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See detailDirect detection of Aspergillus and azole resistance of Aspergillus fumigatus on broncho-alveolar lavage fluid. Validation of a new Aspergillus real-time PCR
Chong, Ga-Lai; Van de Sande, Wendy; Dingemans, Gijs et al

in Journal of Clinical Microbiology (2015)

Introduction Azole resistance in Aspergillus fumigatus is increasingly reported. We describe the validation of AsperGenius® , a new multiplex real-time polymerase chain reaction (PCR) assay consisting of ... [more ▼]

Introduction Azole resistance in Aspergillus fumigatus is increasingly reported. We describe the validation of AsperGenius® , a new multiplex real-time polymerase chain reaction (PCR) assay consisting of two multiplex real-time PCRs: one which identifies the clinically relevant Aspergillus species, and one which detects the TR34, L98H, T289A, Y121F mutations in CYP51A and differentiates susceptible from resistant A. fumigatus strains. Methods The diagnostic performance was tested on 37 bronchoalveolar lavage (BAL) samples from haematology patients and on 40 BAL samples from intensive care unit (ICU) patients using BAL galactomannan ≥1.0 or positive culture as the gold standard for the presence of Aspergillus. Results In the haematology and ICU groups combined, there were 22 BAL samples with IA (2 proven, 9 probable and 11 non-classifiable). Nineteen of the 22 BAL samples were positive according to the gold standard. The optimal cycle threshold value for the presence of Aspergillus was <36. Sixteen of the 19 BAL samples had a positive PCR (2 Aspergillus species and 14 A. fumigatus). This resulted in a sensitivity, specificity, positive and negative predictive value of 88.9%, 89.3%, 72.7% and 96.2% for the haematology group and 80.0%, 93.3%, 80.0% and 93.3% in the ICU group, respectively. The CYP51A real-time PCR confirmed 12 wildtype and 2 resistant strains (1 TR34/L98H and 1 TR46/Y121F/T289A mutant). Conclusion The AsperGenius® multiplex real-time PCR allows for a sensitive and fast detection of Aspergillus species directly in BAL samples. More importantly, this assay detects and differentiates wildtype from resistant strains even if BAL cultures remained negative. [less ▲]

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See detailAbsence of Varicella Zoster Virus Reactivation after Infliximab Administration for Plaque Psoriasis
EL HAYDERI, Lara ULg; BONTEMS, Sébastien ULg; MEEX, Cécile ULg et al

in Dermatology (2015)

Background: Herpes zoster (HZ) in patients receiving tumor necrosis factor (TNF) antagonists may be more severe and the incidence seems increased. The influence of TNF antagonists on varicella zoster ... [more ▼]

Background: Herpes zoster (HZ) in patients receiving tumor necrosis factor (TNF) antagonists may be more severe and the incidence seems increased. The influence of TNF antagonists on varicella zoster virus (VZV) reactivation is unknown. Objective: To prospectively search in a pilot study for VZV DNA in sequential blood samples before and after infliximab administration. Setting: University medical center. Subjects and Methods: Blood samples of six patients with longstanding and severe plaque psoriasis were taken on day 1 (before infliximab administration) and on days 2, 7, 21 and 42 for the determination of VZV viremia by ORF21 real-time polymerase chain reaction. Patients with varicella, HZ and normal subjects were included as controls. Results: None of the six patients presented VZV viremia at any of the time points. Highload viremia was present during varicella, low-load viremia in some HZ patients and no viremia in the control patients. Limitations: Small number of patients. Conclusions: In this pilot study, infliximab did not reactivate VZV and did not induce subclinical VZV viremia. [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 detailStable climate and surface mass balance in Svalbard over 1979–2013 despite the Arctic warming
Lang, Charlotte ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg

in Cryosphere (The) (2015), 9

With the help of the regional climate model MAR (Modèle Atmosphérique Régional) forced by the ERA-Interim reanalysis (MARERA) and the MIROC5 (Model for Interdisciplinary Research on Climate) global model ... [more ▼]

With the help of the regional climate model MAR (Modèle Atmosphérique Régional) forced by the ERA-Interim reanalysis (MARERA) and the MIROC5 (Model for Interdisciplinary Research on Climate) global model (MARMIROC5) from the CMIP5 (Coupled Model Intercomparison Project) database, we have modelled the climate and surface mass balance of Svalbard at a 10 km resolution over 1979–2013. The integrated total surface mass balance (SMB) over Svalbard modelled by MARERA is negative (−1.6 Gt yr−1) with a large interannual variability (7.1 Gt) but, unlike over Greenland, there has been no acceleration of the surface melt over the past 35 years because of the recent change in atmospheric circulation bringing northwesterly flows in summer over Svalbard, contrasting the recent observed Arctic warming. However, in 2013, the atmospheric circulation changed to a south–southwesterly flow over Svalbard causing record melt, SMB (−20.4 Gt yr−1) and summer temperature. MIROC5 is significantly colder than ERA-Interim over 1980–2005 but MARMIROC5 is able to improve the near-surface MIROC5 results by simulating not significant SMB differences with MARERA over 1980–2005. On the other hand, MIROC5 does not represent the recent atmospheric circulation shift in summer and induces in MARMIROC5 a significant trend of decreasing SMB (−0.6 Gt yr−2) over 1980–2005. [less ▲]

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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 detailClostridium difficile from food and surface samples in a Belgian nursing home: An unlikely source of contamination
Rodriguez Diaz, Cristina ULg; Korsak Koulagenko, Nicolas ULg; Taminiau, Bernard ULg et al

in Anaerobe (2015), 32

This study investigates the contamination of foods and surfaces with Clostridium difficile in a single nursing home. C. difficile PCR-ribotype 078 was found in one food sample and in none of the tested ... [more ▼]

This study investigates the contamination of foods and surfaces with Clostridium difficile in a single nursing home. C. difficile PCR-ribotype 078 was found in one food sample and in none of the tested surfaces. These results indicate that food and surfaces are an unlikely source of C. difficile infection in this setting. [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 detailSeasonal variability of meiofauna, especially harpacticoid copepods, in Posidonia oceanica macrophytodetritus accumulations
Mascart, Thibaud ULg; Lepoint, Gilles ULg; Deschoemaeker, Silke et al

in Journal of Sea Research (2015), 95

The overall aim of this study was (1) to assess the diversity and density of meiofauna taxa, especially harpacticoid copepod species, present within accumulated seagrass macrophytodetritus on unvegetated ... [more ▼]

The overall aim of this study was (1) to assess the diversity and density of meiofauna taxa, especially harpacticoid copepod species, present within accumulated seagrass macrophytodetritus on unvegetated sand patches and (2) to elucidate the community structure of detritus-associated harpacticoid copepods in relation to natural temporal variability of physico-chemical characteristics of accumulations. This was investigated in a Posidonia oceanica (L.) Delile seagrass ecosystem in the northwest Mediterranean Sea (Bay of Calvi, Corsica, 42°35’N, 8°43’E) using a triplicate macrophytodetritus core field sampling in two contrasting sites over the four seasons of 2011. Meiofauna higher taxa consisted of 50% Copepoda, which 87% belonged to the Harpacticoida order. Nematoda was the second most abundant taxa. The copepod community displayed a wide variety of morphologically similar and ecologically different species (i.e. mesopsammic, phytal, phytal-swimmers, planktonic and parasitic). The harpacticoid copepod community followed a strong seasonal pattern with highest abundances and species diversity in May-August, revealing a link with the leaf litter epiphyte primary production cycle. Aside from the important role in sheltering, housing and feeding potential of macrophytodetritus, a harpacticoid community BEST analysis demonstrated a positive correlation with habitat complexity and a negative correlation with water movements and P. oceanica leaf litter accumulation. [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 detailAn X-ray surprise in a magnetic pulsator
Nazé, Yaël ULg

in IAU Symposium (2015, January 01)

ξ[SUP]1[/SUP] CMa is a rare β Cep star with a strong magnetic field. To gain new insight on this object, a dedicated campaign using XMM-Newton was performed. These data reveal a new type of variations, X ... [more ▼]

ξ[SUP]1[/SUP] CMa is a rare β Cep star with a strong magnetic field. To gain new insight on this object, a dedicated campaign using XMM-Newton was performed. These data reveal a new type of variations, X-ray pulsations, posing a new challenge to our understanding of stellar winds. [less ▲]

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