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See detailNon-destructive measurements of the volume magnetic behavior of large bulk GdBCO single domains and ferromagnet/superconductor structures
Vanderbemden, Philippe ULg; Egan, Raphael; Morita, Mitsuru et al

Conference (2016, September 05)

The present work deals with magnetic measurements on bulk large grain GdBa2Cu3O7 (GdBCO) single domains using a recently constructed bespoke magnetometer [Rev. Sci. Instrum. 86 025107 (2015)]. The device ... [more ▼]

The present work deals with magnetic measurements on bulk large grain GdBa2Cu3O7 (GdBCO) single domains using a recently constructed bespoke magnetometer [Rev. Sci. Instrum. 86 025107 (2015)]. The device enables the measurement of magnetic moments as large as 1 Am^2 (1000 emu) on large bulk samples up to 20 mm diameter at 77 K. This extends significantly the accessible measurement range of “off-the shelf” magnetometers (e.g. SQUID, VSM). Unlike Hall probe mapping, the measured signal is representative of the superconducting currents flowing across the entire height of the sample. Since the device is based on a flux extraction technique and does not include any Hall probe, another advantage is that no gap between a Hall probe and the sample needs to be taken into account to interpret the results. In the present work we first show how the dimensions of the sensing coils and integration bounds are chosen in such a way the magnetometer is sensitive to dipolar magnetic moment of the sample, while being insensitive to moments of higher order. Next we study the relaxation of the trapped magnetic moment under various magnetization processes. The sensitivity of the device allows small variations of m (e.g. ~ 2% for 1 hour) to be recorded. We show experimentally that the relaxation of the magnetic moment of the whole sample is reduced strongly if the superconductor is not fully magnetized, either in field cooled (FC) or zero-field cooled (ZFC) conditions. The practical consequence is that an abnormally slow magnetic relaxation (large E-J power law exponent n) under a conventional magnetization procedure indicates that the bulk superconductor could be magnetized further. In a second set of experiments, we study the increase of magnetic moment of a bulk superconductor when it is attached to a soft ferromagnetic disk. We also examine the irreversible demagnetization of these structures when subjected to crossed magnetic fields and compare to the magnetic moment of a classical (Nd-Fe-B) permanent magnets in the same conditions. Acknowledgements: This work is part of an "Action de Recherches Concertees" grant (ARC 11/16 -03) from the "Communaute Francaise de Belgique". [less ▲]

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See detailPhase Slips In Tunable Width Point Contacts Created By Electromigration
Silhanek, Alejandro ULg

Conference (2016, September 05)

Superconducting nanowires have been, for years now, a topic of great interest due to their potential application in single photon detectors and as interconnects in circuits proposed for quantum computing ... [more ▼]

Superconducting nanowires have been, for years now, a topic of great interest due to their potential application in single photon detectors and as interconnects in circuits proposed for quantum computing. 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 as a function of the wire width. In this presentation, we explore in-situ controlled electromigration (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. We also demonstrate that the bow-tie shaped constrictions exhibit a negative magnetoresistance at low magnetic fields which can be attributed to the suppression of superconductivity in the contact leads. Strikingly, the detrimental effect caused by the repeated EM can be healed by simply inverting the current direction. These findings reveal perspectives of the proposed fabrication method for exploring various fascinating superconducting phenomena in atomic size constrictions. [less ▲]

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See detailSeasonal variability of surface and column carbon monoxide over megacity Paris, high-altitude Jungfraujoch and Southern Hemispheric Wollongong stations
Té, Y; Jeseck, P; Franco, Bruno ULg et al

in Atmospheric Chemistry and Physics (2016), 16

This paper studies the seasonal variation of surface and column CO at three different sites (Paris, Jungfraujoch and Wollongong), with an emphasis on establishing a link between the CO vertical ... [more ▼]

This paper studies the seasonal variation of surface and column CO at three different sites (Paris, Jungfraujoch and Wollongong), with an emphasis on establishing a link between the CO vertical distribution and the nature of CO emission sources. We find the first evidence of a time lag between surface and free tropospheric CO seasonal variations in the Northern Hemisphere. The CO seasonal variability obtained from the total columns and free tropospheric partial columns shows a maximum around March–April and a minimum around September–October in the Northern Hemisphere (Paris and Jungfraujoch). In the Southern Hemisphere (Wollongong) this seasonal variability is shifted by about 6 months. Satellite observations by the IASI–MetOp (Infrared Atmospheric Sounding Interferometer) and MOPITT (Measurements Of Pollution In The Troposphere) instruments confirm this seasonality. Ground-based FTIR (Fourier transform infrared) measurements provide useful complementary information due to good sensitivity in the boundary layer. In situ surface measurements of CO volume mixing ratios at the Paris and Jungfraujoch sites reveal a time lag of the near-surface seasonal variability of about 2 months with respect to the total column variability at the same sites. The chemical transport model GEOS-Chem (Goddard Earth Observing System chemical transport model) is employed to interpret our observations. GEOS-Chem sensitivity runs identify the emission sources influencing the seasonal variation of CO. At both Paris and Jungfraujoch, the surface seasonality is mainly driven by anthropogenic emissions, while the total column seasonality is also controlled by air masses transported from distant sources. At Wollongong, where the CO seasonality is mainly affected by biomass burning, no time shift is observed between surface measurements and total column data. [less ▲]

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See detailImprinting superconducting vortex trajectories in a magnetic layer
Shaw, Gorky ULg

Conference (2016, September 05)

We experimentally show that the principle of local polarization of a magnetic layer can be applied for imprinting, into a soft magnetic layer of permalloy (Py), the trajectory of vortices moving in a ... [more ▼]

We experimentally show that the principle of local polarization of a magnetic layer can be applied for imprinting, into a soft magnetic layer of permalloy (Py), the trajectory of vortices moving in a superconducting film (Nb). In full analogy with a magnetic drawing board, vortices act as tiny magnetic scribers leaving a wake of polarized magnetic media in the Py layer. We have used the magneto-optical imaging technique to investigate the mutual interaction between superconducting vortices and ferromagnetic domains. In general, we observe that the flux propagation is delayed at the border of the magnetic layer. For thick Py layers, the stripe magnetic domain pattern guides the smooth flux penetration as well as the abrupt vortex avalanches in the Nb film. More interestingly, in thin Py layers without stripe domains, vortices leave clear imprints of locally polarized magnetic moments along their trajectories. Furthermore, the printings were found to be stable and could still be observed at room temperature, allowing for ex situ observation of the flux penetration in superconductors. We expect our findings to pave the way for further studies for optimizing magnetic recording of superconducting vortex trajectories. [less ▲]

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See detailBalanced words and related concepts: applications and complexity issues
Crama, Yves ULg

Conference (2016, September 05)

In this talk, I present a few results and several questions about "regular" sequences of integers and related concepts, such as balanced words, partitions and covers of the integers by arithmetic ... [more ▼]

In this talk, I present a few results and several questions about "regular" sequences of integers and related concepts, such as balanced words, partitions and covers of the integers by arithmetic sequences. Such concepts have been investigated in pure mathematics, but also naturally arise in a variety of application fields such as production planning, political science, or queueing theory. I briefly present some of these applications and explain how they motivate seemingly new questions relating, for instance, to the algorithmic complexity of regular partitions, or to the structure of balanced words. The presentation is based on joint work with Nadia Brauner and Vincent Jost (Grenoble). [less ▲]

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See detailFlipped classes and enriched skeleton maps to foster deep and interactive learning in engineering education
Attia, Shady ULg; Detroz, Pascal ULg

in Mazijn (Ed.) BUILDING A CIRCULAR ECONOMY TOGETHER (2016, September 05)

This paper reports the initial experience of applying the enriched skeleton mapping technique as innovative and meaningful learning methods within a flipped class teaching setting. Driven by the low ... [more ▼]

This paper reports the initial experience of applying the enriched skeleton mapping technique as innovative and meaningful learning methods within a flipped class teaching setting. Driven by the low confidence and autonomy of many undergraduates; this study focus on stimulating collaboration and interactive learning. The study was performed in a course labeled ‘sustainable building construction technology’ of the Bachelor of Architectural Engineering program at Liege University (Ulg). First year and second year students, were assigned to an experimental group of 27 students and a control group of 8. In the experimental group, students worked together in pairs on mini-concepts and created enriched skeleton maps for the course content. The control group received a regular ex-cathedra course. The results show that students who used the enriched skeleton mapping technique were more engaged and outperformed the control group. Enriched skeleton concept mapping fostered deep learning and resulted in a better understanding of the course mini concepts in addition to the course structure and domain. Students of the enriched skeleton mapping found learning to be more ‘useful, stimulating and more engaging’, whereas students of the congenital ex-cathedra curriculum found learning to be ‘passive and boring’. A combination of both techniques may provide the most effective training for undergraduate engineering students. [less ▲]

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See detailFeeding ecology of Southern Ocean seastars inferred from stable isotopes ratios
Le Bourg, Baptiste ULg; Blanchard, Alice; Danis, Bruno et al

Poster (2016, September 05)

The Southern Ocean is currently subjected to strong and contrasted impacts of climate change. The Western Antarctic Peninsula is one of the most rapidly warming regions of the world, resulting in sea ice ... [more ▼]

The Southern Ocean is currently subjected to strong and contrasted impacts of climate change. The Western Antarctic Peninsula is one of the most rapidly warming regions of the world, resulting in sea ice cover decreases. Increasing seawater temperature and sea ice cover reduction in Western Antarctic Peninsula and associated regions will likely impact food web functioning through temperature-related changes in consumer physiology, modifications of benthic community structure (e.g. expansion of exogenous species such as predatory crabs), modifications of benthic-pelagic coupling intensity or disruption of benthic production. Asteroids (Echinoderms) are an important group of southern benthos. This group also has a great trophic variability and is potentially more resistant than other organisms to temperature changes (Peck et al. 2008). Consequently, they will be likely impacted by modifications in food webs functioning rather by direct warming and investigating their trophic ecology is necessary to infer how climate change will impact them. In this context, the aim of this study is to use stable isotopes ratios of C, N and S to infer sea stars trophic ecology. 16 species of sea stars spanning 10 different families sampled in multiple and contrasted habitats across Subantarctic (South Georgia, South Sandwich Islands, Falkland Islands) and Antarctic (South Shetland Islands, South Orkney Islands, Western Antarctic Peninsula) locations. In total, tegument samples from 213 specimens was analysed. Diversity and plasticity of asteroid diet along Southern Ocean coasts were explored through isotopic niche parametrisation (e.g. niche width and overlap between species and/or populations; Jackson et al. 2011). The data will also be used in a larger scale research project on the trophic ecology of Antarctic sea stars. This project will notably compare trophic resources supporting asteroid communities in Western Antarctic Peninsula, where sea ice cover is decreasing, and in Terre Adélie, where sea ice cover is increasing (Parkinson & Cavalieri 2012). Ultimately, this project will help understanding which ecological processes determine how an animal group copes with environmental modifications linked to climate change. [less ▲]

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See detailNew crystallographic data on several uranyl minerals
Dal Bo, Fabrice ULg; Hatert, Frédéric ULg; Philippo, Simon

Conference (2016, September 04)

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See detailGrazing practices, perception and expectations of Walloon dairy farmers
Lessire, Françoise ULg; Bernard, Maxime; Lioy, Rocco et al

in Högling, Mats; Bakken, Anne Kjersti; Hovstad, Knut Anders (Eds.) et al The multiple roles of grassland in the European bioecnomy (2016, September 04)

The role of grasslands as a C sink is generally accepted. It is considered that permanent grasslands allow annual C storage rates between 22 and 44 g C/m2/y (Soussana et al., 2010) thereby contributing to ... [more ▼]

The role of grasslands as a C sink is generally accepted. It is considered that permanent grasslands allow annual C storage rates between 22 and 44 g C/m2/y (Soussana et al., 2010) thereby contributing to the mitigation of greenhouse gas (GHG) emissions. Grassland preservation has several other advantages including a decrease in feeding costs (Dillon et al., 2005), a positive effect on cows’ health (e.g.a decrease in lameness) (Burow et al., 2011) and the provision of a positive image to consumers. Despite these arguments, grazing is decreasing in Europe and grasslands are disappearing. A better understanding of grazing practices and of farmers’ expectations could suggest ways of improving these practices and limiting grassland disappearance. As a result, Walloon dairy farmers were surveyed in December 2015 and the preliminary results are presented below. [less ▲]

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See detailBack on Track... in 3D
Marchal, Antoine ULg; Lejeune, Philippe ULg; De Bruyn, Nico

Poster (2016, September 04)

Ecological monitoring provides basic information on population status and distribution that is crucial for conservation, research and management strategies. Studies using tracks are controversial due to ... [more ▼]

Ecological monitoring provides basic information on population status and distribution that is crucial for conservation, research and management strategies. Studies using tracks are controversial due to past misuses tainted with subjectivity. Advances in photogrammetry literally add another dimension to the recording techniques, and geometric morphometrics provides an appropriate approach for the study of track shape variation. Tracks are back on track in conservation! [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 detailNourrir à l’herbe : principales règles nutritionnelles pour réussir
Beckers, Yves ULg

Conference given outside the academic context (2016)

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See detailUrban soils with a sideway glance
Meulemans, Germain ULg

Conference (2016, September 03)

The soils of cities are becoming an important subject for the soil sciences, triggering revisions in their usual modes of research and concepts. One implication of this is the resort to the 'ecological ... [more ▼]

The soils of cities are becoming an important subject for the soil sciences, triggering revisions in their usual modes of research and concepts. One implication of this is the resort to the 'ecological engineering' of soils, framed as a research in soil processes through the active making of soils from scratch. In this, several voices from inside the Soil sciences call for a move from descriptive research to open-ended experimentation. A similar move has also been called for in anthropology. Ingold, notably, suggests to revive the 'craft of anthropology' (2008), encouraging anthropologists to participate in the carrying on of life through craft and experimentation, rather than restraining to retrospective accounts of its unfolding dynamics. How, then, can turns towards making resonate between the practices of soil scientists and those of the anthropologists that attempt to study them? In this paper, I present a collaborative experiment between artists, anthropologists and soil scientists that was carried out in a series of residences near Paris between 2015 and 2016. The residential sessions consisted in a continuation and speculative exploration of the questions raised in both the soil sciences and anthropology in an experimental, creative way - addressing the intertwinement of human and soil becomings from direct engagement with them. The paper addresses how such experiments can be a research process, aimed at exploring the world 'with a sideway glance' (Ingold, 2008). The paper concludes with open questions on where anthropological investigation through art making might play a role in the future of disciplinarities. [less ▲]

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See detailAssessing Basic Motor Competencies in Primary School – an International Comparative Study in Europe
Scheuer, Claude; Cloes, Marc ULg; Colella, Dario et al

Conference (2016, September 03)

A central aim of primary physical education (PE) is the promotion of physical competencies as a necessary condition of developing a physically active lifestyle and to be able to participate in the Olympic ... [more ▼]

A central aim of primary physical education (PE) is the promotion of physical competencies as a necessary condition of developing a physically active lifestyle and to be able to participate in the Olympic community. We defined basic motor competencies as physical performance dispositions, which evolved from task-specific requirements in the culture of sports and exercise. They are supposed to be learnable, based on previous experiences and can be improved through practice. Potential evaluations of effects in PE need to consider situation-specific and context-dependent characteristics of PE as well as prior experiences of pupils. Therefore, a design for test items, which are closely related to PE and vary in difficulty depending on the age of the pupils, is necessary. For this purpose, we developed the MOBAK-1 test instrument for the assessment of basic motor competencies in first graders. It allows teachers to identify groups in need of special support, and initiate these support measures to reduce inequalities. The first study took place in Zurich (Switzerland) and focused on construct validity (e.g., the factorial validity of the instrument). Between spring 2015 and spring 2016, the MOBAK-1 test instrument was and will be implemented in further countries in Europe. At this time, we have four samples of four different countries: (1) Switzerland (Zurich) (N = 317; girls = 55%; age: M = 7.04 years [SD = .37]; BMI = 16.08 [SD = 2.25]) assessed by University of Basel (Dr. Christian Herrmann); (2) Germany (Frankfurt) (N = 1061; girls = 45%; age: M = 6.80 years [SD = .89]; BMI = 16.30 [SD = 2.37]) assed by University of Frankfurt (Prof. Dr. Christopher Heim); (3) Lithuania (Kaunas) (N = 120; girls = 48%; age: M = 7.76 years [SD = .33]; BMI = 16.14 [SD = 2.30]) assessed by Lithuanian Sports University (Assoc. Prof. Dr. Arunas Emeljanovas); (4) Italy (Foggia) (N = 85; girls = 45%; age: M = 7.24 years [SD = .30]; BMI = 17.53 [SD = 3.04]) assessed by University of Foggia (Prof. Dr. Dario Colella). Further samples are currently on the way to be completed in four other countries: (1) Luxembourg (N = 280) assessed by University of Luxembourg (Claude Scheuer); (2) Slovakia (Trnava) (N = 240) assessed by University of Trnava (Dr. Dana Masarykova); (3) Czech Republic (Brno) (N = 600) assessed by University of Brno (Dr. Petr Vlcek); (4) Belgium (Liège) (N = 450) assessed by University of Liège (Prof. Dr. Marc Cloes and Dr. Boris Jidovtseff). In the initial validation study in Switzerland, two factors consisting of four items each were found. The related EFA (Study 1: CFI=.98; RMSEA=.024) and CFA (Study 2: CFI =.95; RMSEA=.044) revealed good model fit indices. The first factor “Locomotion” represents body movements (e.g., balancing), the second factor “Object-control” represents ball control (e.g., catching). Conclusions: The developed MOBAK test instrument meets psychometric validity demands based on the Swiss data. The presentation will show the results of the validation studies in further European countries and the results of the comparative study. [less ▲]

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See detailVibrations in the Flat Land- A Study of the Vibrational Properties of the Transition-Metal Dichalcogenides
Pike, Nicholas ULg; Dewandre, Antoine ULg; Verstraete, Matthieu ULg et al

Scientific conference (2016, September 03)

Calculations of the vibrational properties of the transition-metal dichalcoginides depend critically on the lattice parameters, symmetries of the underlying system, and the non-local dispersive ... [more ▼]

Calculations of the vibrational properties of the transition-metal dichalcoginides depend critically on the lattice parameters, symmetries of the underlying system, and the non-local dispersive interaction. Here we present phonon band structure calculations, dielectric tensors, elastic tensors, and Born Effective Charges for the transition-metal dichalcogenides $MoS_2$, $MoSe_2$, $MoTe_2$, $WS_2$, $WSe_2$, $NbS_2$, and $NbSe_2$. We systematically investigate the role of the long-range $e^⁻$-$e^⁻$ interaction, spin-orbit coupling, and pseudo-potential approximation, and highlight their importance on the TMD structural and vibrational properties. We find that the phonon spectrum, calculated with the help of a Grimme's D3 non-local Van der Waals interaction depends strongly on the accuracy of the lattice parameters and slightly on the addition of the non-local Van der Waals interaction in the phonon frequency itself. We also find that the sign of the Born Effective Charges on each atom in the Hexagonal TMDs are the opposite of similarly structured compounds. We explore reasons as to why this occurs. Additionally, our calculation of the dielectric tensor and elastic tensor allow us to describe the mechanical properties of the system which are necessary to know for future device applications. [less ▲]

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See detail“That’s only statistics”:Recording PPPs in national accounts
Piron, Damien ULg

Conference (2016, September 02)

Detailed reference viewed: 21 (2 ULg)