Last 7 days
Bookmark and Share    
See detailState of Martian Upper Atmosphere as Observed by Imaging Ultraviolet Spectroscope Onboard MAVEN
Jain; Stewart; Deighan et al

Conference (2017, August 09)

NASA’s MAVEN spacecraft has taken more than two earth years (one Martian year) of observations of Mars to understand the process of Martian atmospheric evolution. The Imaging Ultraviolet Spectrograph ... [more ▼]

NASA’s MAVEN spacecraft has taken more than two earth years (one Martian year) of observations of Mars to understand the process of Martian atmospheric evolution. The Imaging Ultraviolet Spectrograph (IUVS) on board MAVEN observes Mars in far and mid ultraviolet (110-340 nm) with unique scanning and pointing capabilities, which are optimized for airglow studies. Dayglow emissions observed on Mars are a perfect tracer for the processes occurring in the emitting region of the atmosphere (100-200 km) and provide basic information about atmospheric composition (and its structure), and give insight into the dynamics, energetics, and physics and chemistry of the thermosphere. With its wide spatial and temporal coverage, IUVS observations of Martian dayglow has contributed immensely to our understanding of the Martian upper atmosphere and its response to incoming solar flux (EUV/FUV) and coupling between lower and upper atmosphere through tides and waves. In this presentation, I will talk about an overview of scientific results obtained by IUVS dayglow measurements, including (1) spatial/temporal distribution of major MUV and FUV emissions and their seasonal variability; (2) the seasonal variation of thermosphere temperatures inferred from dayglow measurements; (3) the effect of solar EUV flux (including the ~27-day solar rotation) and heliocentric distance on upper atmosphere temperature structure. We will present an overview of these results and a discussion of their implications for the state of the Martian upper atmosphere. [less ▲]

Detailed reference viewed: 15 (0 ULg)
See detailHydrogen Loss from Mars: Seasonal and Sourced from Upper Atmospheric Water
Chaffin; Deighan; Stewart et al

Conference (2017, August 09)

Mars has lost a significant fraction of its initial water inventory to space over its history. This loss proceeds via a chemical chain initiated in the lower and middle atmosphere below 100 km altitude ... [more ▼]

Mars has lost a significant fraction of its initial water inventory to space over its history. This loss proceeds via a chemical chain initiated in the lower and middle atmosphere below 100 km altitude, which results in H escape to space in the collisionless corona above about 200 km altitude. Hydrogen loss from Mars is tracked via brigtness measurements of this corona in Lyman alpha light at 121.6 nm, which is scattered by neutral H orbiting and escaping the planet. Here we present observations of H escape variability made by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission's Imaging Ultraviolet Spectrograph (IUVS) that demonstrate the seasonal dependence of H escape, adding to evidence initially gathered by Mars Express and the Hubble Space Telescope. We show that for two Mars years the atmosphere has exhibited enhanced H escape in Southern Summer near perihelion. We also present the result of photochemical model calculations which demonstrate that this variation can be explained as a result of high concentrations of water vapor in the upper atmosphere, consistent with Mars Express solar occultation measurements and several general circulation models. Our results demonstrate that the large variations in H escape at high altitudes can be driven by lower atmospheric dynamics, suggesting that Mars hydrogen escape may depend on climate, in addition to the long-term evolution of Martian climate depending on atmospheric escape. [less ▲]

Detailed reference viewed: 14 (0 ULg)
See detailScience Highlights from MAVEN/IUVS After Two Years in Mars Orbit
Jain; Schneider; Stiepen, Arnaud ULg et al

Conference (2017, August 08)

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission's Imaging Ultraviolet Spectrograph (IUVS) observes Mars in the far and mid ultraviolet (110-340 nm), investigating lower and upper atmospheric ... [more ▼]

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission's Imaging Ultraviolet Spectrograph (IUVS) observes Mars in the far and mid ultraviolet (110-340 nm), investigating lower and upper atmospheric structure and indirectly probing neutral atmospheric escape. The instrument is among the most powerful spectrographs sent to another planet, with several key capabilities: separate Far-UV & Mid-UV channels for stray light control; a high-resolution echelle mode to resolve deuterium and hydrogen emission; internal instrument pointing and scanning capabilities to allow complete mapping and nearly continuous operation; and optimization for airglow studies. After two Earth years in orbit (one Mars year), IUVS has assembled a large quantity of data and provided insights on present-day processes at Mars including dayglow, nightglow, aurora, meteor showers, clouds, and solar-planetary interactions. In this presentation, we will highlight several new discoveries made by IUVS. Among the key results obtained by IUVS are: (1) discovery of the widespread occurrence of a diffuse proton aurora representing a previously unknown source of energy deposition into the atmospheres of unmagnetized planets; (2) first spatial mapping of nitric oxide nightglow reveals regions of atmospheric downwelling necessitating substantial changes to global atmospheric circulation models; (3) a new high-spatial-resolution UV imaging mode allows detection of clouds from nadir to limb and their local time evolution, as well as unprecedented determinations of Mars’ low-altitude ozone; (4) discovery of a persistent meteoric metal layer in Martian atmosphere; (5) atmospheric structure, composition and dynamics from stellar occultation. We will present an overview of these results and a discussion of their implications for characterizing the state of the atmosphere and its evolution. [less ▲]

Detailed reference viewed: 40 (0 ULg)
See detailMAVEN/IUVS Observations of the Reflectance Spectrum of Phobos
Chaffin; Deighan; Schneider et al

Conference (2017, August 08)

The Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft occasionally has close encounter seasons with Phobos as a consequence of its orbital precession and its apoapsis being near the orbit of the ... [more ▼]

The Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft occasionally has close encounter seasons with Phobos as a consequence of its orbital precession and its apoapsis being near the orbit of the moon. During one encounter season in late 2015, MAVEN's Imaging Ultraviolet Spectrograph (IUVS) was able to gather the first ever spectral images of the moon in the mid-ultraviolet. During these flybys, IUVS was able to observe the trailing hemisphere of the moon, producing spectra useful for comparison with the Mariner 9 Ultraviolet Spectrometer measurements, which observed only the moon's leading side. The IUVS data reveal that the trailing side of the Moon is bluer than the leading side, indicating possible differences in the weathering history of the hemispheres. In addition, we see some evidence for an absorption feature longward of 300 nm, potentially produced by organic compounds, in accordance with Mariner 9 and SPICAM/UV observations. We will present an overview of our images and spectra and a discussion of their interpretation for the history and formation of Phobos. [less ▲]

Detailed reference viewed: 11 (0 ULg)
Full Text
Peer Reviewed
See detailExergy analysis applied to performance of buildings in Europe
Sartor, Kevin ULg; Dewallef, Pierre ULg

in Energy and Buildings (2017), 148

Energy performance of buildings generally assesses the energy consumption of buildings such as heating, domestic heat water, ventilation systems, etc. However, this approach is based on the first law of ... [more ▼]

Energy performance of buildings generally assesses the energy consumption of buildings such as heating, domestic heat water, ventilation systems, etc. However, this approach is based on the first law of thermodynamics and considers only the quantity of energy used without considering its ‘quality’ and leads to a lack of information about the energy conversion processes. This is particularly true in the new low-energy buildings where sometimes high temperatures sources are used to meet low-temperature needs. The exergy analysis of a system, based on first and second thermodynamic laws, can be used to overcome this. In this work, it is proposed to compare the energy and the exergy consumption and the related CO2 emissions of several kinds of buildings to determine the best systems in terms of energy and exergy needs. The energy demand calculations are performed using the official software available in Belgium and some assumptions are implemented to consider the exergy approach. As exergy calculations require a reference state, some different climatic conditions are also investigated. Finally, some conclusions are discussed to rank the sources of energy and their related exergy losses. [less ▲]

Detailed reference viewed: 21 (6 ULg)
Full Text
See detailMolecular Tools for the Detection and Quantification of Toxigenic Cyanobacteria
Kurmayer, Rainer; Sivonen, Kaarina; Wilmotte, Annick ULg et al

Book published by John Wiley and sons LTD - This edition first published 2017 (2017)

A guide to state-of-the-art molecular tools for monitoring and managing the toxigenicity of cyanobacteria Runaway climate change has made the monitoring and management of toxigenic organisms in the ... [more ▼]

A guide to state-of-the-art molecular tools for monitoring and managing the toxigenicity of cyanobacteria Runaway climate change has made the monitoring and management of toxigenic organisms in the world’s bodies of water more urgent than ever. In order to influence public policy regarding the detection and quantification of those organisms, it is incumbent upon scientists to clearly demonstrate to policy makers the increase of toxigenic cyanobacteria and the threats they pose. As molecular methods can handle many samples in short time, they are the most reliable, cost-effective tools currently available for tracking cyanotoxicity worldwide. This volume arms scientists with the tools they need to track toxigenicity in surface waters and food supplies and, hopefully, to develop new techniques for managing the spread of toxic cyanobacteria. This book offers the first comprehensive treatment of molecular tools for monitoring cyanotoxicity. Growing out of the findings of the landmark European Cooperation in Science and Technology Cyanobacteria project (CYANOCOST), it provides detailed, practical coverage of the full array of available molecular tools and protocols, from water sampling, nucleic acid extraction, and downstream analysis—including PCR and qPCR based methods—to genotyping (DGGE), diagnostic microarrays, and community characterization using next-gen sequencing techniques. [less ▲]

Detailed reference viewed: 151 (2 ULg)
Full Text
See detailBioinformatic Processing of Amplicon Sequencing Datasets
Sweetlove, Maxime; Obbels, Dagmar; Verleyen, Elie et al

in Kurmayer, Rainer; Sivonen, Kaarina; Wilmotte, Annick (Eds.) et al Molecular Tools for the Detection and Quantification of Toxigenic Cyanobacteria (2017)

Amplicon sequencing can be a very powerful approach for detecting toxic cyanobacteria or any other kind of microorganism during monitoring programs. However, owing to the huge size of next-generation ... [more ▼]

Amplicon sequencing can be a very powerful approach for detecting toxic cyanobacteria or any other kind of microorganism during monitoring programs. However, owing to the huge size of next-generation sequencing (NGS) datasets (up to several Gb), there is an obvious need for semi-automatic data processing and statistical analysis, as well as visualization of the patterns found. Importantly, raw NGS data contain errors, some of which are easily detected (e.g. too short or low-quality reads), while others remain hidden even after the most stringent quality controls (e.g. chimeras, contaminations, reads with large insertions or deletions, referred to as “indels”). As a consequence, NGS data need to be interpreted with caution, and bioinformatics analysis implementing poor error identification can easily lead to erroneous conclusions. Hence, a crucial step in the analysis of NGS data is the detection and removal of as many erroneous reads as possible. Moreover, bioinformatics involve additional preprocessing steps, including demultiplexing (i.e. grouping reads to samples according to the barcode sequence), deleting non-biological tags together with the adaptors and primer sequences, and removing chimeric sequences. In addition, the bioinformatics pipelines enable the quality-filtered sequences to be clustered into biologically relevant operational taxonomic units (OTUs), which form the basis of the statistical analysis, including the calculation of alpha- and beta-diversity. [less ▲]

Detailed reference viewed: 19 (2 ULg)
Full Text
See detailTaxonomic Identification of Cyanobacteria by a Polyphasic Approach
Wilmotte, Annick ULg; Laughinghouse, Dail Haywood IV; Capelli, Camilla et al

in Kurmayer, Rainer; Sivonen, Kaarina; Wilmotte, Annick (Eds.) et al Molecular Tools for the Detection and Quantification of Toxigenic Cyanobacteria (2017)

In this chapter, we shall discuss the criteria and methods to be adopted for the taxonomic identification and classification of cyanobacteria. This includes a brief introduction of the two Codes of ... [more ▼]

In this chapter, we shall discuss the criteria and methods to be adopted for the taxonomic identification and classification of cyanobacteria. This includes a brief introduction of the two Codes of Nomenclature ruling in parallel on the valid naming of these organisms. We shall then present the major steps important for cyanobacterial taxa identification and their nomenclature. These include: 1) determination of morphology by light microscopy; 2) genetic characterization by single and/or multilocus sequence typing; 3) the assignment of the organism to a taxonomic entity (genus, species, eco- and/or genotype within a species) by reference to, and phylogenetic analysis of, cyanobacterial nucleotide sequences available in public repositories. Ideally, these methods should be accompanied by the determination of other relevant properties (ultrastructural, physiological, biochemical, and ecological characteristics) that may help to define/redefine and circumscribe the cyanobacterial taxon under study. [less ▲]

Detailed reference viewed: 37 (1 ULg)
Full Text
See detailIsolation, Purification, and Cultivation of Toxigenic Cyanobacteria
Haande, Sigrid; Jasser, Iwona; Gugger, Muriel et al

in Kurmayer, Rainer; Sivonen, Kaarina; Wilmotte, Annick (Eds.) et al Molecular Tools for the Detection and Quantification of Toxigenic Cyanobacteria (2017)

This chapter summarizes the most commonly used methods for the isolation, purification, and cultivation of toxic cyanobacteria. The aim is to give general advice on how to isolate and maintain clonal ... [more ▼]

This chapter summarizes the most commonly used methods for the isolation, purification, and cultivation of toxic cyanobacteria. The aim is to give general advice on how to isolate and maintain clonal cyanobacterial cultures in order to use them in genetic studies. The traditional methods for the isolation of cyanobacteria into culture are well established and described and there are several excellent reviews with detailed information on culturing techniques [less ▲]

Detailed reference viewed: 25 (1 ULg)
Full Text
See detailDNA (Diagnostic) and cDNA Microarray
Rantala-Yilinen, Anne; Sivonen, Kaarina; Wilmotte, Annick ULg

in Kurmayer, Rainer; Sivonen, Kaarina; Wilmotte, Annick (Eds.) et al Molecular Tools for the Detection and Quantification of Toxigenic Cyanobacteria (2017)

Diagnostic microarrays have been used to study cyanobacterial diversity in environmental samples. They usually include sequences (probes) for only one or a few genes allowing a number of genera/species to ... [more ▼]

Diagnostic microarrays have been used to study cyanobacterial diversity in environmental samples. They usually include sequences (probes) for only one or a few genes allowing a number of genera/species to be detected. In contrast, cDNA microarrays are used for screening genome-wide changes in gene expression and include probes for all or most genes in one strain . The purpose of this sub-chapter is to introduce the principle of a diagnostic microarray (= DNA chip) that uses a ligation detection reaction (LDR) and universal microarray to simultaneously detect and identify all potential microcystin and nodularin producers present in a sample. This is especially useful when monitoring environmental samples that can contain many cyanobacterial genera, including toxin-producing strains. [less ▲]

Detailed reference viewed: 12 (1 ULg)
Full Text
Peer Reviewed
See detailAssessing quality of life using structural equation modeling
Dardenne, Nadia ULg; Pétré, Benoît ULg; Husson, Eddy ULg et al

Poster (2017, August)

Detailed reference viewed: 36 (3 ULg)
Full Text
Peer Reviewed
See detailSimilarity of the Jovian satellite footprints: spots multiplicity and dynamics
Bonfond, Bertrand ULg; Grodent, Denis ULg; Badman, S. V. et al

in Icarus (2017), 292(2017), 208217

In the magnetospheres of Jupiter and Saturn, the intense interaction of the satellites Io, Europa, Ganymede and Enceladus with their surrounding plasma environment leaves a signature in the aurora of the ... [more ▼]

In the magnetospheres of Jupiter and Saturn, the intense interaction of the satellites Io, Europa, Ganymede and Enceladus with their surrounding plasma environment leaves a signature in the aurora of the planet. Called satellite footprints, these auroral features appear either as a single spot (Europa and Enceladus) or as multiple spots (Io and Ganymede). Moreover, they can be followed by extended trailing tails in the case of Io and Europa, while no tail has been reported for Ganymede and Enceladus, yet. Here we show that all Jovian footprints can be made of several spots. Furthermore, the footprints all experience brightness variations on timescale of 2-3 minutes. We also demonstrate that the satellite location relative to the plasma sheet is not the only driver for the footprint brightness, but that the plasma environment and the magnetic field strength also play a role. These new findings demonstrate that the Europa and Ganymede footprints are very similar to the Io footprint. As a consequence, the processes expected to take place at Io, such as the bi-directional electron acceleration by Alfvén waves or the partial reflection of these waves on plasma density gradients, can most likely be extended to the other footprints, suggesting that they are indeed universal processes. [less ▲]

Detailed reference viewed: 69 (14 ULg)
Full Text
Peer Reviewed
See detailInfluence of urban patterns on flooding
Bruwier, Martin ULg; Mustafa, Ahmed; Aliaga, Daniel et al

in E-proceedings of the 37th IAHR World Congress (2017, August)

The goal of this paper is to identify the respective influence of different characteristics of urban patterns on urban flooding. A set of 2,290 alternate urban patterns was generated randomly using an ... [more ▼]

The goal of this paper is to identify the respective influence of different characteristics of urban patterns on urban flooding. A set of 2,290 alternate urban patterns was generated randomly using an urban generator tool providing the geometry of buildings and their relative location to the ground, over a square area of 1 km². Steady 2-D hydraulic computations were performed for these 2,290 different urban patterns with identical hydraulic boundary conditions. The computational time was reduced by using an anisotropic porosity model. This model uses relatively coarse computational cells; but preserves information from the detailed topographic data through the use of porosity parameters. Based on the computed maps of waterdepths for the 2,290 urban patterns, a sensitivity analysis based on a multiple linear regression was performed to outline the most influential urban characteristics. [less ▲]

Detailed reference viewed: 103 (28 ULg)
Peer Reviewed
See detailVoice use among music theory teachers
Schiller, Isabel ULg; Morsomme, Dominique ULg; Sfez, Lou et al

Conference (2017, August)

In Belgium, there is a particular group of music teachers referred to as music theory teachers. Working at music schools, they convey theoretical knowledge and practical musical skills to groups of ... [more ▼]

In Belgium, there is a particular group of music teachers referred to as music theory teachers. Working at music schools, they convey theoretical knowledge and practical musical skills to groups of individuals who learn music during their free-time. Even though music theory teachers use both speaking and singing voice intensively at work, little is known about their voice use profiles. This study investigated the vocal loading among French-speaking music theory teachers. Objectives were (1) to describe their professional and extra-professional vocal loading, (2) to determine the relationship between vocal loading and background noise level and (3) to investigate whether objectively measured vocal loading is reflected in music theory teachers’ auto-evaluation of their voice. Using voice dosimetry, 13 music theory teachers were monitored for one workweek. Parameters analysed were F0, voice sound pressure level (SPL), phonation time, vocal loading index (VLI) and background noise SPL. At the end of each monitoring day, subjects self-assessed their voice use by means of visual analogue scales. Results revealed (1) significantly higher vocal loading in the professional context than in the extra-professional context, (2) significant positive correlations between background noise level and the parameters F0, voice SPL and phonation time and (3) significant correlations between the VLI and auto-evaluation data (e.g. voice quality and vocal fatigue). These results highlight that teaching music theory is a profession with high vocal demands. At work, music theory teachers are exposed to high background noise, which seems to influence their voice use and may potentially contribute to the development of voice problems among this population. Visual analogue scales provide a promising tool to subjectively investigate vocal loading among music theory teachers. [less ▲]

Detailed reference viewed: 23 (4 ULg)
Full Text
Peer Reviewed
See detailEarly eukaryotes: insights from microanalyses of proterozoic microfossils
Cornet, Yohan ULg; Beghin, Jérémie ULg; Kabamba Baludikay, Blaise ULg et al

in Goldschmidt Abstracts, 2017 (2017, August)

Detailed reference viewed: 13 (1 ULg)
Full Text
Peer Reviewed
See detailAn efficient algorithm to decide periodicity of b-recognisable sets using MSDF convention
Boigelot, Bernard ULg; Mainz, Isabelle ULg; Marsault, Victor ULg et al

in Leibniz International Proceedings in Informatics (2017, August), 80

Given an integer base b>1, a set of integers is represented in base b by a language over {0,1,...,b-1}. The set is said to be b-recognisable if its representation is a regular language. It is known that ... [more ▼]

Given an integer base b>1, a set of integers is represented in base b by a language over {0,1,...,b-1}. The set is said to be b-recognisable if its representation is a regular language. It is known that eventually periodic sets are b-recognisable in every base b, and Cobham's theorem implies the converse: no other set is b-recognisable in every base b. We are interested in deciding whether a $b$-recognisable set of integers (given as a finite automaton) is eventually periodic. Honkala showed that this problem is decidable in 1986 and recent developments give efficient decision algorithms. However, they only work when the integers are written with the least significant digit first. In this work, we consider the natural order of digits (Most Significant Digit First) and give a quasi-linear algorithm to solve the problem in this case. [less ▲]

Detailed reference viewed: 8 (2 ULg)
Full Text
See detailAs teorias semióticas face à fotografia
Dondero, Maria Giulia ULg

in Calavari, Suzi; Rodrigues, Angelica; Rocha, Nildicéia (Eds.) Proceedings VI SELIN – NOVAS PRÁTICAS EM PESQUISA SOBRE A LINGUAGEM: ROMPENDO FRONTEIRAS (2017, August)

Dans ce texte, je me propose de revenir sur les travaux en sémiotique qui ont marqué les études du champ interdisciplinaire de la photographie et de les poursuivre; l’objectif principal est de fournir ... [more ▼]

Dans ce texte, je me propose de revenir sur les travaux en sémiotique qui ont marqué les études du champ interdisciplinaire de la photographie et de les poursuivre; l’objectif principal est de fournir quelques pistes pour étudier, d’un point de vue sémiotique, l’image photographique en tant qu’objet pris dans des pratiques d’usage et d’interprétation diversifiées au sein des statuts sociaux de l’art, de la science, de la religion. [less ▲]

Detailed reference viewed: 22 (2 ULg)