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Peer Reviewed
See detailNon-responsive generalized bacterial infection associated with systemic lupus erythematosus (SLE) in a Beauceron
Clercx, Cécile ULg; Mc Entee, Kathleen ULg; Gilbert, S. et al

in 7th ESVIM Meeting - Lyon - France (1997)

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See detailNon-Rigid Object Tracker Based On a Robust Combination of Parametric Active Contour and Point Distribution Model
Olszewska, Joanna; Mathes, Tom; De Vleeschouwer, Christophe et al

in Proceedings of the SPIE Conference on Visual Communication and Image Processing (2007)

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See detailNon-small cell lung cancer and health-related quality of life (HRQOL): Is baseline HRQOL of prognostic value for survival?
Bottomley, A.; Smit, E.; Efficace, F. et al

in Quality of Life Research (2005), 14(9), 20501013

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See detailNon-Standard economics and competition law
Sibony, Anne-Lise ULg

Conference (2009, November 26)

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See detailNon-starch polysaccharide-degrading enzymes alter the microbial community and the fermentation patterns of barley cultivars and wheat products in an in vitro model of the porcine gastrointestinal tract
Bindelle, Jérôme ULg; Pieper, Robert; Montoya, Carlos A. et al

in FEMS Microbiology Ecology (2011), 76

An in vitro experiment was carried out to assess how non-starch polysaccharide (NSP)-degrading enzymes influence fermentation of dietary fibre in the pig large intestine. Seven wheat and barley products ... [more ▼]

An in vitro experiment was carried out to assess how non-starch polysaccharide (NSP)-degrading enzymes influence fermentation of dietary fibre in the pig large intestine. Seven wheat and barley products and cultivars with differing carbohydrate fractions (CHO) were hydrolyzed using pepsin and pancreatin in the presence or not of NSP-degrading enzymes (xylanase and b-glucanase) and the filter retentate fermented with sow fecal bacteria. Dry matter, starch, crude protein and β-glucan digestibilities during hydrolysis were measured. Fermentation kinetics of the hydrolyzed ingredients were modelled. Short-chain fatty acids (SCFA) production and molar ratio were compared after 12, 24 and 72 h. Microbial communities were analyzed after 72 h of fermentation using terminal restriction fragment length polymorphism (TRFLP). The results showed an increase of nutrient digestibility (P<0.001), whereas fermentability and SCFA production decreased (P<0.001) with addition of the enzyme. SCFA and bacterial community profiles indicated also a shift from propionate to acetate and an increase in cellulolytic Ruminoccocus- and xylanolytic Clostridium-like bacteria. This is explained by the increase in slowly fermentable insoluble CHO and the lower proportion of rapidly fermentable β-glucan and starch in the retentate when grains were incubated with NSP-degrading enzymes. Shifts were also different for the 4 barley varieties investigated, showing that the efficiency of the enzymes depends on the structure of the CHO fractions in cereal products and cultivars. [less ▲]

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See detailNon-stationnarite et aspects fonctionnels du comportement agonistique chez Tilapia macrochir (Boulenger 1912) (Piscer: Cichlidae)
Balthazart, Jacques ULg

in Acta Zoologica et Pathologica Antverpiensia (1974), 58(0), 29-40

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See detailNon-symbiotic hemoglobin-2 leads to an elevated energy state and to a combined increase in polyunsaturated fatty acids and total oil content when over-expressed in developing seeds of transgenic Arabidopsis plants.
Vigeolas, Hélène ULg; Huhn, D.; Geigenberger, P.

in Plant Physiology (2011)

Non-symbiotic hemoglobins are ubiquitously expressed in plants and divided into two different classes based on gene-expression pattern and oxygen binding-properties. Most of the published research has ... [more ▼]

Non-symbiotic hemoglobins are ubiquitously expressed in plants and divided into two different classes based on gene-expression pattern and oxygen binding-properties. Most of the published research has been on the function of class-1 hemoglobins. To investigate the role of class-2 hemoglobins, transgenic Arabidopsis plants were generated over-expressing Arabidopsis hemoglobin-2 (AHb2) under the control of a seed-specific promoter. Over-expression of AHb2 led to a 40% increase in the total fatty acid content of developing and mature seeds in three subsequent generations. This was mainly due to an increase in the poly-unsaturated C18:2 (omega-6) linoleic and C18:3 (omega-3) alpha-linolenic acids. Moreover, AHb2 over-expression led to an increase in the C18:2/C18:1 and C18:3/C18:2 ratios as well as in the C18:3 content in mol% of total fatty acids and in the unsaturation/saturation index of total seed lipids. The increase in fatty-acid content was mainly due to a stimulation of the rate of triacylglycerol synthesis which was attributable to a 3-fold higher energy state and a 2-fold higher sucrose content of the seeds. Under low external oxygen, AHb2 over-expression maintained an up to 5-fold higher energy state and prevented fermentation. This is consistent with AHb2 over-expression results in improved oxygen availability within developing seeds. In contrast to this, over-expression of class-1 hemoglobin did not lead to any significant increase in the metabolic performance of the seeds. Results provide evidence for a specific function of class-2 hemoglobin in seed oil production and in promoting the accumulation of poly-unsaturated fatty acids by facilitating oxygen supply in developing seeds. [less ▲]

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See detailNon-symmetrically substituted phenoxazinones from laccase-mediated oxidative cross-coupling of aminophenols: an experimental and theoretical insight
Bruyneel, Frédéric; Dive, Georges ULg; Marchand-Brynaert, Jacqueline

in Organic & Biomolecular Chemistry (2012), 10

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See detailNon-synoptic versus pseudo-synoptic data sets: an assimilation experiment
Rixen, Michel; Allen, J. T.; Beckers, Jean-Marie ULg

in Journal of Marine Systems (2001), 29(1-4), 313-333

Several first-order correction methods are implemented to compute pseudo-synoptic data sets from non-synoptic raw data sets. These include a geostrophic relocation method, a linear and a quadratic ... [more ▼]

Several first-order correction methods are implemented to compute pseudo-synoptic data sets from non-synoptic raw data sets. These include a geostrophic relocation method, a linear and a quadratic interpolation method, and a method using spatio-temporal correlation functions. The relocation method involves analyses and geostrophic velocity computations to allow the relocation of stations in time and space to a particular analysis time. Interpolation methods involve several almost identical and consecutive surveys interpolated in time. Temporal weighting methods are based upon a spatio-temporal function modifying the weight on data with respect to the time at which they have been sampled. These techniques are tested on the OMEGA data set and are validated by simple nudging assimilation into a 3D primitive equation model (PE). It is shown that, under certain hypothesis, these methods are able to correct the lack of synopticity in hydrographic data sets, and improve the diagnosis of vertical velocities computed from the Omega equation. These methods are of particular interest for the scientific community. They might be used together with diagnostic models. They might provide suitable pseudo-synoptic fields required by 3D PE models as initial conditions, boundary conditions or assimilation data sets. They may also be useful in the design of mesoscale samplings. (C) 2001 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailNon-territorial Macaques Can Range Like Territorial Gibbons When Partially Provisioned With Food
José Dominguez, Juan Manuel; Huynen, Marie-Claude ULg; Garcia, Carmen J et al

in Biotropica (2015)

Human food supplementation can affect components of animal socioecology by altering the abundance and distribution of available food. We studied the effect of food supplementation by comparing the ranging ... [more ▼]

Human food supplementation can affect components of animal socioecology by altering the abundance and distribution of available food. We studied the effect of food supplementation by comparing the ranging patterns and intergroup interactions of two groups of northern pigtailed macaques (Macaca leonina), a non-territorial primate species. One group was partially reliant on food provisioning, whereas the other group foraged wild food. We also compared the macaques’ movement with that of a group of white-handed gibbons (Hylobates lar), a territorial species inhabiting the same site. Home range, core area, and daily path lengths were significantly smaller for the semi-provisioned group than for the wild-feeding group. In contrast to wild-feeding macaques, supplemented macaques showed higher fidelity to home range, core area, and particularly to the region where human food was most accessible and abundant. The rela- tionship of daily path length and home range indicated a low defendability index for wild-feeding macaques; the higher index for the semi-provisioned group was consistent with the territorial pattern found in gibbons. Semi-provisioned macaques showed further traits of territoriality with aggression during intergroup encounters. These findings indicate that human modification of food availability can sig- nificantly affect movement patterns and intergroup competition in macaques. The observed ranging dynamics related to food provision- ing may decrease the efficiency of macaques as seed dispersers and increase predation on their home range, and thus have important consequences for plant regeneration and animal diversity. [less ▲]

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See detailNon-thermal emission from early-type binaries
Rauw, Grégor ULg

in Cosmic Gamma-Ray Sources (2004)

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See detailNon-thermal emission processes in massive binaries
De Becker, Michaël ULg

in Astronomy and Astrophysics Review (2007), 14(3-4), 171-216

In this paper, I present a general discussion of several astrophysical processes likely to play a role in the production of non-thermal emission in massive stars, with emphasis on massive binaries. Even ... [more ▼]

In this paper, I present a general discussion of several astrophysical processes likely to play a role in the production of non-thermal emission in massive stars, with emphasis on massive binaries. Even though the discussion will start in the radio domain where the non-thermal emission was first detected, the census of physical processes involved in the non-thermal emission from massive stars shows that many spectral domains are concerned, from the radio to the very high energies. First, the theoretical aspects of the non-thermal emission from early-type stars will be addressed. The main topics that will be discussed are respectively the physics of individual stellar winds and their interaction in binary systems, the acceleration of relativistic electrons, the magnetic field of massive stars, and finally the non-thermal emission processes relevant to the case of massive stars. Second, this general qualitative discussion will be followed by a more quantitative one, devoted to the most probable scenario where non-thermal radio emitters are massive binaries. I will show how several stellar, wind and orbital parameters can be combined in order to make some semi-quantitative predictions on the high-energy counterpart to the non-thermal emission detected in the radio domain. These theoretical considerations will be followed by a census of results obtained so far, and related to this topic. These results concern the radio, the visible, the X-ray and the gamma-ray domains. Prospects for the very high energy gamma-ray emission from massive stars will also be addressed. Two particularly interesting examples-one O-type and one Wolf-Rayet binary-will be considered in details. Finally, strategies for future developments in this field will be discussed. [less ▲]

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See detailNon-thermal Hard X-ray Emission from Colliding Wind Binary Systems
Khangulyan, Dmitry; Bosch-Ramon, Valenti; De Becker, Michaël ULg

Poster (2012, July)

Colliding-wind massive star binaries are known to produce strong shocks in their wind-wind interaction regions. The interaction region is the scenario of several physical processes, including strong ... [more ▼]

Colliding-wind massive star binaries are known to produce strong shocks in their wind-wind interaction regions. The interaction region is the scenario of several physical processes, including strong thermal X-ray emission and in several cases particle acceleration up to relativistic energies. The latter process is still poorly understood in these environments, and deserves a particular attention in stellar astrophysics. The investigation of particle acceleration is a critical aspect of high-energy astrophysics, especially at energies above 10 keV where non-thermal emission processes dominate. We discuss the possibility to detect the hard X-ray emission from WR147, a well-known particle accelerator, using Astro-H Hard X-ray Telescope (HXT) and Soft Gamma-Ray Detector (SGD), and to probe the particle acceleration process at work in its colliding-wind region. [less ▲]

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See detailNon-thermal processes in colliding-wind massive binaries: the contribution of Simbol-X to a multiwavelength investigation
De Becker, Michaël ULg; Blomme, Ronny; Micela, Giusi et al

in AIP Conference Proceedings (2009, May), 1126

Several colliding-wind massive binaries are known to be non-thermal emitters in the radio domain. This constitutes strong evidence for the fact that an efficient particle acceleration process is at work ... [more ▼]

Several colliding-wind massive binaries are known to be non-thermal emitters in the radio domain. This constitutes strong evidence for the fact that an efficient particle acceleration process is at work in these objects. The acceleration mechanism is most probably the Diffusive Shock Acceleration (DSA) process in the presence of strong hydrodynamic shocks due to the colliding-winds. In order to investigate the physics of this particle acceleration, we initiated a multiwavelength campaign covering a large part of the electromagnetic spectrum. In this context, the detailed study of the hard X-ray emission from these sources in the SIMBOL-X bandpass constitutes a crucial element in order to probe this still poorly known topic of astrophysics. It should be noted that colliding-wind massive binaries should be considered as very valuable targets for the investigation of particle acceleration in a similar way as supernova remnants, but in a different region of the parameter space. [less ▲]

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See detailNon-thermal radiation from a runaway early-type star
del Valle, M.; Romero, G.E.; De Becker, Michaël ULg

in AIP Conference Proceedings (2012, December), 1505

HD 195592 is an O-type supergiant star, known as a well-established runaway. Recently, a Fermi γ-ray source (2FGL J2030.7+4417) with a position compatible with that of HD 195592 has been reported. Our ... [more ▼]

HD 195592 is an O-type supergiant star, known as a well-established runaway. Recently, a Fermi γ-ray source (2FGL J2030.7+4417) with a position compatible with that of HD 195592 has been reported. Our goal is to explore a scenario where HD 195592 is the counterpart of the Fermi γ-ray source. The high-energy emission would be inverse Compton radiation produced in the bowshock of the runaway star. We calculate relativistic particle energy losses and the resulting radiation from the bowshock of HD 195592 and show that the latter is compatible with the detected γ-ray emission. We conclude that the Fermi source 2FGL J2030.7+4417 might be produced, under some energetic assumptions, by inverse Compton up-scattering of infrared photons from locally heated dust. HD 195592 might therefore be the very first object detected belonging to the category of γ-ray emitting runaway massive stars, whose existence has been recently predicted. [less ▲]

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See detailNon-thermal radio emission from colliding-wind binaries: modelling Cyg OB2 No. 8A and No. 9
Volpi, Delia; Blomme, Ronny; De Becker, Michaël ULg et al

in Neiner, Coralie; Wade, G.; Meynet, G. (Eds.) et al Active OB stars: structure, evolution, mass loss and critical limits (2011, July 01)

Some OB stars show variable non-thermal radio emission. The non-thermal emission is due to synchrotron radiation that is emitted by electrons accelerated to high energies. The electron acceleration occurs ... [more ▼]

Some OB stars show variable non-thermal radio emission. The non-thermal emission is due to synchrotron radiation that is emitted by electrons accelerated to high energies. The electron acceleration occurs at strong shocks created by the collision of radiatively-driven stellar winds in binary systems. Here we present results of our modelling of two colliding wind systems: Cyg OB2 No. 8A and Cyg OB2 No. 9. [less ▲]

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See detailNon-thermal radio emission from O-type stars. I. HD168112
Blomme, Ronny; Van Loo, S.; De Becker, Michaël ULg et al

in Astronomy and Astrophysics (2005), 436(3), 1033-1040

We present a radio lightcurve of the O5.5 III(f(+)) star HD 168112, based on archive data from the Very Large Array (VLA) and the Australia Telescope Compact Array (ATCA). The fluxes show considerable ... [more ▼]

We present a radio lightcurve of the O5.5 III(f(+)) star HD 168112, based on archive data from the Very Large Array (VLA) and the Australia Telescope Compact Array (ATCA). The fluxes show considerable variability and a negative spectral index, thereby confirming that HD 168112 is a non-thermal radio emitter. The non-thermal radio emission is believed to be due to synchrotron radiation from relativistic electrons that have been Fermi accelerated in shocks. For HD 168112, it is not known whether these shocks are due to a wind-wind collision in a binary system or to the intrinsic instability of the stellar wind driving mechanism. Assuming HD 168112 to be a single star, our synchrotron model shows that the velocity jump of the shocks should be very high, or there should be a very large number of shocks in the wind. Neither of these is compatible with time-dependent hydrodynamical calculations of O star winds. If, on the other hand, we assume that HD 168112 is a binary, the high velocity jump is easily explained by ascribing it to the wind-wind collision. By further assuming the star to be an eccentric binary, we can explain the observed radio variability by the colliding-wind region moving in and out of the region where free-free absorption is important. The radio data presented here show that the binary has a period of between one and two years. By combining the radio data with X-ray data, we find that the most likely period is similar to 1.4 yr. [less ▲]

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See detailNon-thermal radio emission from O-type stars. II. HD167971
Blomme, Ronny; De Becker, Michaël ULg; Runacres, M. C. et al

in Astronomy and Astrophysics (2007), 464(2), 701-148

HD 167971 is a triple system consisting of a 3.3-day eclipsing binary (O5- 8 V + O5- 8 V) and an O8 supergiant. It is also a well known non-thermal radio emitter. We observed the radio emission of HD ... [more ▼]

HD 167971 is a triple system consisting of a 3.3-day eclipsing binary (O5- 8 V + O5- 8 V) and an O8 supergiant. It is also a well known non-thermal radio emitter. We observed the radio emission of HD 167971 with the Very Large Array (VLA) and the Australia Telescope Compact Array (ATCA). By combining these data with VLA archive observations we constructed a radio lightcurve covering a 20-yr time-range. We searched for, but failed to find, the 3.3-day spectroscopic period of the binary in the radio data. This could be due to the absence of intrinsic synchrotron radiation in the colliding-wind region between the two components of the eclipsing binary, or due to the large amount of free-free absorption that blocks the synchrotron radiation. We are able to explain many of the observed characteristics of the radio data if the non-thermal emission is produced in a colliding-wind region between the supergiant and the combined winds of the binary. Furthermore, if the system is gravitationally bound, the orbital motion occurs over a period of similar to 20 years or longer, as suggested by the long-term variability in the radio data. We argue that the variability is due to the free-free absorption that changes with orbital phase or may also in part be due to changes in separation, should the orbit be eccentric. [less ▲]

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See detailNon-thermal radio emission from O-type stars. IV. Cygnus OB2 No. 8A
Blomme, R.; De Becker, Michaël ULg; Volpi, D. et al

in Astronomy and Astrophysics (2010), 519

Context. Several early-type colliding-wind binaries are known to emit synchrotron radiation due to relativistic electrons, which are most probably accelerated by the Fermi mechanism. By studying such ... [more ▼]

Context. Several early-type colliding-wind binaries are known to emit synchrotron radiation due to relativistic electrons, which are most probably accelerated by the Fermi mechanism. By studying such systems we can learn more about this mechanism, which is also relevant in other astrophysical contexts. Colliding-wind binaries are furthermore important for binary frequency determination in clusters and for understanding clumping and porosity in stellar winds. Aims: We study the non-thermal radio emission of the binary Cyg OB2 No. 8A, to see if it is variable and if that variability is locked to the orbital phase. We investigate if the synchrotron emission generated in the colliding-wind region of this binary can explain the observations and we verify that our proposed model is compatible with the X-ray data. Methods: We use both new and archive radio data from the Very Large Array (VLA) to construct a light curve as a function of orbital phase. We also present new X-ray data that allow us to improve the X-ray light curve. We develop a numerical model for the colliding-wind region and the synchrotron emission it generates. The model also includes free-free absorption and emission due to the stellar winds of both stars. In this way we construct artificial radio light curves and compare them with the observed one. Results: The observed radio fluxes show phase-locked variability. Our model can explain this variability because the synchrotron emitting region is not completely hidden by the free-free absorption. In order to obtain a better agreement for the phases of minimum and maximum flux we need to use stellar wind parameters for the binary components which are somewhat different from typical values for single stars. We verify that the change in stellar parameters does not influence the interpretation of the X-ray light curve. Our model has trouble explaining the observed radio spectral index. This could indicate the presence of clumping or porosity in the stellar wind, which - through its influence on both the Razin effect and the free-free absorption - can considerably influence the spectral index. Non-thermal radio emitters could therefore open a valuable pathway to investigate the difficult issue of clumping in stellar winds. [less ▲]

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See detailThe Non-thermal Radio Emitter HD 93250 Resolved by Long Baseline Interferometry
Sana, H.; Le Bouquin, J.-B.; De Becker, Michaël ULg et al

in Astrophysical Journal Letters (2011), 740

As the brightest O-type X-ray source in the Carina nebula, HD 93250 (O4 III(fc)) is X-ray overluminous for its spectral type and has an unusually hard X-ray spectrum. Two different scenarios have been ... [more ▼]

As the brightest O-type X-ray source in the Carina nebula, HD 93250 (O4 III(fc)) is X-ray overluminous for its spectral type and has an unusually hard X-ray spectrum. Two different scenarios have been invoked to explain its X-ray properties: wind-wind interaction and magnetic wind confinement. Yet, HD 93250 shows absolutely constant radial velocities over timescales of years suggesting either a single star, a binary system seen pole-on view or a very long period, and/or highly eccentric system. Using the ESO Very Large Telescope Interferometer, we resolved HD 93250 as a close pair with similar components. We measured a near-infrared flux ratio of 0.8 ± 0.1 and a separation of (1.5 ± 0.2) × 10-3 arcsec. At the distance of Carina, this corresponds to a projected physical distance of 3.5 AU. While a quantitative investigation would require a full characterization of the orbit, the binary nature of HD 93250 allows us to qualitatively explain both its X-ray flux and hardness and its non-thermal radio emission in the framework of a colliding wind scenario. We also discuss various observational biases. We show that, due to line blending of two similar spectral components, HD 93250 could have a period as short as 1 to several years despite the lack of measurable radial velocity variations. [less ▲]

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