Last 7 days
Bookmark and Share    
Full Text
Peer Reviewed
See detailRaman Chemical Imaging in Kidney Stone Analysis
Castiglione, Vincent ULiege; Sacre, Pierre-Yves ULiege; CAVALIER, Etienne ULiege et al

Poster (2017, November 02)

Background: The structure of kidney stones might provide clinical useful information in addition to the stone composition. The Raman chemical imaging (RCI) is a new technology used for the production of ... [more ▼]

Background: The structure of kidney stones might provide clinical useful information in addition to the stone composition. The Raman chemical imaging (RCI) is a new technology used for the production of two-dimensions maps of the constituents' distribution in samples. We aimed at determining the use of RCI in urinary stone analysis. Methods: Twelve calculi were analyzed by RCI using a confocal Raman microspectrophotometer. They were selected according to their heterogeneous composition and morphology. Prior to the analysis, samples were sliced and milled in order to detect the nucleus of the stones and having a smooth surface. RCI was performed on the whole section of stones. Once acquired, the data were baseline corrected and analyzed by MCR-ALS. Results were then compared to the spectra obtained by Fourier Transform Infrared spectroscopy, the gold standard method for the determination of urolithiasis composition. Results: RCI succeeded in identifying all the chemical components contained in each sample, including monohydrate and dihydrate calcium oxalate, anhydrous and dihydrate uric acid, apatite, struvite, brushite, whitlockite and ammonium urate. However, proteins couldn't be detected because of the huge autofluorescence background and the small concentration of these poor Raman scatterers. Carbapatite and calcium oxalate were correctly detected even when they represented less than 5 percent of the whole stones, allowing the detection of very small structures like Randall's plaques. Moreover, RCI provided the distribution of components within the stones. The nuclei were accurately identified, as well as thin layers of other components. Conversion of dihydrate to monohydrate calcium oxalate was correctly observed in the center of one sample. Conclusion: RCI showed a good accuracy in comparison with infrared spectroscopy in identifying components of kidney stones. In addition, RCI is nondestructive enabling the storage of samples. This analysis was also useful in determining the organization of components within stones, which help locating constituents in low quantity, such as nuclei. However, this analysis is time-consuming, which makes it more suitable for research studies rather than routine analysis. [less ▲]

Detailed reference viewed: 43 (1 ULiège)
Full Text
Peer Reviewed
See detailEffects of Transcranial Direct Current Stimulation, Transcranial Pulsed Current Stimulation, and Their Combination on Brain Oscillations in Patients with Chronic Visceral Pain: A Pilot Crossover Randomized Controlled Study.
Thibaut, Aurore ULiege; Russo, Cristina; Hurtado-Puerto, Aura-Maria et al

in Frontiers in Neurology (2017)

Objective: Chronic visceral pain (CVP) syndromes are persistently painful disorders with a remarkable lack of effective treatment options. This study aimed at evaluating the effects of different ... [more ▼]

Objective: Chronic visceral pain (CVP) syndromes are persistently painful disorders with a remarkable lack of effective treatment options. This study aimed at evaluating the effects of different neuromodulation techniques in patients with CVP on cortical activity, through electreocephalography (EEG) and on pain perception, through clinical tests. Design:A pilot crossover randomized controlled study. Settings: Out-patient. Subjects: Adults with CVP (>3 months). Methods: Participants received four interventions in a randomized order: (1) transcranial pulsed current stimulation (tPCS) and active transcranial direct current stimulation (tDCS) combined, (2) tPCS alone, (3) tDCS alone, and (4) sham condition. Resting state quantitative electroencephalography (qEEG) and pain assessments were performed before and after each intervention. Results were compared with a cohort of 47 healthy controls. Results: We enrolled six patients with CVP for a total of 21 visits completed. Compared with healthy participants, patients with CVP showed altered cortical activity characterized by increased power in theta, alpha and beta bands, and a significant reduction in the alpha/beta ratio. Regarding tES, the combination of tDCS with tPCS had no effect on power in any of the bandwidths, nor brain regions. Comparing tPCS with tDCS alone, we found that tPCS induced higher increase in power within the theta and alpha bandwidths. Conclusion: This study confirms that patients with CVP present abnormal EEG-indexed cortical activity compared with healthy controls. Moreover, we showed that combining two types of neurostimulation techniques had no effect, whereas the two interventions, when applied individually, have different neural signatures. [less ▲]

Detailed reference viewed: 22 (0 ULiège)
Full Text
Peer Reviewed
See detailAn X-ray view of HD 166734, a massive supergiant system
Nazé, Yaël ULiege; Gosset, Eric ULiege; Mahy, Laurent ULiege et al

in Astronomy and Astrophysics (2017), 607(A97), 1-10

The X-ray emission of the O+O binary HD 166734 was monitored using Swift and XMM-Newton observatories, leading to the discovery of phase-locked variations. The presence of an f line in the He-like ... [more ▼]

The X-ray emission of the O+O binary HD 166734 was monitored using Swift and XMM-Newton observatories, leading to the discovery of phase-locked variations. The presence of an f line in the He-like triplets further supports a wind-wind collision as the main source of the X-rays in HD 166734. While temperature and absorption do not vary significantly along the orbit, the X-ray emission strength varies by one order of magnitude, with a long minimum state (Δ(φ) 0.1) occurring after a steep decrease. The flux at minimum is compatible with the intrinsic emission of the O-stars in the system, suggesting a possible disappearance of colliding wind emission. While this minimum cannot be explained by eclipse or occultation effects, a shock collapse may occur at periastron in view of the wind properties. Afterwards, the recovery is long, with an X-ray flux proportional to the separation d (in hard band) or to d[SUP]2[/SUP] (in soft band). This is incompatible with an adiabatic nature for the collision (which would instead lead to F[SUB]X[/SUB] ∝ 1 /d), but could be reconciled with a radiative character of the collision, though predicted temperatures are lower and more variable than in observations. An increase in flux around φ 0.65 and the global asymmetry of the light curve remain unexplained, however. Based on observations collected with Swift and the ESA science mission XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). [less ▲]

Detailed reference viewed: 16 (3 ULiège)
Full Text
Peer Reviewed
See detailHigh-precision multi-wavelength eclipse photometry of the ultra-hot gas giant exoplanet WASP-103 b
Delrez, L.; Madhusudhan, N.; Lendl, M. et al

in Monthly Notices of the Royal Astronomical Society (2017), 474(2), 2334-2351

We present sixteen occultation and three transit light curves for the ultra-short period hot Jupiter WASP-103 b, in addition to five new radial velocity measurements. We combine these observations with ... [more ▼]

We present sixteen occultation and three transit light curves for the ultra-short period hot Jupiter WASP-103 b, in addition to five new radial velocity measurements. We combine these observations with archival data and perform a global analysis of the resulting extensive dataset, accounting for the contamination from a nearby star. We detect the thermal emission of the planet in both the $z'$ and $K_{\mathrm{S}}$-bands, the measured occultation depths being 699$\pm$110 ppm (6.4-$\sigma$) and $3567_{-350}^{+400}$ ppm (10.2-$\sigma$), respectively. We use these two measurements together with recently published HST/WFC3 data to derive joint constraints on the properties of WASP-103 b's dayside atmosphere. On one hand, we find that the $z'$-band and WFC3 data are best fit by an isothermal atmosphere at 2900 K or an atmosphere with a low H$_2$O abundance. On the other hand, we find an unexpected excess in the $K_{\mathrm{S}}$-band measured flux compared to these models, which requires confirmation with additional observations before any interpretation can be given. From our global data analysis, we also derive a broad-band optical transmission spectrum that shows a minimum around 700 nm and increasing values towards both shorter and longer wavelengths. This is in agreement with a previous study based on a large fraction of the archival transit light curves used in our analysis. The unusual profile of this transmission spectrum is poorly matched by theoretical spectra and is not confirmed by more recent observations at higher spectral resolution. Additional data, both in emission and transmission, are required to better constrain the atmospheric properties of WASP-103 b. [less ▲]

Detailed reference viewed: 15 (1 ULiège)
Full Text
Peer Reviewed
See detailSeismic inversion of the solar entropy. A case for improving the standard solar model
Buldgen, Gaël ULiege; Salmon, Sébastien ULiege; Noels-Grötsch, Arlette ULiege et al

in Astronomy and Astrophysics (2017), 607

Context. The Sun is the most constrained and well-studied of all stars. As a consequence, the physical ingredients entering solar models are used as a reference to study all other stars observed in the ... [more ▼]

Context. The Sun is the most constrained and well-studied of all stars. As a consequence, the physical ingredients entering solar models are used as a reference to study all other stars observed in the Universe. However, our understanding of the solar structure is still imperfect, as illustrated by the current debate on the heavy element abundances in the Sun. <BR /> Aims: We provide additional information on the solar structure by carrying out structural inversions of a new physical quantity, a proxy of the entropy of the solar plasma whose properties are very sensitive to the temperature gradient below the convective zone. <BR /> Methods: We use new structural kernels to carry out direct inversions of an entropy proxy of the solar plasma and compare the solar structure to various standard solar models built using various opacity tables and chemical abundances. We also link our results to classical tests commonly found in the literature. <BR /> Results: Our analysis allows us to probe more efficiently the uncertain regions of the solar models, just below the convective zone, paving the way for new in-depth analyses of the Sun taking into account additional physical uncertainties of solar models beyond the specific question of chemical abundances. [less ▲]

Detailed reference viewed: 14 (2 ULiège)
Full Text
Peer Reviewed
See detailIncreasing plant functional diversity is not the key for supporting pollinators in wildflower strips
Uyttenbroeck, Roel ULiege; Piqueray, Julien; Hatt, Séverin ULiege et al

in Agriculture, Ecosystems & Environment (2017), 249

Intensification of agriculture has been one of the major drivers for biodiversity loss in recent decades. Pollinators, which serve an important role in pollinating crops as well as wild plants, have shown ... [more ▼]

Intensification of agriculture has been one of the major drivers for biodiversity loss in recent decades. Pollinators, which serve an important role in pollinating crops as well as wild plants, have shown a decline in species richness. Flower strips can be used to support pollinators in agro-ecosystems, however the question remains as to how their design can be optimized in order to best benefit pollinators. Increasing plant species diversity has been shown to be beneficial for pollinators, and it is often suggested that functional traits are driving this relationship. Therefore, increasing plant functional diversity could be a tool to support pollinator abundance and diversity. As experimental evidence on this relationship is scarce, we developed a field study with experimental sown flower strips with four functional diversity levels, based on multiple flower traits and with equal plant species richness. We monitored vegetation development, as well as the flower-visiting pollinator community and their interaction networks with flowers. We were able to create a functional diversity gradient while controlling for plant species richness and evenness. However, in contrast to our expectations, pollinator species richness and evenness were not influenced by functional diversity, and increasing functional diversity even resulted in lower flower visitation rates. Network stability metrics showed no effect or negative relationships with functional diversity. We conclude that increasing functional diversity was not the key for supporting pollinators in wildflower strips. Our results also suggest that, for a constant amount of flower resources, increasing plant functional diversity and thus decreasing redundancy of potential pollinator feeding niches, decreases the amount of flower resources present per feeding niche. As pollinator species tended to have less overlap in their feeding niches in flower strips with increased functional diversity, this may lead to a reduction of flower resources available for pollinator species with a more specialized feeding niche. [less ▲]

Detailed reference viewed: 49 (4 ULiège)
Full Text
Peer Reviewed
See detailA modern study of HD 166734: a massive supergiant system
Mahy, Laurent ULiege; Damerdji, Yassine ULiege; Gosset, Eric ULiege et al

in Astronomy and Astrophysics (2017), 607

Aims: HD 166734 is an eccentric eclipsing binary system composed of two supergiant O-type stars, orbiting with a 34.5-day period. In this rare configuration for such stars, the two objects mainly evolve ... [more ▼]

Aims: HD 166734 is an eccentric eclipsing binary system composed of two supergiant O-type stars, orbiting with a 34.5-day period. In this rare configuration for such stars, the two objects mainly evolve independently, following single-star evolution so far. This system provides a chance to study the individual parameters of two supergiant massive stars and to derive their real masses. Methods: An intensive monitoring was dedicated to HD 166734. We analyzed mid- and high-resolution optical spectra to constrain the orbital parameters of this system. We also studied its light curve for the first time, obtained in the VRI filters. Finally, we disentangled the spectra of the two stars and modeled them with the CMFGEN atmosphere code in order to determine the individual physical parameters. Results: HD 166734 is a O7.5If+O9I(f) binary. We confirm its orbital period but we revise the other orbital parameters. In comparison to what we found in the literature, the system is more eccentric and, now, the hottest and the most luminous component is also the most massive one. The light curve exhibits only one eclipse and its analysis indicates an inclination of 63.0° ± 2.7°. The photometric analysis provides us with a good estimation of the luminosities of the stars, and therefore their exact positions in the Hertzsprung-Russell diagram. The evolutionary and the spectroscopic masses show good agreement with the dynamical masses of 39.5 M[SUB]⊙[/SUB] for the primary and 33.5 M[SUB]⊙[/SUB] for the secondary, within the uncertainties. The two components are both enriched in helium and in nitrogen and depleted in carbon. In addition, the primary also shows a depletion in oxygen. Their surface abundances are however not different from those derived from single supergiant stars, yielding, for both components, an evolution similar to that of single stars. Based on observations collected at the European Southern Observatory (La Silla, Chile) with FEROS and TAROT and on data collected at the San Pedro Mártir observatory (Mexico).The reduced spectra and the light curves are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A96">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A96</A> [less ▲]

Detailed reference viewed: 17 (0 ULiège)
Full Text
Peer Reviewed
See detailImproving fungal disease forecasts in winter wheat: A critical role of intra-day variations of meteorological conditions in the development of Septoria leaf blotch
El Jarroudi, Moussa ULiege; kOUADIO, Louis; EL JARROUDI, Mustapha et al

in Field Crops Research (2017), 213

Meteorological conditions are important factors in the development of fungal diseases in winter wheat and are the main inputs of the decision support systems used to forecast disease and thus determine ... [more ▼]

Meteorological conditions are important factors in the development of fungal diseases in winter wheat and are the main inputs of the decision support systems used to forecast disease and thus determine timing for efficacious fungicide application. This study uses the Fourier transform method (FTM) to characterize temporal patterns of meteorological conditions between two neighbouring experimental sites used in a regional fungal disease monitoring and forecasting experiment in Luxembourg. Three meteorological variables (air temperature, relative humidity, and precipitation) were included, all conducive to infection of wheat by Zymoseptoria tritici cause of Septoria leaf blotch (STB) in winter wheat, from 2006 to 2009. The intraday, diurnal, dekadal and intra-seasonal variations of the meteorological variables were assessed using FTM, and the impact of existing contrasts between sites on the development of STB was analyzed. Although STB severities varied between sites and years (P ≤ 0.0003), the results indicated that the two sites presented the same patterns of meteorological conditions when compared at larger temporal scales (diurnal to intra-seasonal scales, with time periods >11 h). However, the intraday variations of all the variables were well discriminated between the sites and were highly correlated to STB severities. Our findings highlight and confirm the importance of intraday meteorological variation in the development of STB in winter wheat fields. Furthermore, the FTM approach has potential for identifying microclimatic conditions prevailing at given sites and could help in improving the prediction of disease forecast models used in regional warning systems. [less ▲]

Detailed reference viewed: 26 (3 ULiège)
Full Text
Peer Reviewed
See detailH0LiCOW VII: cosmic evolution of the correlation between black hole mass and host galaxy luminosity
Ding, Xuheng; Treu, Tommaso; Suyu, Sherry H. et al

in Monthly Notices of the Royal Astronomical Society (2017), 472

Strongly lensed active galactic nuclei (AGN) provide a unique opportunity to make progress in the study of the evolution of the correlation between the mass of supermassive black holes (M_BH) and their ... [more ▼]

Strongly lensed active galactic nuclei (AGN) provide a unique opportunity to make progress in the study of the evolution of the correlation between the mass of supermassive black holes (M_BH) and their host galaxy luminosity (L[SUB]host[/SUB]). We demonstrate the power of lensing by analysing two systems for which state-of-the-art lens modelling techniques have been applied to deep Hubble Space Telescope imaging data. We use (i) the reconstructed images to infer the total and bulge luminosity of the host and (ii) published broad-line spectroscopy to estimate M_BH using the so-called virial method. We then enlarge our sample with new calibration of previously published measurements to study the evolution of the correlation out to z ˜ 4.5. Consistent with previous work, we find that without taking into account passive luminosity evolution, the data points lie on the local relation. Once the passive luminosity evolution is taken into account, we find that black holes in the more distant Universe reside in less luminous galaxies than today. Fitting this offset as M_BH/L[SUB]host[/SUB] ∝ (1 + z)[SUP]γ[/SUP], and taking into account selection effects, we obtain γ = 0.6 ± 0.1 and 0.8 ± 0.1 for the case of M_BH-L[SUB]bulge[/SUB] and M_BH-L[SUB]total[/SUB], respectively. To test for systematic uncertainties and selection effects we also consider a reduced sample that is homogeneous in data quality. We find consistent results but with considerably larger uncertainty due to the more limited sample size and redshift coverage (γ = 0.7 ± 0.4 and 0.2 ± 0.5 for M_BH-L[SUB]bulge[/SUB] and M_BH-L[SUB]total[/SUB], respectively), highlighting the need to gather more high-quality data for high-redshift lensed quasar hosts. Our result is consistent with a scenario where the growth of the black hole predates that of the host galaxy. [less ▲]

Detailed reference viewed: 19 (1 ULiège)
Full Text
Peer Reviewed
See detailMulti-temporal monitoring of a regional riparian buffer network (>12,000 km) with LiDAR and photogrammetric point clouds
Michez, Adrien ULiege; Piégay, Hervé; Lejeune, Philippe ULiege et al

in Journal of Environmental Management (2017), 202(2), 424-436

Riparian buffers are of major concern for land and water resource managers despite their relatively low spatial coverage. In Europe, this concern has been acknowledged by different environmental ... [more ▼]

Riparian buffers are of major concern for land and water resource managers despite their relatively low spatial coverage. In Europe, this concern has been acknowledged by different environmental directives which recommend multi-scale monitoring (from local to regional scales). Remote sensing methods could be a cost-effective alternative to field-based monitoring, to build replicable “wall-to-wall” monitoring strategies of large river networks and associated riparian buffers. The main goal of our study is to extract and analyze various parameters of the riparian buffers of up to 12,000 km of river in southern Belgium (Wallonia) from three-dimensional (3D) point clouds based on LiDAR and photogrammetric surveys to i) map riparian buffers parameters on different scales, ii) interpret the regional patterns of the riparian buffers and iii) propose new riparian buffer management indicators. We propose different strategies to synthesize and visualize relevant information at different spatial scales ranging from local (<10 km) to regional scale (>12,000 km). Our results showed that the selected parameters had a clear regional pattern. The reaches of Ardenne ecoregion have channels with the highest flow widths and shallowest depths. In contrast, the reaches of the Loam ecoregion have the narrowest and deepest flow channels. Regional variability in channel width and depth is used to locate management units potentially affected by human impact. Riparian forest of the Loam ecoregion is characterized by the lowest longitudinal continuity and mean tree height, underlining significant human disturbance. As the availability of 3D point clouds at the regional scale is constantly growing, our study proposes reproducible methods which can be integrated into regional monitoring by land managers. With LiDAR still being relatively expensive to acquire, the use of photogrammetric point clouds combined with LiDAR data is a cost-effective means to update the characterization of the riparian forest conditions. [less ▲]

Detailed reference viewed: 61 (20 ULiège)
Full Text
Peer Reviewed
See detailA coupled electro-thermal Discontinuous Galerkin method
Homsi, Lina ULiege; Geuzaine, Christophe ULiege; Noels, Ludovic ULiege

in Journal of Computational Physics (2017), 348

This paper presents a Discontinuous Galerkin scheme in order to solve the nonlinear elliptic partial differential equations of coupled electro-thermal problems. In this paper we discuss the fundamental ... [more ▼]

This paper presents a Discontinuous Galerkin scheme in order to solve the nonlinear elliptic partial differential equations of coupled electro-thermal problems. In this paper we discuss the fundamental equations for the transport of electricity and heat, in terms of macroscopic variables such as temperature and electric potential. A fully coupled nonlinear weak formulation for electro-thermal problems is developed based on continuum mechanics equations expressed in terms of energetically conjugated pair of fluxes and fields gradients. The weak form can thus be formulated as a Discontinuous Galerkin method. The existence and uniqueness of the weak form solution are proved. The numerical properties of the nonlinear elliptic problems i.e., consistency and stability, are demonstrated under specific conditions, i.e. use of high enough stabilization parameter and at least quadratic polynomial approximations. Moreover the prior error estimates in the H1-norm and in the L2-norm are shown to be optimal in the mesh size with the polynomial approximation degree. [less ▲]

Detailed reference viewed: 59 (14 ULiège)
Full Text
Peer Reviewed
See detailEvaluation of adaptive facades: The case study of Al Bahr Towers in the UAE
Attia, Shady ULiege

in Shaping Qatar’s Sustainable Built Environment (2017), 2(6), 1-13

The assessment of adaptive facades presents a barrier as there is no established assessment technique. Many of the available facade performance evaluation systems or frameworks have limited applicability ... [more ▼]

The assessment of adaptive facades presents a barrier as there is no established assessment technique. Many of the available facade performance evaluation systems or frameworks have limited applicability for such advanced building facades. The complexity of adaptive or dynamic facades’ evaluation is related to the performance evaluation of facade elements, systems, and overall building performance coupled with occupant behavior and occupant satisfaction. In this context, this paper presents a case study of an adaptive sunscreen facade and evaluation of its performance and occupant behavior. The evaluation mainly focuses on pre- and post-construction phases of adaptive facades: the design assist phase (including the durability test, visual mockup, onsite mashrabiya mounting, and weather stripping), the commissioning phase (field verification and performance testing), and the monitoring phase. The selected project is a 150-meter-high twin tower that stands with a honeycombinspired structure and automated dynamic solar screen that responds to the sun’s movement. These solar screens respond dynamically and automatically to the angle of the sun, which improves the control over energy consumption, solar radiation, and glare with the ability to allow natural light into the building. This paper is part of the research activities of working group 3 of the European COST Action 1403 on “Adaptive Facades”. Different methods were used for evaluation and these include the following: interviews with the architect, facade engineer, technical control specialist and occupants, reviews of standards and codes, review of energy models, and a systematic design process mapping. A documentation of the case study describing the post-construction occupant comfort and facade operation was prepared. This paper’s audience comprises mainly project managers, architects, and building facade engineers together with facility managers who are concerned with the process of design, construction, and operation of adaptive sunscreens facades. The outcome of this study identifies quantifiable performance indicators and effective strategies for the design and performance evaluation of optimal adaptive facades. [less ▲]

Detailed reference viewed: 213 (4 ULiège)
Full Text
See detailLes Amis de la Conférence Mondiale des Humanités
Winand, Jean ULiege

Speech/Talk (2017)

Detailed reference viewed: 24 (1 ULiège)
See detailUp and downs of a magnetic oblique rotator viewed at high resolution
Nazé, Yaël ULiege; Zhekov, S. A.; Ud-Doula, A.

in The Lives and Death-Throes of Massive Stars (2017, November 01)

In 2006, the Of?p star HD191612 became the second O-star where a magnetic field was discovered. It provided a benchmark to understand the Of?p phenomenon as a whole. Ten years later, an X-ray monitoring ... [more ▼]

In 2006, the Of?p star HD191612 became the second O-star where a magnetic field was discovered. It provided a benchmark to understand the Of?p phenomenon as a whole. Ten years later, an X-ray monitoring performed at high-resolution reveals the behaviour of the hottest magnetospheric plasma: it is located at ~ 2R [SUB]⊙[/SUB], hot but not extreme (log(T) ~ 7), producing unshifted lines, and displaying a very repetitive variability. A direct comparison with simulations yields an overall good agreement, with only a few further improvements needed. [less ▲]

Detailed reference viewed: 5 (1 ULiège)
See detailThe supergiant O + O binary system HD 166734: a new study
Gosset, Eric ULiege; Mahy, Laurent ULiege; Damerdji, Yassine ULiege et al

in The Lives and Death-Throes of Massive Stars (2017, November 01)

We present here a modern study of the radial velocity curve and of the photometric light curve of the very interesting supergiant O7.5If + O9I(f) binary system HD 166734. The physical parameters of the ... [more ▼]

We present here a modern study of the radial velocity curve and of the photometric light curve of the very interesting supergiant O7.5If + O9I(f) binary system HD 166734. The physical parameters of the stars and the orbital parameters are carefully determined. We also perform the analysis of the observed X-ray light curve of this colliding-wind binary. [less ▲]

Detailed reference viewed: 10 (4 ULiège)
See detailInvestigating the Magnetospheres of Rapidly Rotating B-type Stars
Fletcher, C. L.; Petit, V.; Nazé, Yaël ULiege et al

in The Lives and Death-Throes of Massive Stars (2017, November 01)

Recent spectropolarimetric surveys of bright, hot stars have found that ~10% of OB-type stars contain strong (mostly dipolar) surface magnetic fields (~kG). The prominent paradigm describing the ... [more ▼]

Recent spectropolarimetric surveys of bright, hot stars have found that ~10% of OB-type stars contain strong (mostly dipolar) surface magnetic fields (~kG). The prominent paradigm describing the interaction between the stellar winds and the surface magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the stellar wind plasma is forced to move along the closed field loops of the magnetic field, colliding at the magnetic equator, and creating a shock. As the shocked material cools radiatively it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and characterizing the hot wind material confined by the magnetic fields of these stars. Some B-type stars are found to have very short rotational periods. The effects of the rapid rotation on the X-ray production within the magnetosphere have yet to be explored in detail. The added centrifugal force due to rapid rotation is predicted to cause faster wind outflows along the field lines, leading to higher shock temperatures and harder X-rays. However, this is not observed in all rapidly rotating magnetic B-type stars. In order to address this from a theoretical point of view, we use the X-ray Analytical Dynamical Magnetosphere (XADM) model, originally developed for slow rotators, with an implementation of new rapid rotational physics. Using X-ray spectroscopy from ESA's XMM-Newton space telescope, we observed 5 rapidly rotating B-types stars to add to the previous list of observations. Comparing the observed X-ray luminosity and hardness ratio to that predicted by the XADM allows us to determine the role the added centrifugal force plays in the magnetospheric X-ray emission of these stars. [less ▲]

Detailed reference viewed: 8 (1 ULiège)
See detailX-rays from colliding winds in massive binaries
Nazé, Yaël ULiege; Rauw, Grégor ULiege

in The Lives and Death-Throes of Massive Stars (2017, November 01)

In a massive binary, the strong shock between the stellar winds may lead to the generation of bright X-ray emission. While this phenomenon was detected decades ago, the detailed study of this emission was ... [more ▼]

In a massive binary, the strong shock between the stellar winds may lead to the generation of bright X-ray emission. While this phenomenon was detected decades ago, the detailed study of this emission was only made possible by the current generation of X-ray observatories. Through dedicated monitoring and observations at high resolution, unprecedented information was revealed, putting strong constraints on the amount and structure of stellar mass-loss. [less ▲]

Detailed reference viewed: 7 (1 ULiège)
Full Text
See detailArpenter l’Histoire pour mieux maîtriser la temporalité de l’histoire en classe du secondaire. Etude de cas (2013-2015) et programme de recherche (2017-)
Jadoulle, Jean-Louis ULiege

Scientific conference (2017, November 01)

Cette étude de cas tente d’évaluer l’impact d’un dispositif d’enseignement sur la maitrise de la temporalité historienne ; ce dispositif est conçu sous la forme de parcours diachroniques successifs ou « ... [more ▼]

Cette étude de cas tente d’évaluer l’impact d’un dispositif d’enseignement sur la maitrise de la temporalité historienne ; ce dispositif est conçu sous la forme de parcours diachroniques successifs ou « parcours chronologiques emboités » (Jadoulle, 2008, 2015). Elle a été conduite en Belgique francophone avec un enseignant et compare, à deux années d’intervalle, la maitrise de la temporalité historienne par des élèves de 4e année (16 ans). Ceux-ci composent deux cohortes : la première a été évaluée en 2013 et avait bénéficié d’un mode d’enseignement chronologique de la période qui va de l’arrivée de Colomb en Amérique au Congrès de Vienne (1815) ; la seconde a été évaluée en 2015 et avait bénéficié d’un enseignement de cette même période, par le même professeur, mais sous la forme de plusieurs « parcours chronologiques emboités » , chacun de ces parcours faisant ensuite l’objet d’une mise en perspective synchronique avec les autres. Les résultats indiquent que le dispositif dit des « parcours chronologiques emboités » améliore la maitrise de la temporalité historienne. Ils améliorent en particulier la capacité à établir une succession ou une diachronie, à identifier des changements et des continuités et à repérer des synchronies. [less ▲]

Detailed reference viewed: 14 (3 ULiège)
Full Text
Peer Reviewed
See detailConstraining the geometry and kinematics of the quasar broad emission line region using gravitational microlensing. I. Models and simulations
Braibant, Lorraine ULiege; Hutsemekers, Damien ULiege; Sluse, Dominique ULiege et al

in Astronomy and Astrophysics (2017), 607

Recent studies have shown that line profile distortions are commonly observed in gravitationally lensed quasar spectra. Often attributed to microlensing differential magnification, line profile ... [more ▼]

Recent studies have shown that line profile distortions are commonly observed in gravitationally lensed quasar spectra. Often attributed to microlensing differential magnification, line profile distortions can provide information on the geometry and kinematics of the broad emission line region (BLR) in quasars. We investigate the effect of gravitational microlensing on quasar broad emission line profiles and their underlying continuum, combining the emission from simple representative BLR models with generic microlensing magnification maps. Specifically, we considered Keplerian disk, polar, and equatorial wind BLR models of various sizes. The effect of microlensing has been quantified with four observables: μ[SUP]BLR[/SUP], the total magnification of the broad emission line; μ[SUP]cont[/SUP], the magnification of the underlying continuum; as well as red/blue, RBI and wings/core, WCI, indices that characterize the line profile distortions. The simulations showed that distortions of line profiles, such as those recently observed in lensed quasars, can indeed be reproduced and attributed to the differential effect of microlensing on spatially separated regions of the BLR. While the magnification of the emission line μ[SUP]BLR[/SUP] sets an upper limit on the BLR size and, similarly, the magnification of the continuum μ[SUP]cont[/SUP] sets an upper limit on the size of the continuum source, the line profile distortions mainly depend on the BLR geometry and kinematics. We thus built (WCI,RBI) diagrams that can serve as diagnostic diagrams to discriminate between the various BLR models on the basis of quantitative measurements. It appears that a strong microlensing effect puts important constraints on the size of the BLR and on its distance to the high-magnification caustic. In that case, BLR models with different geometries and kinematics are more prone to produce distinctive line profile distortions for a limited number of caustic configurations, which facilitates their discrimination. When the microlensing effect is weak, there is a larger overlap between the characteristics of the line profile distortions produced by the different models, and constraints can only be derived on a statistical basis. [less ▲]

Detailed reference viewed: 25 (2 ULiège)