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See detailRecent summer Arctic atmospheric circulation anomalies in a historical perspective
Belleflamme, Alexandre ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in Cryosphere (The) (2015), 9

A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and ... [more ▼]

A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500 hPa geopotential height data from five reanalysis data sets (ERA-Interim, ERA-40, NCEP/NCAR, ERA-20C, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 2007–2012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. For example, only ERA-20C shows circulation anomalies that could explain the 1920–1930 summertime Greenland warming, in contrast to 20CRv2. While the recent anomalies exceed by a factor of 2 the interannual variability of the atmospheric circulation of the Arctic region, their origin (natural variability or global warming) remains debatable. [less ▲]

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See detailContributions to combinatorics on words in an abelian context and covering problems in graphs
Vandomme, Elise ULg

Doctoral thesis (2015)

This thesis dissertation is divided into two (distinct but connected) parts that reflect the joint PhD. We study and we solve several questions regarding on the one hand combinatorics on words in an ... [more ▼]

This thesis dissertation is divided into two (distinct but connected) parts that reflect the joint PhD. We study and we solve several questions regarding on the one hand combinatorics on words in an abelian context and on the other hand covering problems in graphs. Each particular problem is the topic of a chapter. In combinatorics on words, the first problem considered focuses on the 2-regularity of sequences in the sense of Allouche and Shallit. We prove that a sequence satisfying a certain symmetry property is 2-regular. Then we apply this theorem to show that the 2-abelian complexity functions of the Thue--Morse word and the period-doubling word are 2-regular. The computation and arguments leading to these results fit into a quite general scheme that we hope can be used again to prove additional regularity results. The second question concerns the notion of return words up to abelian equivalence, introduced by Puzynina and Zamboni. We obtain a characterization of Sturmian words with non-zero intercept in terms of the finiteness of the set of abelian return words to all prefixes. We describe this set of abelian returns for the Fibonacci word but also for the Thue--Morse word (which is not Sturmian). We investigate the relationship existing between the abelian complexity and the finiteness of this set. In graph theory, the first problem considered deals with identifying codes in graphs. These codes were introduced by Karpovsky, Chakrabarty and Levitin to model fault-diagnosis in multiprocessor systems. The ratio between the optimal size of an identifying code and the optimal size of a fractional relaxation of an identifying code is between 1 and 2 ln(|V|)+1 where V is the vertex set of the graph. We focus on vertex-transitive graphs, since we can compute the exact fractional solution for them. We exhibit infinite families, called generalized quadrangles, of vertex-transitive graphs with integer and fractional identifying codes of order |V|^a with a in {1/4,1/3,2/5}. The second problem concerns (r,a,b)-covering codes of the infinite grid already studied by Axenovich and Puzynina. We introduce the notion of constant 2-labellings of weighted graphs and study them in four particular weighted cycles. We present a method to link these labellings with covering codes. Finally, we determine the precise values of the constants a and b of any (r,a,b)-covering code of the infinite grid with |a-b|>4. This is an extension of a theorem of Axenovich. [less ▲]

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See detailLa période hollandaise en Belgique
Brüll, Christoph ULg

Conference given outside the academic context (2015)

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See detailEnvironmental changes and the city
Ozer, Pierre ULg

Scientific conference (2015, January 06)

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See detailHigh-density mapping of the MHC identifies a shared role for HLA-DRB1*01:03 in inflammatory bowel diseases and heterozygous advantage in ulcerative colitis.
Goyette, Philippe; Boucher, Gabrielle; Mallon, D et al

in Nature Genetics (2015)

Genome-wide association studies of the related chronic inflammatory bowel diseases (IBD) known as Crohn's disease and ulcerative colitis have shown strong evidence of association to the major ... [more ▼]

Genome-wide association studies of the related chronic inflammatory bowel diseases (IBD) known as Crohn's disease and ulcerative colitis have shown strong evidence of association to the major histocompatibility complex (MHC). This region encodes a large number of immunological candidates, including the antigen-presenting classical human leukocyte antigen (HLA) molecules. Studies in IBD have indicated that multiple independent associations exist at HLA and non-HLA genes, but they have lacked the statistical power to define the architecture of association and causal alleles. To address this, we performed high-density SNP typing of the MHC in >32,000 individuals with IBD, implicating multiple HLA alleles, with a primary role for HLA-DRB1*01:03 in both Crohn's disease and ulcerative colitis. Noteworthy differences were observed between these diseases, including a predominant role for class II HLA variants and heterozygous advantage observed in ulcerative colitis, suggesting an important role of the adaptive immune response in the colonic environment in the pathogenesis of IBD. [less ▲]

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See detailIchtyofaune du bassin du fleuve Mono (Bénin et Togo): diversité, écologie et impacts anthropiques
Lederoun, Djiman ULg

Doctoral thesis (2015)

This study has three main objectives: (1) to obtain an inventory of the ichthyofauna of the Mono River that is as complete as possible; (2) to study the ecology of this ichthyofauna; and (3) to document ... [more ▼]

This study has three main objectives: (1) to obtain an inventory of the ichthyofauna of the Mono River that is as complete as possible; (2) to study the ecology of this ichthyofauna; and (3) to document the impact of fishing on the exploited stocks based on two targeted species. The inventory was made by compiling the literature, by studying collections of museums and of other institutions and by several sampling campaigns, conducted between February 2011 and March 2014. This resulted in an inventory of 91 fish species belonging to 67 genera, 42 families and 14 orders. The Perciformes (31 species), Siluriformes (18), Osteoglossiformes (10), Cypriniformes (9) and Characiformes (9) are the most diverse families in the Mono River Basin. The most species-rich families are the Cichlidae (9 espèces), Cyprinidae (9), Mormyridae (7), Clariidae (7) and Alestidae (6). Twenty-nine species, of which 7 of freshwater and 22 of marine or estuarine origin have been added to the ichtyofauna as known before this study. Nine species present in museum collections and three species only known from the literature have not been collected again. Several taxonomic problems have been encountered. Two of these cases were studied in depth. Foremost, the taxonomic status of Brycinus leuciscus and B. luteus (Alestiidae, Characiformes) was revised based on specimens originating from the complete distribution range of the two nominal species. This allowed us to synonymise the two species, with Brycinus leuciscus as senior synonym. The latter has been erroneously mentioned from the Mono River. Our results, however, confirmed the presence of two phenotypes, i.e. one with and one without a pre-dorsal hump, which was mentioned in the literature as intra-specific variation in B. leuciscus. A comparative study comparing specimens belonging to 'Barbus' nigeriensis (Cyprinidae, Cypriniformes) of the Mono Basin with those originating from the basins of the Volta, the Ogun et the Niger revealed the presence of a new species, described as Barbus "Vandewalle", a Volta Basin endemic. An indentification key of the different families, genera and species from the Mono Basin is presented. For the ecological study, two seasonal sampling campaigns were performed (from December to mid-March and from mid-July to mid-September) in 2012 and 2013 using gill nets of different mesh-size (10, 12, 17, 20 et 22 mm knot to knot). Sampling was performed at 10 sampling sites that were located upstream and downstream of the Adjarala Falls (the site of a planned hydroelectric plant, 100 km upstream of that of Nangbéto) and upstream and downstream of the dam at Nangbéto. Seventeen physico-chemical and environmental variables were taken at these sites. The ordination of the sampling sites in relation to their values for the physico-chemical, environmental variables and to their fish assemblages was studied using a non-linear method: the self organising map (SOM). The samples were scattered in four groups in function of their physico-chemical and environmental variables. The distance to the source, height of the canopy, rocks, coverage of the canopy, altitude, gravel, mud, sand, water velocity and dissolved oxygen were the most discriminating factors for the obtained groups. The zone of the Adjarala, where a new dam will be constructed, differs by its rocky substrate, the velocity of the water and the relatively high amount of dissolved oxygen. For the ichthyofauna, the SOM suggest a structuring in three groups. Our results oppose the tendency to homogeny in the middle course of rivers, which is probably due to the presence of the dam at Nangbéto. A significant correlation was found between the distribution of the species and the physico-chemical and environmental parameters. The distance to the source, altitude, forested river banks, height of the canopy, velocity of the water, conductivity, transparency and pH were the parameters that explained the distribution of the fish community best. The level of disturbance of the ecosystem, which was studied using the Abundance Biomass Comparison (ABC) showed that the zones at and near the dam at Nangbéto were the most stressed. A length-weight and length-length key was designed for the first time for the 37 species that were the most abundant in the catches. This was done in order to improve the quality of the fisheries statistics collected by fisheries officers on the scale of the basin. The analysis of the allometric coefficient b of the length-weight relation showed that the majority of the fishes had an allometric growth. The condition factor calculated in order to estimate the amount of flesh on the fish showed that the environment was heavily disturbed. To conclude, from the results of the study on the impact of the fisheries on targeted species, it became clear that the population of Sarotherodon melanotheron melanotheron is over-exploited at Lake Toho. At Lakes Doukon and Togbadji, on the other hand, an under-exploitation of the population of S. galilaeus galilaeus was observed. The latter illustrates the possibility of sustainable management even in the presence of intensive fishing pressure. As, in this thesis, several cases of anthropogenic impacts were identified, a regular surveillance programme will be paramount in order to preserve the ichthyological diversity of the Mono River Basin. [less ▲]

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See detailAssociation of Cerebrospinal Fluid Prion Protein Levels and the Distinction Between Alzheimer Disease and Creutzfeldt-Jakob Disease
Dorey, Aline; Tholance, Yannick; Vighetto, Alain et al

in JAMA Neurology (2015)

IMPORTANCE Although typical forms of Alzheimer disease (AD) and Creutzfeldt-Jakob disease (CJD) are clinically distinguishable, atypical AD phenotypesmay pose a diagnostic challenge. The major biological ... [more ▼]

IMPORTANCE Although typical forms of Alzheimer disease (AD) and Creutzfeldt-Jakob disease (CJD) are clinically distinguishable, atypical AD phenotypesmay pose a diagnostic challenge. The major biological diagnostic biomarker for identifying CJD, 14-3-3 protein in cerebrospinal fluid (CSF), unfortunately lacks specificity when confronting a rapid dementia presentation. OBJECTIVE To assess the relevance of total CSF prion protein (t-PrP) levels in the differential biological diagnosis between atypical AD phenotypes and CJD. DESIGN, SETTING, AND PARTICIPANTS A retrospective study in an autopsy-confirmed cohort of 82 patients was performed to evaluate the relevance of CSF t-PrP to distinguish 30 definite cases of AD from 52 definite cases of CJD. Next, CSF t-PrP concentration was measured in a cohort of 104 patients including 55 patients with probable AD, 26 with probable sporadic CJD, and 23 control patients for whom 14-3-3 protein, total tau, phosphorylated tau 181 (P-tau181), and Aβ1-42 were available.We investigated 46 patients diagnosed as having probable AD who presented atypical phenotypes. A diagnosis strategy was proposed to classify atypical AD phenotypes with suspicion of CJD based on a decision tree combining CSF biomarkers. MAIN OUTCOMES AND MEASURES We determined CSF t-PrP levels for all patients.We calculated the ratio of total tau and P-tau181 and determined the diagnostic accuracy of each biomarker alone or in combination.We calculated the misclassification rate for each biomarker that corresponded to the percentage of patients within the group of atypical AD phenotypes wrongly classified as CJD. RESULTS In patients with CJD, CSF t-PrP concentrations were decreased compared with control participants and patients with AD. When considering the differential diagnosis of CJD compared with atypical AD phenotypes, CSF t-PrP determination reached 82.1%sensitivity and 91.3%specificity. The misclassification rate of atypical AD phenotypes decreased from 43.5%, obtained when using the CSF 14-3-3 protein determination alone, to only 4.3%when calculating the ratio total tau/(P-tau181 × t-PrP). The proposed classification tree permitted correct classification of 98.4%of the patients. CONCLUSIONS AND RELEVANCE For unusual phenotypes of AD, especially cases presenting with a biological ambiguity suggesting CJD, determination of CSF t-PrP levels increased diagnostic accuracy. The use of CSF t-PrP levels may be beneficial in clinical practice in [less ▲]

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See detailEffect of stress path on the miniaturizatio size effect for nickel polycrystals
Keller, Clement; Hug, Eric; Duchene, Laurent ULg et al

Conference (2015, January 04)

The mechanical behavior of mettalic materials deeply depends on the size of samples. For specimen dimensions de creasing from a few millimeters to a few micrometers, the general observed trend is a ... [more ▼]

The mechanical behavior of mettalic materials deeply depends on the size of samples. For specimen dimensions de creasing from a few millimeters to a few micrometers, the general observed trend is a softening of the mechanical behavior in tension which affects the stress level and the strain hardening. This effect is triggered by the derease of the number of grains across the thickness ( also called thickness"t" over grain size "d" ratio). The objective of this work is to provide new experimental results in order to analyse the miniaturization size effects for various stress paths without strain gradients across the thickness of the samples. To this aim, experimental tensil tests, large tensile tests and shear tests have been performed on Ni sheets ( 0.5mm) with various grain sizes ensuring different t/d ratios. Results show that the miniaturization softening is affected by triaxiality, the larger is this parameter, the lower is the mechanicval softening. These features seem to be linked to surface effects which are larger for low triaxiality stress paths. Attempts of numerical simulations using strain gradient crystal plasticity model are also performed to confirm the role played by surface effects. [less ▲]

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See detailUpscaling of an electronic nose for continuously stirred tank reactor stability monitoring from pilot-scale to real-scale agricultural co-digestion biogas plant
Adam, Gilles ULg; Lemaigre, Sébastien; Goux, Xavier et al

in Bioresource Technology (2015), 178

This study investigated the use of an electronic nose for on-line anaerobic reactor state monitoring at the pilot-scale level and then upscaling to the full-scale level. E-nose indicator was compared to ... [more ▼]

This study investigated the use of an electronic nose for on-line anaerobic reactor state monitoring at the pilot-scale level and then upscaling to the full-scale level. E-nose indicator was compared to classical state indicators such as pH, alkalinity, volatile fatty acids concentration and to other gas phase compounds. Multivariate statistical process control method, based on principal component analysis and the Hotelling's T² statistics was used to derive an indicator representative of the reactor state. At the pilot-scale level, the e-nose indicator was relevant and could distinguish 3 process states: steady-state, transient and collapsing process. At the full-scale level, the e-nose indicator could provide the warning of the major disturbance whereas two slight disturbances were not detected and it gave one major false alarm. This work showed that gas phase relation with anaerobic process should be deeper investigated, as an e-nose could indicate the reactor state, focusing on the gas phase. [less ▲]

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See detailBasin-scale partitioning of Greenland ice sheet mass balance components (2007–2011)
Andersen, M.L.; Stenseng, L.; Skourup, H. et al

in Earth and Planetary Science Letters (2015), 409

The current deficit in Greenland ice sheet mass balance is due to both a decrease in surface mass balance (SMB ) input and an increase in ice discharge (D ) output. While SMB processes are beginning to be ... [more ▼]

The current deficit in Greenland ice sheet mass balance is due to both a decrease in surface mass balance (SMB ) input and an increase in ice discharge (D ) output. While SMB processes are beginning to be well captured by observationally-constrained climate modeling, insight into D is relatively limited. We use InSAR-derived velocities, in combination with ice thickness observations, to quantify the mass flux (F ) across a flux perimeter around the ice sheet at ∼1700 m elevation. To quantify D , we correct F for SMB , as well as changes in volume due to ice dynamics, in the area downstream of the gate. Using a 1961–1990 reference climatology SMB field from the MAR regional climate model, we quantify ice sheet mass balance within eighteen basins. We find a 2007–2011 mean D of View the MathML source. We find a 2007–2011 mean total mass balance of View the MathML source, which is equal to a 0.73 mm yr−1 global sea level rise contribution. This mass loss is dominated by SMB, which accounts for 61% of mass loss in the basins where partitioning is possible. [less ▲]

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See detailV444 Cygni X-ray and polarimetric variability: Radiative and Coriolis forces shape the wind collision region
Lomax, J. R.; Nazé, Yaël ULg; Hoffman, J. L. et al

in Astronomy and Astrophysics (2015), 573

We present results from a study of the eclipsing, colliding-wind binary V444 Cyg that uses a combination of X-ray and optical spectropolarimetric methods to describe the 3D nature of the shock and wind ... [more ▼]

We present results from a study of the eclipsing, colliding-wind binary V444 Cyg that uses a combination of X-ray and optical spectropolarimetric methods to describe the 3D nature of the shock and wind structure within the system. We have created the most complete X-ray light curve of V444 Cyg to date using 40 ks of new data from Swift, and 200 ks of new and archived XMM-Newton observations. In addition, we have characterized the intrinsic, polarimetric phase-dependent behavior of the strongest optical emission lines using data obtained with the University of Wisconsin's Half-Wave Spectropolarimeter. We have detected evidence of the Coriolis distortion of the wind-wind collision in the X-ray regime, which manifests itself through asymmetric behavior around the eclipses in the system's X-ray light curves. The large opening angle of the X-ray emitting region, as well as its location (i.e. the WN wind does not collide with the O star, but rather its wind) are evidence of radiative braking/inhibition occurring within the system. Additionally, the polarimetric results show evidence of the cavity the wind-wind collision region carves out of the Wolf-Rayet star's wind. [less ▲]

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See detailThe Gaia-ESO Survey: CNO abundances in the open clusters Trumpler 20, NGC 4815, and NGC 6705
Tautvaišienė, G.; Drazdauskas, A.; Mikolaitis, Š. et al

in Astronomy and Astrophysics (2015), 573

Context. The Gaia-ESO Public Spectroscopic Survey will observe a large sample of clusters and cluster stars, covering a wide age-distance-metallicity-position-density parameter space. <BR /> Aims: We aim ... [more ▼]

Context. The Gaia-ESO Public Spectroscopic Survey will observe a large sample of clusters and cluster stars, covering a wide age-distance-metallicity-position-density parameter space. <BR /> Aims: We aim to determine C, N, and O abundances in stars of Galactic open clusters of the Gaia-ESO survey and to compare the observed abundances with those predicted by current stellar and Galactic evolution models. In this pilot paper, we investigate the first three intermediate-age open clusters. <BR /> Methods: High-resolution spectra, observed with the FLAMES-UVES spectrograph on the ESO VLT, were analysed using a differential model atmosphere method. Abundances of carbon were derived using the C[SUB]2[/SUB] band heads at 5135 and 5635.5 Å. The wavelength interval 6470-6490 Å, with CN features, was analysed to determine nitrogen abundances. Oxygen abundances were determined from the [O i] line at 6300 Å. <BR /> Results: The mean values of the elemental abundances in Trumpler 20 as determined from 42 stars are: [ Fe/H ] = 0.10 ± 0.08 (s.d.), [ C/H ] = -0.10 ± 0.07, [ N/H ] = 0.50 ± 0.07, and consequently C/N = 0.98 ± 0.12. We measure from five giants in NGC 4815: [ Fe/H ] = -0.01 ± 0.04, [ C/H ] = -0.17 ± 0.08, [ N/H ] = 0.53 ± 0.07, [ O/H ] = 0.12 ± 0.09, and C/N = 0.79 ± 0.08. We obtain from 27 giants in NGC 6705: [ Fe/H ] = 0.0 ± 0.05, [ C/H ] = -0.08 ± 0.06, [ N/H ] = 0.61 ± 0.07, [ O/H ] = 0.13 ± 0.05, and C/N = 0.83 ± 0.19. The C/N ratios of stars in the investigated open clusters were compared with the ratios predicted by stellar evolutionary models. For the corresponding stellar turn-off masses from 1.9 to 3.3 M[SUB]⊙[/SUB], the observed C/N ratio values are very close to the predictions of standard first dredge-up models as well as to models of thermohaline extra-mixing. They are not decreased as much as predicted by the recent model in which the thermohaline- and rotation-induced extra-mixing act together. The average [O/H] abundance ratios of NGC 4815 and NGC 6705 are compared with the predictions of two Galactic chemical evolution models. The data are consistent with the evolution at the solar radius within the errors. <BR /> Conclusions: The first results of CNO determinations in open clusters show the potential of the Gaia-ESO Survey to judge stellar and Galactic chemical evolution models and the validity of their physical assumptions through a homogeneous and detailed spectral analysis. Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 188.B-3002 (The Gaia-ESO Public Spectroscopic Survey, PIs G. Gilmore and S. Randich). [less ▲]

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See detailFeature issue of digital holography and 3D imaging (DH): introduction
Hayasaki, Yoshio; Liu, Jung-Ping; Georges, Marc ULg

in Applied Optics (2015), 54(1), 1-2

The OSA Topical Meeting “Digital Holography and 3D Imaging (DH)” was held in Seattle, Washington, 13–17 July 2014. Feature issues based on the DH meeting series have been released by Applied Optics (AO ... [more ▼]

The OSA Topical Meeting “Digital Holography and 3D Imaging (DH)” was held in Seattle, Washington, 13–17 July 2014. Feature issues based on the DH meeting series have been released by Applied Optics (AO) since 2007. In this year (2014), Optics Express (OE) and AO jointly decided to have one such feature issue in each journal. The feature issue includes 27 papers and covers a large range of topics, reflecting the rapidly expanding techniques and applications of digital holography and 3D imaging. The DH meeting will continue in the future, as expected, and the next meeting is scheduled to be held on24–28 May 2015, at Shanghai Institute of Optics and Fine Mechanics, Shanghai, China. [less ▲]

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See detailForbidden oxygen lines at various nucleocentric distances in comets
Decock, Alice ULg; Jehin, Emmanuel ULg; Rousselot, P. et al

in Astronomy and Astrophysics (2015), 573

Aims: We study the formation of the [OI] lines - that is, 5577.339 Å (the green line), 6300.304 Å and 6363.776 Å (the two red lines) - in the coma of comets and determine the parent species of the oxygen ... [more ▼]

Aims: We study the formation of the [OI] lines - that is, 5577.339 Å (the green line), 6300.304 Å and 6363.776 Å (the two red lines) - in the coma of comets and determine the parent species of the oxygen atoms using the ratio of the green-to-red-doublet emission intensity, I[SUB]5577[/SUB]/(I[SUB]6300[/SUB] + I[SUB]6364[/SUB]), (hereafter the G/R ratio) and the line velocity widths. <BR /> Methods: We acquired high-resolution spectroscopic observations at the ESO Very Large Telescope of comets C/2002 T7 (LINEAR), 73P-C/Schwassmann-Wachmann 3, 8P/Tuttle, and 103P/Hartley 2 when they were close to Earth (<0.6 au). Using the observed spectra, which have a high spatial resolution (<60 km/pixel), we determined the intensities and widths of the three [OI] lines. We spatially extracted the spectra to achieve the best possible resolution of about 1-2'', that is, nucleocentric projected distances of 100 to 400 km depending on the geocentric distance of the comet. We decontaminated the [OI] green line from C[SUB]2[/SUB] lines blends that we identified. <BR /> Results: The observed G/R ratio in all four comets varies as a function of nucleocentric projected distance (between ~0.25 to ~0.05 within 1000 km). This is mainly due to the collisional quenching of O([SUP]1[/SUP]S) and O([SUP]1[/SUP]D) by water molecules in the inner coma. The observed green emission line width is about 2.5 km s[SUP]-1[/SUP] and decreases as the distance from the nucleus increases, which can be explained by the varying contribution of CO[SUB]2[/SUB] to the O([SUP]1[/SUP]S) production in the innermost coma. The photodissociation of CO[SUB]2[/SUB] molecules seem to produce O([SUP]1[/SUP]S) closer to the nucleus, while the water molecule forms all the O([SUP]1[/SUP]S) and O([SUP]1[/SUP]D) atoms beyond 10[SUP]3[/SUP] km. Thus we conclude that the main parent species producing O([SUP]1[/SUP]S) and O([SUP]1[/SUP]D) in the inner coma is not always the same. The observations have been interpreted in the framework of the previously described coupled-chemistry-emission model, and the upper limits of the relative abundances of CO[SUB]2[/SUB] were derived from the observed G/R ratios. Measuring the [OI] lines might provide a new way to determine the CO[SUB]2[/SUB] relative abundance in comets. Based on observations made with ESO Telescope at the La Silla Paranal Observatory under programs ID 073.C-0525, 277.C-5016, 080.C-0615 and 086.C-0958.Tables 3 and 4 are available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201424403/olm">http://www.aanda.org</A> [less ▲]

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See detailMonte Carlo Simulation of Metastable Oxygen Photochemistry in Cometary Atmospheres
Bisikalo, D. V.; Shematovich, V. I.; Gérard, Jean-Claude ULg et al

in The Astrophysical Journal (2015), 798

Cometary atmospheres are produced by the outgassing of material, mainly H[SUB]2[/SUB]O, CO, and CO[SUB]2[/SUB] from the nucleus of the comet under the energy input from the Sun. Subsequent photochemical ... [more ▼]

Cometary atmospheres are produced by the outgassing of material, mainly H[SUB]2[/SUB]O, CO, and CO[SUB]2[/SUB] from the nucleus of the comet under the energy input from the Sun. Subsequent photochemical processes lead to the production of other species generally absent from the nucleus, such as OH. Although all comets are different, they all have a highly rarefied atmosphere, which is an ideal environment for nonthermal photochemical processes to take place and influence the detailed state of the atmosphere. We develop a Monte Carlo model of the coma photochemistry. We compute the energy distribution functions (EDF) of the metastable O([SUP]1[/SUP]D) and O([SUP]1[/SUP]S) species and obtain the red (630 nm) and green (557.7 nm) spectral line shapes of the full coma, consistent with the computed EDFs and the expansion velocity. We show that both species have a severely non-Maxwellian EDF, that results in broad spectral lines and the suprathermal broadening dominates due to the expansion motion. We apply our model to the atmosphere of comet C/1996 B2 (Hyakutake) and 103P/Hartley 2. The computed width of the green line, expressed in terms of speed, is lower than that of the red line. This result is comparable to previous theoretical analyses, but in disagreement with observations. We explain that the spectral line shape does not only depend on the exothermicity of the photochemical production mechanisms, but also on thermalization, due to elastic collisions, reducing the width of the emission line coming from the O([SUP]1[/SUP]D) level, which has a longer lifetime. [less ▲]

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See detailCan the collapse of a fly ash heap develop into an air-fluidized flow? - Reanalysis of the Jupille accident (1961)
Stilmant, Frédéric ULg; Pirotton, Michel ULg; Archambeau, Pierre ULg et al

in Geomorphology (2015), 228

A fly ash heap collapse occurred in Jupille (Liege, Belgium) in 1961. The subsequent flow of fly ash reached a surprisingly long runout and had catastrophic consequences. Its unprecedented degree of ... [more ▼]

A fly ash heap collapse occurred in Jupille (Liege, Belgium) in 1961. The subsequent flow of fly ash reached a surprisingly long runout and had catastrophic consequences. Its unprecedented degree of fluidization attracted scientific attention. As drillings and direct observations revealed no water-saturated zone at the base of the deposits, scientists assumed an air-fluidization mechanism, which appeared consistent with the properties of the material. In this paper, the air-fluidization assumption is tested based on two-dimensional numerical simulations. The numerical model has been developed so as to focus on the most prominent processes governing the flow, with parameters constrained by their physical interpretation. Results are compared to accurate field observations and are presented for different stages in the model enhancement, so as to provide a base for a discussion of the relative influence of pore pressure dissipation and pore pressure generation. These results show that the apparently high diffusion coefficient that characterizes the dissipation of air pore pressures is in fact sufficiently low for an important degree of fluidization to be maintained during a flow of hundreds of meters. [less ▲]

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See detailDust from Comet 209P/LINEAR during its 2014 Return: Parent Body of a New Meteor Shower, the May Camelopardalids
Ishiguro, Masateru; Kuroda, Daisuke; Hanayama, Hidekazu et al

in The Astrophysical Journal Letters (2015), 798

We report a new observation of the Jupiter family comet 209P/LINEAR during its 2014 return. The comet is recognized as a dust source of a new meteor shower, the May Camelopardalids. 209P/LINEAR was ... [more ▼]

We report a new observation of the Jupiter family comet 209P/LINEAR during its 2014 return. The comet is recognized as a dust source of a new meteor shower, the May Camelopardalids. 209P/LINEAR was apparently inactive at a heliocentric distance r<SUB>h</SUB> = 1.6 AU and showed weak activity at r<SUB>h</SUB> <= 1.4 AU. We found an active region of <0.001% of the entire nuclear surface during the comet's dormant phase. An edge-on image suggests that particles up to 1 cm in size (with an uncertainty of factor 3-5) were ejected following a differential power-law size distribution with index q = –3.25 ± 0.10. We derived a mass-loss rate of 2-10 kg s<SUP>–1</SUP> during the active phase and a total mass of ≈5 × 10<SUP>7</SUP> kg during the 2014 return. The ejection terminal velocity of millimeter- to centimeter-sized particles was 1-4 m s<SUP>–1</SUP>, which is comparable to the escape velocity from the nucleus (1.4 m s<SUP>–1</SUP>). These results imply that such large meteoric particles marginally escaped from the highly dormant comet nucleus via the gas drag force only within a few months of the perihelion passage. [less ▲]

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See detailThe binary near-Earth Asteroid (175706) 1996 FG3 - An observational constraint on its orbital evolution
Scheirich, P.; Pravec, P.; Jacobson, S. A. et al

in Icarus (2015), 245

Using our photometric observations taken between April 1996 and January 2013 and other published data, we derived properties of the binary near-Earth Asteroid (175706) 1996 FG<SUB>3</SUB> including new ... [more ▼]

Using our photometric observations taken between April 1996 and January 2013 and other published data, we derived properties of the binary near-Earth Asteroid (175706) 1996 FG<SUB>3</SUB> including new measurements constraining evolution of the mutual orbit with potential consequences for the entire binary asteroid population. We also refined previously determined values of parameters of both components, making 1996 FG<SUB>3</SUB> one of the most well understood binary asteroid systems. With our 17-year long dataset, we determined the orbital vector with a substantially greater accuracy than before and we also placed constraints on a stability of the orbit. Specifically, the ecliptic longitude and latitude of the orbital pole are 266 ° and - 83 ° , respectively, with the mean radius of the uncertainty area of 4 ° , and the orbital period is 16.1508 ± 0.0002 h (all quoted uncertainties correspond to 3σ). We looked for a quadratic drift of the mean anomaly of the satellite and obtained a value of 0.04 ± 0.20 deg /yr<SUP>2</SUP> , i.e., consistent with zero. The drift is substantially lower than predicted by the pure binary YORP (BYORP) theory of McMahon and Scheeres (McMahon, J., Scheeres, D. [2010]. Icarus 209, 494-509) and it is consistent with the tigidity and quality factor of μQ = 1.3 ×10<SUP>7</SUP> Pa using the theory that assumes an elastic response of the asteroid material to the tidal forces. This very low value indicates that the primary of 1996 FG<SUB>3</SUB> is a 'rubble pile', and it also calls for a re-thinking of the tidal energy dissipation in close asteroid binary systems. [less ▲]

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See detailFood provioning influences ranging patterns in northern pigtailed macaques (Macaca leonina)
Huynen, Marie-Claude ULg; Savini, Tommaso ULg; Asensio, Norberto et al

in International Journal of Primatology (2015, January)

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See detailDocumentário e mal-entendido. Retorno sobre uma primeira filmagem no Brasil
Hamers, Jérémy ULg

in Stols, Eddy; Mascaro, Luciana; Bueno, Clodoaldo (Eds.) Brasil e Bélgica: Cinco Séculos de Conexões e Interação (2015)

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