instrumental performances are not sufficient to help prepare future exoEarth imaging missions, and discuss how new groundor space-based instruments could improve the current sensitivity to exozodiacal disks down to a suitable level. [less ▲]

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See detailDirect imaging of exoEarths embedded in clumpy debris disks
Defrere, Denis ULiege; Stark, C.; Cahoy, K. et al

in Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave (2012, September 01)

The inner solar system, where the terrestrial planets formed and evolve, is populated by small grains of dust produced by collisions of asteroids and outgassing comets. At visible and infrared wavelengths ... [more ▼]

The inner solar system, where the terrestrial planets formed and evolve, is populated by small grains of dust produced by collisions of asteroids and outgassing comets. At visible and infrared wavelengths, this dust cloud is in fact the most luminous component in the solar system after the Sun itself and the Earth may appear similar to a clump of zodiacal dust to an external observer. Hence, the presence of large amounts of dust in the habitable zone around nearby main-sequence stars is considered as a major hurdle toward the direct imaging of exoEarths with future dedicated space-based telescopes. In that context, we address in this paper the detectability of exoEarths embedded in structured debris disks with future space-based visible coronagraphs and mid-infrared interferometers. Using a collisional grooming algorithm, we produce models of dust clouds that simultaneously and self-consistently handle dust grain dynamics, including resonant interactions with planets, and grain-grain collisions. Considering various viewing geometries, we also derive limiting dust densities that can be tolerated around nearby main-sequence stars in order to ensure the characterization of exoEarths with future direct imaging missions. [less ▲]

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