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See detailGPS, Galileo and BeiDou inter-system biases estimation in relative positioning with code and phase pseudoranges
Deprez, Cécile ULg; Warnant, René ULg

Conference (2016, September 07)

The recent increase in the number of Global Navigation Satellite Systems (GNSS) opens new perspectives in the field of high precision positioning. Particularly, the Chinese BeiDou satellite system and the ... [more ▼]

The recent increase in the number of Global Navigation Satellite Systems (GNSS) opens new perspectives in the field of high precision positioning. Particularly, the Chinese BeiDou satellite system and the European Galileo program have experienced major progress in 2015 and 2016 with the launch of 7 and 8 satellites respectively. Associated with the ongoing GPS modernization, many more frequencies and satellites are now available. Therefore, multi-GNSS relative positioning based on overlapping frequencies should entail better accuracy and reliability in position estimations. However, the differences between satellite systems induce inter-system biases (ISBs) inside the multi-GNSS equations of observation. The combined use of L1 and L5 from GPS with E1 and E5a from Galileo, B2 from BeiDou and E5b from Galileo in zero baseline double differences (ZB DD) based on a unique pivot satellite is employed to resolve ISBs. This model removes all the satellite- and receiver-dependent error sources by differentiating and the zero baseline configuration allows atmospheric and multipath effects elimination. An analysis of the long-term stability of ISBs (GPS- Galileo and Galileo - BeiDou) is conducted onvariouspairsof receiversover large timespans. Thepossibleinfluenceof temperature variations inside the receivers over ISB values is also investigated. Our study is based on the 6 multi-GNSS receivers (2 Septentrio PolaRx4, 1 Septentrio PolaRxS, 1 Septentrio PolaRx5 and 2 Trimble NetR9) installed on the roof of our building in Liege. The estimated ISBs are then used as corrections in the multi-GNSS observation model and the resulting accuracy of multi-GNSS positioning is compared to GPS, Galileo and BeiDou standalone solutions. [less ▲]

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See detailContribution to the study of the mineral hypothesis in relation to the Kashin-Beck disease in Tibet Autonomous Region
DERMIENCE, Michael ULg

Doctoral thesis (2016)

A little known disease called Kashin-Beck disease (KBD) plagues the poor and rural populations in the Tibet Autonomous Region (T.A.R.) and in other provinces of the People’s Republic of China. It is an ... [more ▼]

A little known disease called Kashin-Beck disease (KBD) plagues the poor and rural populations in the Tibet Autonomous Region (T.A.R.) and in other provinces of the People’s Republic of China. It is an endemic and chronic osteochondropathy affecting long bones and joints, sometimes as soon as of the early childhood. Although the etiology of this disease is not clearly established, little doubt remains as to the implication of multiple environmental factors. Intoxication by mycotoxins in cereals and by organic acids in water, deficiencies in selenium and iodine, are all factors having a place in the multifactorial etiology hypothesized. In T.A.R., diet, notably, differentiates the rural community, affected by KBD, from the other communities (nomads and city-dwellers), who remain unaffected. Because more than one chemical element is essential to a healthy bone metabolism, and because there is scarce data, if not any, on the topic, this thesis had to primary objective to investigate the mineral and trace element dietary status of young Tibetan children living in areas endemic for KBD. The first logical action step led us to determine which elements are involved in bone and joints metabolism through an exhaustive review of the scientific literature. Thirty elements were highlighted, and a dozen was deemed relevant in this context. An exploratory study on the Tibetan food composition concluded on a high risk of introducing important bias by using the existing food composition tables for nutritional assessment in T.A.R. Being inescapable tools, a specific food composition table was elaborated for our area of investigation with the close collaboration of the China National Center for Food Safety Risk Assessment (CFSA). During a scientific internship of 7 month in the CFSA, 19 chemical elements were analyzed in not less than 1119 samples of sixteen traditional foods and beverages of rural T.A.R. In order to assess the nutritional status of the children, a cross-sectional study was implemented. 250 preschool children aged 3 to 5 years old from three rural counties around Lhasa were enrolled. They were interviewed twice, at six month of interval, via the 24-hour recall method. The results suggest several imbalances in their dietary mineral intakes compared to the Chinese recommendations. Sodium and manganese intakes are too high, while they are too low for potassium, calcium, zinc, copper and selenium. The Tibetan diet is rich in fiber and in phytic acid, which are susceptible to decrease the bioavailability and to aggravate the deficiencies of the later elements. For this reason, we conducted an animal experimentation on a rat model to assess the apparent digestibility, the fecal excretion and the urinary excretion of minerals and trace elements in the traditional Tibetan dish called tsampa pag. This traditional dish consisting of roasted barley flour mixed with yak butter tea is the mainstay of the Tibetan diet. The results of this experiment suggest low bone mineral density, a possible secondary copper deficiency, and a possible manganese excess in rats that consumed tsampa pag. In view of the results presented, it would be interesting to compare the mineral intake between children living in endemic areas and in non-endemic areas. It would also be interesting to include more of elements known to affect bone metabolism in future studies. [less ▲]

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See detailProbabilistic Measures of Earthquake Effects on Fire Performance of Tall Buildings
Elhami Khorasani, Negar; Gernay, Thomas ULg; Garlock, Maria

in Zingoni (Ed.) Proceedings of the Sixth International Conference on Structural Engineering, Mechanics and Computation (2016, September 06)

Cascading multi-hazard events, such as fires following an earthquake, can trigger progressive collapse of structures. Risk or the probability of reaching a limit state after an extreme event is related to ... [more ▼]

Cascading multi-hazard events, such as fires following an earthquake, can trigger progressive collapse of structures. Risk or the probability of reaching a limit state after an extreme event is related to (a) the probability of occurrence of the hazard, and (b) the probability of reaching the limit state given the hazard. In this paper, earthquake effects on fire performance of tall buildings in a community are studied. First, the proba-bility of fire ignition due to an earthquake is modeled based on historical data and properties of the built en-vironment. In the second step, the effect of earthquake on structural fire performance of a steel frame is studied using system level probabilistic approaches. The results show that the earthquake does not increase the probability of reaching different limit states under fire, however, post earthquake fire can increase the drift demand on columns located on the perimeter of the structure, and may cause instability. [less ▲]

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See detailUltra-narrow superconducting junctions: electromigration to shed light on quantum point contacts
Baumans, Xavier ULg; Cerbu, Dorin; Adami, Obaïd-Allah ULg et al

Conference (2016, September 06)

Superconducting nanowires have been, for years now, a topic of great interest due to their potential application in single photon detectors and in quantum computing circuits. In this context, it is of ... [more ▼]

Superconducting nanowires have been, for years now, a topic of great interest due to their potential application in single photon detectors and in quantum computing circuits. In this context, it is of fundamental importance to better understand the undesired and harmful appearance of thermal and quantum fluctuations of the superconducting order parameter [1]-[3] as a function of the wire width. Although superconductors in the mesoscopic regime (i.e. size comparable to ξ and/or λ) have been explored both experimentally and theoretically in depth, the superconducting nanoworld (i.e. at scales of the fermi wavelength) has received much less attention. The lack of experimental results is in part due to the difficulty of sample fabrication, at dimensions beyond the limit reached by conventional lithographic techniques. A promising direction consists of controlling the local displacement of atom by an electron wind, a process known as electromigration (EM) [4] . This effect relies on the combination of local temperature rise and substantial current crowding at nanoconstrictions. While uncontrolled, EM is responsible for the breakdown of small electronic devices, it can be used in a controllable way to further decrease locally the cross section of the nanowire towards single atomic contacts. In this work, we explore in-situ controlled EM to fabricate nano-constrictions immersed in cryogenic environment. We demonstrate that a transition from thermally assisted phase slips (TAPS) to quantum phase slips (QPS) takes place when the effective cross section becomes smaller than ~ 150 nm 2 . In the regime dominated by QPS the nanowire loses completely its capacity to carry current without dissipation, even at the lowest possible temperature [5] . We also demonstrate that the bow-tie shaped constrictions exhibit a negative magnetoresistance at low magnetic fields [5] which can be attributed to the suppression of superconductivity in the contact leads [6] . Strikingly, the detrimental effect caused by the repeated EM can be healed by simply inverting the current direction. These findings reveal the strong potential of the proposed fabrication method to explore various fascinating superconducting phenomena in atomic-size constrictions. [less ▲]

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See detailUnusually high sea ice cover influences resource use by benthic invertebrates in coastal Antarctica
Michel, Loïc ULg; Dubois, Philippe; Eleaume, Marc et al

Poster (2016, September 05)

Antarctica currently undergoes strong and contrasted impacts linked with climate change. While the West Antarctic Peninsula is one of the most rapidly warming regions in the world, resulting in sea ice ... [more ▼]

Antarctica currently undergoes strong and contrasted impacts linked with climate change. While the West Antarctic Peninsula is one of the most rapidly warming regions in the world, resulting in sea ice cover decrease, the sea ice cover of East Antarctica unexpectedly tends to increase, possibly in relation with changes in atmospheric circulation. Changes in sea ice cover are likely to influence benthic food web structure through modifications of benthic-pelagic coupling, disruption of benthic production and/or modifications of benthic community structure (i.e. resource availability for benthic consumers). Here, we studied shallow (0-20 m) benthic food web structure on the coasts of Petrels Island (Adélie Land, East Antarctica) during an event of unusually high spatial and temporal (two successive austral summers without seasonal break-up) sea ice cover. Using stable isotope ratios of C and N and the SIAR mixing model, we examined importance of 4 organic matter sources (benthic macroalgae, benthic biofilm, sympagic algae, suspended particulate organic matter) for nutrition of dominant primary consumers and omnivores. 14 invertebrate taxa including sessile and mobile polychaetes, gastropods, bivalves, sea stars, sea urchins and sea cucumbers were studied. Our results indicate that most benthic invertebrates predominantly relied on sympagic algae. Despite its very high abundance, trophic role of benthic biofilm seemed limited. However, interpretation of data was complicated by the peculiar ecophysiological features of Antarctic invertebrates, whose very low metabolic rates could be associated to low isotopic turnover and long time to reach isotopic equilibrium with their food items. Resource use by consumers from Adélie Land markedly differed from literature data about invertebrate diet in coastal Antarctica, suggesting 1) important influence of increased sea ice cover on benthic food web structure and 2) high spatial and/or temporal variation in the feeding habits of studied organisms, likely linked with a high degree of trophic plasticity. Our results provide insights about how Antarctic benthic consumers, which have evolved in an extremely stable environment, might adapt their feeding habits in response to sudden man-driven changes in environmental conditions and trophic resource availability. [less ▲]

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See detailInternet Platforms for Education on Sustainability
Pfennig, Andreas ULg

Conference (2016, September 05)

One challenge in teaching sustainability results from the expertise being distributed in various universities. At the same time society would not require so many experts focused on sustainability that ... [more ▼]

One challenge in teaching sustainability results from the expertise being distributed in various universities. At the same time society would not require so many experts focused on sustainability that corresponding purely sustainability-oriented curricula should be offered in a majority of universities. Thus sustainability aspects have to be integrated into existing curricula e.g. in chemical engineering studies. To offer sufficiently high-level courses or teaching content, one way is to share modules dealing with sustainability aspects. The idea to share teaching capabilities on a national or international level is not new, some examples are sustainicum.at, bioenergytrain.eu. While these approaches address the topic of sustainability with a relatively wide variety of facets, it is difficult to see, how a coherent picture can be obtained and transferred in education to students and the interested public. While this is so, already regarding the most basic element of the versatile toolbox of chemical engineering, namely setting up and solving simple balances, leads to significant insights and especially a fundamental understanding on the basic interplay of at least some of the major drivers. These are – besides increasing world population, which is the main driver – the increasing energy consumption, the limited land area for food and bioenergy production, the finite size even of the atmosphere leading to an increase in CO2 concentration and climate change, to name just a few. All of these aspects refer to limited resources for which balances can be set up and solved. The balances have the advantage that they are so simple that everybody can assess their validity and implications. The experience with working out a corresponding teaching module will be presented exemplarily. To facilitate delivering the aspects to students and the interested public the teaching material including a full manuscript and power-point slides have been worked out and are supplied at sustainicum.at. To allow easy access to the content of this teaching material also corresponding lectures have been recorded and are made publicly available through YouTube. The technical boundary conditions, which were found to be quite optimal as compared to other public lectures available on the internet, will be presented. The teaching material has in the past also been used for a variety of own presentations with the aim to deliver the basic understanding to an interested public, including public conference series or school classes. From these various experiences conclusions are drawn which will be presented. Introduction: One challenge in teaching sustainability results from the expertise being distributed in various universities. At the same time society would not require so many experts focused on sustainability that corresponding purely sustainability-oriented curricula should be offered in a majority of universities. Thus sustainability aspects have to be integrated into existing curricula e.g. in chemical engineering studies. To offer sufficiently high-level courses or teaching content, one way is to share modules dealing with sustainability aspects. The idea to share teaching capabilities on a national or international level is not new, some examples are sustainicum.at, bioenergytrain.eu. While these approaches address the topic of sustainability with a relatively wide variety of facets, it is difficult to see, how a coherent picture can be obtained and transferred in education to students and the interested public. Exemplary Topic: While this is so, already regarding the most basic element of the versatile toolbox of chemical engineering, namely setting up and solving simple balances, leads to significant insights and especially a fundamental understanding on the basic interplay of at least some of the major drivers. These are – besides increasing world population, which is the main driver – the increasing energy consumption, the limited land area for food and bioenergy production, the finite size even of the atmosphere leading to an increase in CO2 concentration and climate change, to name just a few. All of these aspects refer to limited resources for which balances can be set up and solved. The balances have the advantage that they are so simple that everybody can assess their validity and implications. The experience with working out a corresponding teaching module will be presented exemplarily. Results and Conclusions: To facilitate delivering the aspects to students and the interested public the teaching material including a full manuscript and power-point slides have been worked out and are supplied at sustainicum.at. To allow easy access to the content of this teaching material also corresponding lectures have been recorded and are made publicly available through YouTube. The technical boundary conditions, which were found to be quite optimal as compared to other public lectures available on the internet, will be presented. The teaching material has in the past also been used for a variety of own presentations with the aim to deliver the basic understanding to an interested public, including public conference series or school classes. From these various experiences conclusions are drawn which will be presented. [less ▲]

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See detailInstability and abrupt changes in marine ice sheet behaviour
Bulthuis, Kevin ULg; Arnst, Maarten ULg; Pattyn, Frank et al

Conference (2016, September 05)

The West Antarctic ice sheet (WAIS), whose bedrock is to a large extent below sea level, has been identified as a tipping element in Earth’s climate system because it could dramatically re- treat and ... [more ▼]

The West Antarctic ice sheet (WAIS), whose bedrock is to a large extent below sea level, has been identified as a tipping element in Earth’s climate system because it could dramatically re- treat and cause important sea-level rise. Different mechanisms underlying instabilities of such marine ice sheets have been proposed in the literature, but the risk that these mechanisms could trigger an accelerated retreat of the WAIS is still an open question. In this oral communication, which results from the literature study that I carried out during this ongoing first year of my PhD, I will review two main mechanisms that can cause marine ice sheet instability. The first mechanism is the marine ice sheet instability explained by Weertman who hypothe- sizes that marine ice sheets grounded on bedrocks which deepen inland can be inherently unstable. I will focus my attention on the stability of the steady states of this nonlinear dyna- mical system, as well as on the critical values of the external forcing parameters responsible for abrupt changes in the system behaviour (critical transitions). I will review how geological data suggest that rapid ice sheet retreats explained by Weertman’s hypothesis occurred in Antarctica during the Pleistocene and the early Holocene. The recently observed accelerated ice loss of the Pine Island and Thwaites glaciers of the WAIS could also be considered as a consequence of this instability mechanism and could lead to an important contribution to sea-level rise in the future. The second mechanism that I will review is the binge-purge oscillation mechanism which could have caused the disintegration of the Laurentide ice sheet during the last glacial period. These oscillations could also explain future behaviour of the WAIS. Binge-purge oscillations are short periods of enhanced ice flow (purge phase) followed by periods of much slower flow (binge phase). These oscillations are usually explained by a thermal-gravitational instability which takes place when basal conditions change. I will focus my attention on the mathematical and physical conditions which can trigger this instability process, as well as on examples of such oscillations in the WAIS in the past. [less ▲]

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See detailCo-producing evidence: Ethnographic inquiry of a "wild" search for causation
Duysens, Fanny ULg

Conference (2016, September 03)

Drawing on a multi-sited ethnography which explores the field of patients’ organizations (POs) concerned with genetic disorders within the Belgian context, this communication is interested in some ... [more ▼]

Drawing on a multi-sited ethnography which explores the field of patients’ organizations (POs) concerned with genetic disorders within the Belgian context, this communication is interested in some knowledge-related collaboration between POs and scientific and medical experts, or “wild research” projects (Callon & Rabeharisoa, 2003). Especially, it examines an informant's narrative of the "wild" search for causation of the disorder by which his family is concerned and the inherent forms and modalities of knowledge production, circulation and validation. While STS scholars have traditionally seen POs as epistemic communities, they currently point out an increasing engagement in such novel forms of collaboration over the last decades. This leads to the emergence of a certain “evidence-based activism” (EBA) among POs, characterized by a growing articulation of credential and more “experiential” knowledge to define common epistemologies of the conditions they are concerned with. The springs of this articulation remain to be explored. Thus, the aim is to flesh out the recent concept of EBA, to empirically question what it covers, and how new biomedical knowledge is generated by “evidence activists”. Rather than provoking “radical openings in technoscientific practice”, our observations show a continuous co-production of knowledge taking place within POs engaged in EBA. So, this paper will take stock of these transformations and envisage the affordances and blind spots for STS of the use of new concepts such as EBA. [less ▲]

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See detailHow to expand method by and for sensory: trials along and beside fieldwork
Vangeebergen, Thomas ULg

Conference (2016, September 01)

In a research with sensory analysts and flavourists, I tried other ways of interview (e.g. people auto-confrontations to their own registered activity) and other mediums to relate to the ethnographical ... [more ▼]

In a research with sensory analysts and flavourists, I tried other ways of interview (e.g. people auto-confrontations to their own registered activity) and other mediums to relate to the ethnographical work, as graphic novel or comics. [less ▲]

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See detailAnalysis of Ocean in Situ Observations and Web - Based Visualization: From Individual Measurements to an Integrated View
Barth, Alexander ULg; Watelet, Sylvain ULg; Troupin, Charles et al

in Diviacco, Paolo; Leadbetter, Adam; Glaves, Helen (Eds.) Oceanographic and Marine Cross-Domain Data Management for Sustainable Development (2016)

The sparsity of observations poses a challenge common to various ocean disciplines. Even for physical parameters where the spatial and temporal coverage is higher, current observational networks ... [more ▼]

The sparsity of observations poses a challenge common to various ocean disciplines. Even for physical parameters where the spatial and temporal coverage is higher, current observational networks undersample a broad spectrum of scales. This situation is generally more severe for chemical and biological parameters because such sensors are less widely deployed. The present chapter describes the analysis tool DIVA (Data-Interpolating Variational Analysis) which is designed to generate gridded fields from in situ observations. DIVA has been applied to various physical (temperature and salinity), chemical (concentration of nitrate, nitrite and phosphate) and biological parameters (abundance of a species). The chapter also shows the technologies used to visualize the gridded fields. Visualization of analyses from in situ observations provide a unique set of challenges since the accuracy of the analysed field is not spatially uniform as it strongly depends on the location of the observations. In addition, an adequate treatment of the depth and time dimensions is essential. [less ▲]

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See detailDes acaricides contre les tiques
Lempereur, Laetitia ULg

Article for general public (2016)

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See detailComparing conventional excellence: moral and technical features of "good research"
Charlier, Nathan ULg

Conference (2016, September)

During a stay at Lancaster University, I was struck to discover how the institutional branding relied on the rhetoric of excellence. Several flags scattered over the campus are displaying statements such ... [more ▼]

During a stay at Lancaster University, I was struck to discover how the institutional branding relied on the rhetoric of excellence. Several flags scattered over the campus are displaying statements such as: "our physicists helped discover the Higgs boson particle", "Lancaster University is ranked among the top 10 universities in the UK", "our volcanologists made the first observation of a rare type of lava", etc. These quotes convey technologies such as rankings, but also moral and epistemological aspects regarding the role and status of scientific knowledge. This fostered my reflection regarding the fieldwork I made in different research institutions located in Belgium: while academic excellence is not at the core of their branding per se, it is indeed a key issue for many actors concerned with research governance. My paper proposes to map the different ways to frame the notion of excellence in four institutions: two large biotech research centres and two universities in Flanders and Wallonia. It relies on 25 semi-structured interviews with tenured academics involved in their institution's research management. The paper will compare how "good research" is valued in different settings: what counts when one evaluates the "excellence" of a scientific production/career? To which technologies, indicators and to which "moral principles" are interviewees referring to when they discuss excellence? How do they engage in criticizing certain framings and praise others? Eligible for the rhetoric or comparative panel, my contribution will present four distinct institutional conventions that govern research practices and sorts the good scientist from the bad. [less ▲]

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See detailL'Expérience, l'Enjeu de Demain
Delcourt, Cécile ULg

Article for general public (2016)

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See detailStudy of Meta-Analysis Strategies for Network Inference using Information-Theoretic Approaches
Pham, Cam Ngoc ULg; Haibe-Kains; Bellot, Pau et al

in IEEE Dexa workshops 2016 (2016, September)

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See detailThe Case : Acute renal failure and refractory hyponatremia
denis, Chloé; JADOT, Virginie ULg; BOUQUEGNEAU, Antoine ULg et al

in Kidney International (2016), 90

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See detailGuide du mémoire
Grandjean, Geoffrey ULg

Learning material (2016)

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See detailBiologie cellulaire: exercices et méthodes
Thiry, Marc ULg; Rigo, Pierre ULg; Racano, Sandra

Book published by Dunod - 2ème édition (2016)

Cet ouvrage propose aux étudiants des premières années d’études supérieures une méthode progressive et conviviale pour comprendre et appliquer les concepts fondamentaux de la biologie cellulaire. À la ... [more ▼]

Cet ouvrage propose aux étudiants des premières années d’études supérieures une méthode progressive et conviviale pour comprendre et appliquer les concepts fondamentaux de la biologie cellulaire. À la suite de rappels de cours, sous forme de fiches, chaque chapitre propose des exercices de difficulté croissante pour s’évaluer : QCM, questions Vrai/Faux et exercices de synthèse. Les corrigés détaillés mettent en évidence la méthodologie. Des ressources numériqes avec des exercices d’entraînement supplémentaires complètent l’ouvrage. Cette nouvelle édition, actualisée, s'enrichit de nouveaux QCM, Vrai/Faux et exercices. [less ▲]

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