References of "2012"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailFast core rotation in red-giant stars as revealed by gravity-dominated mixed modes
Beck, Paul G; Montalban Iglesias, Josefa ULg; Kallinger, Thomas et al

in Nature (2012), 481

When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much ... [more ▼]

When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much of the star's radius. Conservation of angular momentum requires that the cores of these stars rotate faster than their envelopes; indirect evidence supports this. Information about the angular-momentum distribution is inaccessible to direct observations, but it can be extracted from the effect of rotation on oscillation modes that probe the stellar interior. Here we report an increasing rotation rate from the surface of the star to the stellar core in the interiors of red giants, obtained using the rotational frequency splitting of recently detected `mixed modes'. By comparison with theoretical stellar models, we conclude that the core must rotate at least ten times faster than the surface. This observational result confirms the theoretical prediction of a steep gradient in the rotation profile towards the deep stellar interior. [less ▲]

Detailed reference viewed: 27 (8 ULg)
Full Text
Peer Reviewed
See detailAngular correlation functions of X-ray point-like sources in the full exposure XMM-LSS field
Elyiv, Andrii ULg; Clerc, N.; Plionis, M. et al

in Astronomy and Astrophysics (2012), 537

<BR /> Aims: Our aim is to study the large-scale structure of different types of AGN using the medium-deep XMM-LSS survey. <BR /> Methods: We measure the two-point angular correlation function of 5700 and ... [more ▼]

<BR /> Aims: Our aim is to study the large-scale structure of different types of AGN using the medium-deep XMM-LSS survey. <BR /> Methods: We measure the two-point angular correlation function of 5700 and 2500 X-ray point-like sources over the 11 sq. deg. XMM-LSS field in the soft (0.5-2 keV) and hard (2-10 keV) bands. For the conversion from the angular to the spatial correlation function we used the Limber integral equation and the luminosity-dependent density evolution model of the AGN X-ray luminosity function. <BR /> Results: We have found significant angular correlations with the power-law parameters γ = 1.81 ± 0.02, θ[SUB]0[/SUB] = 1.3'' ± 0.2'' for the soft, and γ = 2.00 ± 0.04, θ[SUB]0[/SUB] = 7.3'' ± 1.0'' for the hard bands. The amplitude of the correlation function w(θ) is higher in the hard than in the soft band for f[SUB]x[/SUB] ≲ 10[SUP]-14[/SUP] erg s[SUP]-1[/SUP] cm[SUP]-2[/SUP] and lower above this flux limit. We confirm that the clustering strength θ[SUB]0[/SUB] grows with the flux limit of the sample, a trend which is also present in the amplitude of the spatial correlation function, but only for the soft band. In the hard band, it remains almost constant with r[SUB]0[/SUB] ≃ 10h[SUP]-1[/SUP] Mpc, irrespective of the flux limit. Our analysis of AGN subsamples with different hardness ratios shows that the sources with a hard-spectrum are more clustered than soft-spectrum ones. This result may be a hint that the two main types of AGN populate different environments. Finally, we find that our clustering results correspond to an X-ray selected AGN bias factor of 2.5 for the soft band sources (at a median <inline-formula>bar{z} ≃ 1.1) and 3.3 for the hard band sources (at a median <inline-formula>bar{z} ≃ 1), which translates into a host dark matter halo mass of 10[SUP]13[/SUP]h[SUP]-1[/SUP]M[SUB]&sun;[/SUB] and 10[SUP]13.7[/SUP]h[SUP]-1[/SUP]M[SUB]&sun;[/SUB] for the soft and hard bands, respectively. This paper is dedicated to the memory of Olivier Garcet who has initiated the present work just before his sudden death. [less ▲]

Detailed reference viewed: 30 (6 ULg)
Full Text
See detailLow-Flow, Low-Gradient Severe Aortic Stenosis Despite Normal Ejection Fraction Is Associated With Severe Left Ventricular Dysfunction as Assessed by Speckle-Tracking Echocardiography: A Multicenter Study.
Adda, J.; Mielot, C.; Giorgi, R. et al

in Circulation: cardiovascular imaging (2012)

Background- Low-flow low-gradient (LFLG) is sometimes observed in severe aortic stenosis (AS) despite normal ejection fraction, but its frequency and mechanisms are still debated. We aimed to describe the ... [more ▼]

Background- Low-flow low-gradient (LFLG) is sometimes observed in severe aortic stenosis (AS) despite normal ejection fraction, but its frequency and mechanisms are still debated. We aimed to describe the characteristics of patients with LFLG AS and assess the presence of longitudinal left ventricular dysfunction in these patients. Methods and Results- In a multicenter prospective study, 340 consecutive patients with severe AS and normal ejection fraction were studied. Longitudinal left ventricular function was assessed by 2D-strain and global afterload by valvulo-arterial impedance. Patients were classified according to flow and gradient: low flow was defined as a stroke volume index ≤35 mL/m(2), low gradient as a mean gradient ≤40 mm Hg. Most patients (n=258, 75.9%) presented with high-gradient AS, and 82 patients (24.1%) with low-gradient AS. Among the latter, 52 (15.3%) presented with normal flow and low gradient and 30 (8.8%) with LFLG. As compared with normal flow and low gradient, patients with LFLG had more severe AS (aortic valve area=0.7±0.12 cm(2) versus 0.86±0.14 cm(2)), higher valvulo-arterial impedance (5.5±1.1 versus 4±0.8 mm Hg/mL/m(2)), and worse longitudinal left ventricular function (basal longitudinal strain=-11.6±3.4 versus -14.8±3%; P<0.001 for all). Conclusions- LFLG AS is observed in 9% of patients with severe AS and normal ejection fraction and is associated with high global afterload and reduced longitudinal systolic function. Patients with normal-flow low-gradient AS are more frequent and present with less severe AS, normal afterload, and less severe longitudinal dysfunction. Severe left ventricular longitudinal dysfunction is a new explanation to the concept of LFLG AS. [less ▲]

Detailed reference viewed: 24 (2 ULg)
Full Text
Peer Reviewed
See detailAssessing the accuracy of the surface gravity determination in late-type stars with solar-like pulsators
Morel, Thierry ULg; Miglio, Andrea ULg

in Monthly Notices of the Royal Astronomical Society (2012), 419

The frequency of maximum oscillation power measured in dwarfs and giants exhibiting solar-like pulsations provides a precise, and potentially accurate, inference of the stellar surface gravity. An ... [more ▼]

The frequency of maximum oscillation power measured in dwarfs and giants exhibiting solar-like pulsations provides a precise, and potentially accurate, inference of the stellar surface gravity. An extensive comparison for about 40 well-studied pulsating stars with gravities derived using classical methods (ionization balance, pressure-sensitive spectral features or location with respect to evolutionary tracks) supports the validity of this technique and reveals an overall remarkable agreement with mean differences not exceeding 0.05 dex (although with a dispersion of up to ˜0.2 dex). It is argued that interpolation in theoretical isochrones may be the most precise way of estimating the gravity by traditional means in nearby dwarfs. Attention is drawn to the usefulness of seismic targets as benchmarks in the context of large-scale surveys. [less ▲]

Detailed reference viewed: 22 (1 ULg)
Full Text
Peer Reviewed
See detailAsteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819
Miglio, A.; Brogaard, K.; Stello, D. et al

in Monthly Notices of the Royal Astronomical Society (2012), 419

Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G-K ... [more ▼]

Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G-K giants in open clusters with Kepler, we can now directly determine stellar masses for a statistically significant sample of stars in the old open clusters NGC 6791 and 6819. The aim of this work is to constrain the integrated RGB mass-loss by comparing the average mass of stars in the red clump (RC) with that of stars in the low-luminosity portion of the RGB [i.e. stars with L≲L(RC)]. Stellar masses were determined by combining the available seismic parameters ν[SUB]max[/SUB] and Δν with additional photometric constraints and with independent distance estimates. We measured the masses of 40 stars on the RGB and 19 in the RC of the old metal-rich cluster NGC 6791. We find that the difference between the average mass of RGB and RC stars is small, but significant [? (random) ±0.04 (systematic) M[SUB]&sun;[/SUB]]. Interestingly, such a small ? does not support scenarios of an extreme mass-loss for this metal-rich cluster. If we describe the mass-loss rate with Reimers prescription, a first comparison with isochrones suggests that the observed ? is compatible with a mass-loss efficiency parameter in the range 0.1 ≲η≲ 0.3. Less stringent constraints on the RGB mass-loss rate are set by the analysis of the ˜2 Gyr old NGC 6819, largely due to the lower mass-loss expected for this cluster, and to the lack of an independent and accurate distance determination. In the near future, additional constraints from frequencies of individual pulsation modes and spectroscopic effective temperatures will allow further stringent tests of the Δν and ν[SUB]max[/SUB] scaling relations, which provide a novel, and potentially very accurate, means of determining stellar radii and masses. [less ▲]

Detailed reference viewed: 17 (2 ULg)
Full Text
Peer Reviewed
See detailThe spectral variability and magnetic field characteristics of the Of?p star HD 148937
Wade, G. A.; Grunhut, J.; Gräfener, G. et al

in Monthly Notices of the Royal Astronomical Society (2012), 419

We report magnetic and spectroscopic observations and modelling of the Of?p star HD 148937 within the context of the Magnetism in Massive Stars (MiMeS) Large Program at the Canada-France-Hawaii Telescope ... [more ▼]

We report magnetic and spectroscopic observations and modelling of the Of?p star HD 148937 within the context of the Magnetism in Massive Stars (MiMeS) Large Program at the Canada-France-Hawaii Telescope. 32 high signal-to-noise ratio circularly polarized (Stokes V) spectra and 13 unpolarized (Stokes I) spectra of HD 148937 were acquired in 2009 and 2010. A definite detection of a Stokes V Zeeman signature is obtained in the grand mean of all observations [in both least-squares deconvolved (LSD) mean profiles and individual spectral lines]. The longitudinal magnetic field inferred from the Stokes V LSD profiles is consistently negative, in contrast to the essentially zero field strength measured from the diagnostic null profiles. A period search of new and archival equivalent width measurements confirms the previously reported 7.03 d variability period. The variation of equivalent widths is not strictly periodic: we present evidence for evolution of the amount or distribution of circumstellar plasma. Interpreting the 7.03 d period as the stellar rotational period within the context of the oblique rotator paradigm, we have phased the equivalent widths and longitudinal field measurements. The longitudinal field measurements show a weak sinusoidal variation of constant sign, with extrema out of phase with the Hα variation by about 0.25 cycles. From our constraint on v sin i≤ 45 km s[SUP]-1[/SUP], we infer that the rotational axis inclination i≤ 30°. Modelling the longitudinal field phase variation directly, we obtain the magnetic obliquity β= 38[SUP]+17[/SUP][SUB]-28[/SUB]° and dipole polar intensity B[SUB]d[/SUB]= 1020[SUP]-380[/SUP][SUB]+310[/SUB] G. Simple modelling of the Hα equivalent width variation supports the derived geometry. The inferred magnetic configuration confirms the suggestion of Nazé et al., who proposed that the weaker variability of HD 148937 as compared to other members of this class is a consequence of the stellar geometry. Based on the derived magnetic properties and published wind characteristics, we find a wind magnetic confinement parameter η[SUB]*[/SUB]≃ 20 and rotation parameter W= 0.12, supporting a picture in which the Hα emission and other line variability have their origin in an oblique, rigidly rotating magnetospheric structure resulting from a magnetically channelled wind. [less ▲]

Detailed reference viewed: 23 (0 ULg)
See detail(G)astronomie - Comète glacée
Nazé, Yaël ULg

Article for general public (2012)

Detailed reference viewed: 18 (2 ULg)
Full Text
Peer Reviewed
See detailImmune Reconstitution Inflammatory Syndrome in Natalizumab-Associated PML
Phan-Ba, Rémy ULg; LOMMERS, Emilie ULg; Moonen, Gustave ULg et al

in Neurology (2012), 78(1), 73

Detailed reference viewed: 46 (16 ULg)
Full Text
Peer Reviewed
See detailThe adapted augmented Lagrangian method: a new method for the resolution of the mechanical frictional contact problem
Bussetta, Philippe ULg; Daniel, Marceau; Ponthot, Jean-Philippe ULg

in Computational Mechanics (2012), 49(2), 259-275

The aim of this work is to propose a new numerical method for solving the mechanical frictional contact problem in the general case of multi-bodies in a three dimensional space. This method is called ... [more ▼]

The aim of this work is to propose a new numerical method for solving the mechanical frictional contact problem in the general case of multi-bodies in a three dimensional space. This method is called adapted augmented Lagrangian method (AALM) and can be used in a multi-physical context (like thermo-electro-mechanical fields problems). This paper presents this new method and its advantages over other classical methods such as penalty method (PM), adapted penalty method (APM) and, augmented Lagrangian method (ALM). In addition, the efficiency and the reliability of the AALM are proved with some academic problems and an industrial thermo-electromechanical problem. [less ▲]

Detailed reference viewed: 73 (34 ULg)
Full Text
Peer Reviewed
See detailRho proteins crosstalk via RhoGDIalpha
Stultiens, Audrey ULg; HO, Thi Thanh Giang ULg; Nusgens, Betty ULg et al

in Communicative & Integrative Biology (2012), 5(1), 99-101

Detailed reference viewed: 45 (19 ULg)
Full Text
See detailInternet-Based Investing at the Edge of Chaos
Choffray, Jean-Marie ULg

E-print/Working paper (2012)

This paper presents a simple, seven-step approach, to surviving on World Street: an investment environment characterized by high frequency trading system; over leveraged shadow entities and hedge funds ... [more ▼]

This paper presents a simple, seven-step approach, to surviving on World Street: an investment environment characterized by high frequency trading system; over leveraged shadow entities and hedge funds; flash crashes, incompetent management, reverse merger frauds, dot bubble 2.0 IPOs and stealth central banks’ actions. Its goal is to help you design efficient investment strategies while protecting your assets. It is based on a personal research conducted over the last ten years, involving hundreds of observations, investment simulations and actual decisions. [less ▲]

Detailed reference viewed: 378 (45 ULg)
Full Text
See detailMeasuring Downside and Extreme Risk Allocation in Equity Hedge Funds
Lambert, Marie ULg

E-print/Working paper (2012)

Detailed reference viewed: 39 (9 ULg)
Full Text
See detailMultilocus-based phylogeny and species recognition within the cosmopolitan Peltigera neopolydactyla-dolichorhiza complex
Magain, Nicolas ULg; Miadlikowska, Jolanta; Lutzoni, François et al

Poster (2012, January)

The Peltigera neopolydactyla/dolichorhiza complex is broadly distributed, growing in boreal and temperate regions from northern Norway to southern Chile, as well as in tropical mountains. Observed ... [more ▼]

The Peltigera neopolydactyla/dolichorhiza complex is broadly distributed, growing in boreal and temperate regions from northern Norway to southern Chile, as well as in tropical mountains. Observed morphotype and chemotype variation within this complex suggested the presence of multiple undescribed species. We inferred the phylogeny of Peltigera section Polydactylon with a special focus on the Peltigera neopolydactyla/dolichorhiza complex to determine the full breadth of this species complex, and to assess if taxa from different parts of the worlds but with similar morphological features share a most recent common ancestor. About 525 ITS sequences representing 104 distinct haplotypes were generated for representatives of Peltigera section Polydactylon. We selected a representative of each broadly defined phylotype for which three protein-coding loci: RPB1.1, b-tubulin and EFT2.1 were sequenced. Each of the three protein coding loci provided equivalent or more resolution and support than the ITS locus. The greatest proportion of significantly supported nodes across the tree resulted from β-tubulin alone. Many specimens identified as P. neopolydactyla and P. dolichorhiza are placed outside of this species complex. As currently defined both species represent polyphyletic assemblages of taxa including several potentially undescribed species. Our phylogenies suggest the presence of putatively new species within several complexes across the section. [less ▲]

Detailed reference viewed: 96 (13 ULg)
Full Text
Peer Reviewed
See detailÉtienne Klein, "Le Small Bang des nanotechnologies"
Thoreau, François ULg

in Esprit (Paris, France : 1932) (2012), 381

Detailed reference viewed: 63 (0 ULg)
Full Text
Peer Reviewed
See detailClaude Lévi-Strauss et les formes symboliques de la musique
Ledent, David ULg

in Homme (L') : Revue Française d'Anthropologie (2012), 201

Detailed reference viewed: 16 (1 ULg)
Full Text
Peer Reviewed
See detailIndividual decisions in placenta increta and percreta: a case series.
CHANTRAINE, Frédéric ULg; NISOLLE, Michelle ULg; PETIT, Philippe ULg et al

in Journal of Perinatal Medicine (2012), 40(3), 265-70

Abstract Objective: Placenta increta or percreta is an uncommon pathology, sometimes associated with high maternal morbidity. Its prevalence increases proportionally to the number of cesarean sections ... [more ▼]

Abstract Objective: Placenta increta or percreta is an uncommon pathology, sometimes associated with high maternal morbidity. Its prevalence increases proportionally to the number of cesarean sections. This study analyzed the changes of our management strategy to devise treatment guidelines for this uncommon disorder. Materials and methodology: Between 2005 and 2011, 10 cases of placenta increta or percreta were managed at our university hospital maternity department. Results: Among the 10 cases, seven were diagnosed prenatally. Two patients were diagnosed early, at 14 and 17 weeks of gestational age, and their pregnancies were terminated. Five had hysterectomies during the intrapartum period, and despite attempted conservative treatment for the two others, hysterectomy proved necessary 2 months postpartum because of intrauterine infections. Seven of the 10 women had hysterectomies. Conclusion: Prenatal diagnosis of placenta increta or percreta is essential to plan the delivery in a competent tertiary care center. The decision to perform a cesarean hysterectomy or leave the placenta in situ for spontaneous delivery is based on the extent of infiltration, the patient's hemodynamic status, and her desire to remain fertile. The high-risk of infection and severe hemorrhage must not be overlooked should conservative treatment be chosen. This situation requires prolonged close monitoring. [less ▲]

Detailed reference viewed: 88 (7 ULg)
See detailTitan airglow: FUV and EUV 2009 UVIS spectra of airglow during day, night and eclipse
Ajello, J.M.; Stevens, M.; West, R. et al

Conference (2012, January)

Detailed reference viewed: 2 (0 ULg)