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See detailLyot-plane phase masks for improved high-contrast imaging with a vortex coronagraph
Ruane, Garreth J.; Huby, Elsa ULg; Absil, Olivier ULg et al

in Astronomy and Astrophysics (2015), 583

The vortex coronagraph is an optical instrument that precisely removes on-axis starlight allowing for high contrast imaging at small angular separation from the star, thereby providing a crucial ... [more ▼]

The vortex coronagraph is an optical instrument that precisely removes on-axis starlight allowing for high contrast imaging at small angular separation from the star, thereby providing a crucial capability for direct detection and characterization of exoplanets and circumstellar disks. Telescopes with aperture obstructions, such as secondary mirrors and spider support structures, require advanced coronagraph designs to provide adequate starlight suppression. We introduce a phase-only Lyot-plane optic to the vortex coronagraph that offers improved contrast performance on telescopes with complicated apertures. Potential solutions for the European Extremely Large Telescope (E-ELT) are described and compared. Adding a Lyot-plane phase mask relocates residual starlight away from a region of the image plane thereby reducing stellar noise and improving sensitivity to off-axis companions. The phase mask is calculated using an iterative phase retrieval algorithm. Numerically, we achieve a contrast on the order of $10^{-6}$ for a companion with angular displacement as small as $4~\lambda/D$ with an E-ELT type aperture. Even in the presence of aberrations, improved performance is expected compared to either a conventional vortex coronagraph or optimized pupil plane phase element alone. [less ▲]

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See detailLyotard : le déssaisissement de l'art
Steinmetz, Rudy ULg

in L'atelier d'esthétique (Ed.) Esthétique et philosophie de l'art (2002)

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See detailLYP inhibits T-cell activation when dissociated from CSK
Vang; Liu, Wallace H; Delacroix, Laurence ULg et al

in Nature Chemical Biology (2012)

Lymphoid tyrosine phosphatase (LYP) and C-terminal Src kinase (CSK) are negative regulators of signaling mediated through the T-cell antigen receptor (TCR) and are thought to act in a cooperative manner ... [more ▼]

Lymphoid tyrosine phosphatase (LYP) and C-terminal Src kinase (CSK) are negative regulators of signaling mediated through the T-cell antigen receptor (TCR) and are thought to act in a cooperative manner when forming a complex. Here we studied the spatiotemporal dynamics of the LYP–CSK complex in T cells. We demonstrate that dissociation of this complex is necessary for recruitment of LYP to the plasma membrane, where it downmodulates TCR signaling. Development of a potent and selective chemical probe of LYP confirmed that LYP inhibits T-cell activation when removed from CSK. Our findings may explain the reduced TCR-mediated signaling associated with a single-nucleotide polymorphism that confers increased risk for certain autoimmune diseases, including type 1 diabetes and rheumatoid arthritis, and results in expression of a mutant LYP that is unable to bind CSK. Our compound also represents a starting point for the development of a LYP-based treatment of autoimmunity. [less ▲]

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See detailLYRA, a solar UV radiometer on PROBA2
Hochedez; Schmutz, W.; Stockman, Yvan ULg et al

in Advances in Space Research (2006), 37

LYRA is the solar UV radiometer that will embark in 2006 onboard Proba2, a technologically oriented ESA micro-mission. LYRA is designed and manufactured by a Belgian–Swiss–German consortium (ROB, PMOD/WRC ... [more ▼]

LYRA is the solar UV radiometer that will embark in 2006 onboard Proba2, a technologically oriented ESA micro-mission. LYRA is designed and manufactured by a Belgian–Swiss–German consortium (ROB, PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international collaborations. It will monitor the solar irradiance in four UV passbands. They have been chosen for their relevance to Solar Physics, Aeronomy and Space Weather: (1) the 115–125 nm Lyman-a channel, (2) the 200–220 nm Herzberg continuum range, (3) the Aluminium filter channel (17–70 nm) including He II at 30.4 nm and (4) the Zirconium filter channel (1–20 nm). The radiometric calibration will be traceable to synchrotron source standards (PTB and NIST). The stability will be monitored by onboard calibration sources (LEDs), which allow to distinguish between potential degradations of the detectors and filters. Additionally, a redundancy strategy maximizes the accuracy and the stability of the measurements. LYRA will benefit from wide bandgap detectors based on diamond: it will be the first space assessment of a pioneering UV detectors program. Diamond sensors make the instruments radiation-hard and solar-blind: their high bandgap energy makes them insensitive to visible light and, therefore, make dispensable visible light blocking filters, which seriously attenuate the desired ultraviolet signal. Their elimination augments the effective area and hence the signal-to-noise, therefore increasing the precision and the cadence. The SWAP EUV imaging telescope will operate next to LYRA on Proba2. Together, they will establish a high performance solar monitor for operational space weather nowcasting and research. LYRA demonstrates technologies important for future missions such as the ESA Solar Orbiter [less ▲]

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See detailLa lyre anthropomorphe C.94 de Vienne. Un instrument emblématique de la Renaissance italienne
Bugini, Mariaelena ULg

Scientific conference (2017, April 18)

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See detailLyrical Cartographies: Re-Drawing the Boundaries of the Black Atlantic in Dionne Brand's A Map to the Door of No Return and At the Full and Change of the Moon
Mergeai, Mathilde ULg

in Durán Almarza, Liamar; Álvarez López, Esther (Eds.) Diasporic Women's Writing of the Black Atlantic: (En)Gendering Literature and Performance (2014)

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See detailLyrics, Music and Voice: a Comparative Semiotics of Emotions in Cole Porter's "Miss Otis Regrets"
Lindenberg Lemos, Carolina ULg

Conference (2012, June 27)

What makes for an engaging song? One may credit the lyrics, another the melody, but in fact the two components are indissociable (Tatit, 2007). In Cole Porter's “Miss Otis Regrets”, we are introduced to ... [more ▼]

What makes for an engaging song? One may credit the lyrics, another the melody, but in fact the two components are indissociable (Tatit, 2007). In Cole Porter's “Miss Otis Regrets”, we are introduced to the sad account of Miss Otis. The lyrics give us fragments of her story but not from her point of view. How, then, do we relate to her tragedy? In this paper, a comparative semiotic approach to lyrics, music, and voice will be used to demonstrate the narrator is key to this process. It is from the latter's point of view that we approach the story. First, an analysis of the linguistic component, based on Greimas (1983; 1987) and Zilberberg (1988; 2006), will show how the choice of vocabulary and repetitions subtly disagree with the values assumed by the community that condemns Miss Otis. However, non-linguistic components also play a central role. Following Tatit's (1997; 2007) proposals for the semiotic approach to songs, we will investigate how Porter's choices of accents, elongations and the exploration of pitch range emphasize the points that are most filled with emotions in the narrative. Melody and lyrics are shown to work together in the construction of the emotional connotations. Nonetheless, it is only when it is no longer in paper, but in the form of an actual execution, that the song may be said to move. We then explore the well-known rendition of Ella Fitzgerald. Despite the accompanying piano, we focus here on the voice as the place where linguistic and musical components meet. Our analysis compares the recording and the original score in order to assess the level of adequacy and change that the interpreter promoted. Variations in notes, stress, and rhythm may be shown to change the original direction dramatically, while others offer accentuated distinctions that were already in place. In all cases, the singer’s transformations take the song a step further in its emotional contents. Adopting this comparative semiotic approach, we reestablish the chain that extracts the emotions from the narrative, to the music, and to the voice, showing that the path that ensures the emotional attachment of the listener is in the integration of the three components: lyrics, music, and voice. References: Greimas, A. J. (1983). “De la colère: étude de sémantique lexicale” In: Du sens II. Paris: Seuil, p. 225-246. __________ (1987). De l'imperfection. Périgueux: Fanlac. Tatit, L. (1997). Musicando a Semiótica: Ensaios. São Paulo: Annablume. __________ (2007). Semiótica da Canção: Melodia e Letra. São Paulo: Escuta. Zilberberg, C. (1988). Raison et poétique du sens. Paris: PUF. __________ (2006). Eléments de grammaire tensive. Limoges: Pulim. [less ▲]

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See detailThe Lys-Asp-Tyr Triad within the Mite Allergen Der p 1 Propeptide Is a Critical Structural Element for the pH-Dependent Initiation of the Protease Maturation.
Chevigne, Andy; Campizi, Vincenzo; Szpakowska, Martyna et al

in International Journal of Molecular Sciences (2017), 18(5),

The major house dust mite allergen, Der p 1, is a papain-like cysteine protease expressed as an inactive precursor, proDer p 1, carrying an N-terminal propeptide with a unique structure. The maturation of ... [more ▼]

The major house dust mite allergen, Der p 1, is a papain-like cysteine protease expressed as an inactive precursor, proDer p 1, carrying an N-terminal propeptide with a unique structure. The maturation of the zymogen into an enzymatically-active form of Der p 1 is a multistep autocatalytic process initiated under acidic conditions through conformational changes of the propeptide, leading to the loss of its inhibitory ability and its subsequent gradual cleavage. The aims of this study were to characterize the residues present in the Der p 1 propeptide involved in the initiation of the zymogen maturation process, but also to assess the impact of acidic pH on the propeptide structure, the activity of Der p 1 and the fate of the propeptide. Using various complementary enzymatic and structural approaches, we demonstrated that a structural triad K17p-D51p-Y19p within the N-terminal domain of the propeptide is essential for its stabilization and the sensing of pH changes. Particularly, the protonation of D51p under acidic conditions unfolds the propeptide through disruption of the K17p-D51p salt bridge, reduces its inhibition capacity and unmasks the buried residues K17p and Y19p constituting the first maturation cleavage site of the zymogen. Our results also evidenced that this triad acts in a cooperative manner with other propeptide pH-responsive elements, including residues E56p and E80p, to promote the propeptide unfolding and/or to facilitate its proteolysis. Furthermore, we showed that acidic conditions modify Der p 1 proteolytic specificity and confirmed that the formation of the first intermediate represents the limiting step of the in vitro Der p 1 maturation process. Altogether, our results provide new insights into the early events of the mechanism of proDer p 1 maturation and identify a unique structural triad acting as a stabilizing and a pH-sensing regulatory element. [less ▲]

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See detailLys13 plays a crucial role in the functional adaptation of the thermophilic triose-phosphate isomerase from Bacillus stearothermophilus to high temperatures
Alvarez, Marco; Wouters, Johan; Maes, Dominique et al

in Journal of Biological Chemistry (1999), 274(27), 19181-7

The thermophilic triose-phosphate isomerases (TIMs) of Bacillus stearothermophilus (bTIM) and Thermotoga maritima (tTIM) have been found to possess a His12-Lys13 pair instead of the Asn12-Gly13 pair ... [more ▼]

The thermophilic triose-phosphate isomerases (TIMs) of Bacillus stearothermophilus (bTIM) and Thermotoga maritima (tTIM) have been found to possess a His12-Lys13 pair instead of the Asn12-Gly13 pair normally present in mesophilic TIMs. His12 in bTIM was proposed to prevent deamidation at high temperature, while the precise role of Lys13 is unknown. To investigate the role of the His12 and Lys13 pair in the enzyme's thermoadaptation, we reintroduced the "mesophilic residues" Asn and Gly into both thermophilic TIMs. Neither double mutant displayed diminished structural stability, but the bTIM double mutant showed drastically reduced catalytic activity. No similar behavior was observed with the tTIM double mutant, suggesting that the presence of the His12 and Lys13 cannot be systematically correlated to thermoadaptation in TIMs. We determined the crystal structure of the bTIM double mutant complexed with 2-phosphoglycolate to 2.4-A resolution. A molecular dynamics simulation showed that upon substitution of Lys13 to Gly an increase of the flexibility of loop 1 is observed, causing an incorrect orientation of the catalytic Lys10. This suggests that Lys13 in bTIM plays a crucial role in the functional adaptation of this enzyme to high temperature. Analysis of bTIM single mutants supports this assumption. [less ▲]

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See detailA lysine cluster in domain II of Bacillus subtilis PBP4a plays a role in the membrane attachment of this C1 PBP.
Vanden Broeck, Arnaud; Dauvin, Marjorie ULg; Sauvage, Eric et al

Poster (2015, June 08)

Bacillus subtilis PBP4a belongs to the class-C1 PBPs characterized by two internal additional domains of unknown function. Seven lysine residues (K) are protruding from domain II. Four of them: K86, K114 ... [more ▼]

Bacillus subtilis PBP4a belongs to the class-C1 PBPs characterized by two internal additional domains of unknown function. Seven lysine residues (K) are protruding from domain II. Four of them: K86, K114, K119 and K265 have been mutated in glutamine residues (Q). Both proteins (WT and Mut4KQ PBP4a) have been produced without signal peptide in E. coli and their sub-cellular localizations determined by measuring the DD-carboxypeptidase activities in the different compartments (cytoplasmic vs membrane attached proteins). After purification, their binding to B. subtilis membranes has been compared: WT PBP4a interacts in vitro with membranes isolated from this organism in contrast to Mut4KQ PBP4a that remains entirely unbound. In absence of any amphiphilic peptide in PBP4a, the crown of positive charges on the surface of domain II is likely responsible for the PBP cellular localization in interaction with the cytoplasmic membrane. [less ▲]

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See detailA lysine cluster in domain II of Bacillus subtilis PBP4a plays a role in the membrane attachment of this C1-PBP
Vanden Broeck, Arnaud; Van Der Heiden, Edwige ULg; Sauvage, Eric ULg et al

in PLoS ONE (2015)

In PBP4a, a Bacillus subtilis class-C1 penicillin-binding protein (PBP), four clustered lysine (K) residues, K86, K114, K119, and K265, protrude from domain II. Replacement of these amino acids with ... [more ▼]

In PBP4a, a Bacillus subtilis class-C1 penicillin-binding protein (PBP), four clustered lysine (K) residues, K86, K114, K119, and K265, protrude from domain II. Replacement of these amino acids with glutamine (Q) residues by site-directed mutagenesis yielded Mut4KQ PBP4a. When produced in Escherichia coli without its predicted Sec-signal peptide, wildtype (WT) PBP4a was found mainly associated with the host cytoplasmic membrane, whereas Mut4KQ PBP4a remained largely unbound. After purification, the capacities of the two proteins to bind to B. subtilis membranes were compared. The results were similar to those obtained in E. coli: in vitro, a much higher percentage of WT PBP4a than of Mut4KQ PBP4a was found to interact with B. subtilis membranes. Immunodetection of PBP4a in B. subtilis membrane extracts revealed that a processed form of this PBP (as indicated by its size) associates with the B. subtilis cytoplasmic membrane. In the absence of any amphiphilic peptide in PBP4a, the crown of positive charges on the surface of domain II is likely responsible for the cellular localization of this PBP and its attachment to the cytoplasmic membrane. [less ▲]

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See detailLysosomal phospholipases inhibition by emetine, strychnopentamine and usambarensine
Quetin-Leclercq, Joelle; Schomer, G; Van Bambeke, F et al

Poster (1999)

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See detailLysozyme gene activity in chicken macrophages is controlled by positive and negative regulatory elements.
Steiner, Christoph; Muller, Marc ULg; Baniahmad, Aria et al

in Nucleic Acids Research (1987), 15(10), 4163-78

The chicken lysozyme gene is constitutively active in macrophages and under the control of steroid hormones in the oviduct. To investigate which DNA elements are involved in the control of its expression ... [more ▼]

The chicken lysozyme gene is constitutively active in macrophages and under the control of steroid hormones in the oviduct. To investigate which DNA elements are involved in the control of its expression in macrophages we performed transient DNA transfer experiments with two different types of plasmids: 5'-deletion mutants of the upstream region of the chicken lysozyme gene and different fragments from this area in front of the thymidine kinase promoter (herpes simplex virus), each placed in front of the CAT (chloramphenicol acetyl transferase) coding sequence. Two enhancers (E-2.7 kb and E-0.2 kb) were characterized. They are active in macrophages, but not in chicken fibroblasts. Furthermore a negative element (N-2.4 kb) was identified, which is active in fibroblasts and promyelocytes, but not in mature macrophages. The combined action of all three elements contributes to the observed lysozyme gene activities: no activity in fibroblasts, moderate activity in promyelocytes and high activity in mature macrophages. [less ▲]

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See detailLʼétalement urbain en Europe : un défi environnemental ignoré
Halleux, Jean-Marie ULg

Article for general public (2007)

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See detailLʼimmobilier de bureau en Belgique, un révélateur des mutations économiques et urbaines ?
Bruck, L.; Mairy, N.; Halleux, Jean-Marie ULg et al

in Bulletin de la Société Géographique de Liège (2005), 46

The aim of the paper is to analyse how office markets are in interaction with the evolutions in the field of territory and economy. The first part of the paper analyses the data available to study the ... [more ▼]

The aim of the paper is to analyse how office markets are in interaction with the evolutions in the field of territory and economy. The first part of the paper analyses the data available to study the office stocks. Afterwards, we present an urban hierarchy based on the office equipment, in relation with the process of metropolization and its location consequences. The last part of the paper shows that the office function is also concerned with the process of periurbanization. [less ▲]

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See detailM Cushing : a life long experience with pituitary surgery
Beckers, Albert ULg

Scientific conference (2008, October 07)

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See detailM- Service Value Perceptions and Customer Loyalty
Pihlstrom, M.; Liljander, V.; Van Riel, Allard ULg

Poster (2008, July 14)

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See detailM-Ingestion: Simultaneous Ingestion of Ionosonde and GNSS Data into the NeQuick Model
Bidaine, Benoît ULg; Nava, Bruno; Stankov, Stanimir et al

in Doherty, P.; Hernández-Pajares, M.; Juan, J.-M. (Eds.) et al The International Beacon Satellite Symposium BSS2010 (2010, June)

The steady increase in volume and quality of ionospheric measurements allows for potential improvements in the existing ionospheric models. In particular ionosonde and Global Navigation Satellite Systems ... [more ▼]

The steady increase in volume and quality of ionospheric measurements allows for potential improvements in the existing ionospheric models. In particular ionosonde and Global Navigation Satellite Systems (GNSS) data provide complementary information for original developments regarding the NeQuick model, a quick-run empirical model of the electron density supplying flexible solutions for various applications. Indeed NeQuick is often used to investigate radiowave propagation issues: among others it has been implemented within the Galileo Single Frequency Ionospheric Correction Algorithm. The model is particularly suited to be used within an optimization procedure called ingestion. In this framework, an "effective ionization level" Az plays the role of solar activity input in order to fit a specific dataset eg of slant Total Electron Content (TEC). However larger discrepancies can then obviously be observed towards other parameters eg the F2-layer critical frequency foF2. This draws the interest for a multiple ingestion - or m-ingestion - scheme implying an adaptation towards several datasets by defining several effective parameters. In our study, we perform m-ingestion of ionosonde and GNSS data providing us with slant TEC. In fact it allows us to constrain the electron density profile slab thickness. For the purpose, a high solar activity period (year 2002) was analysed based on collocated digisonde and EUREF GNSS observations at a mid-latitude site, Dourbes (50.1◦N, 4.6◦E). In this way, we can gather some clues on expected ionospheric effects on Galileo applications during the next solar activity maximum. [less ▲]

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See detailM-N interaction in beam-to-column joints - Development of a design model
Demonceau, Jean-François ULg; Jaspart, Jean-Pierre ULg

in Zingoni, Alphose (Ed.) Proceedings of the SEMC 2010 International Conference (2010, September 06)

The component method is a nowadays widely recognized procedure for the evaluation of the design properties of structural joints. It is used as a reference method in the Eurocodes and the proposed rules in ... [more ▼]

The component method is a nowadays widely recognized procedure for the evaluation of the design properties of structural joints. It is used as a reference method in the Eurocodes and the proposed rules in these codes are mainly devoted to the characterization of joints subjected to bending moments and shear forces. However, in some situations, these joints can be subjected to combined axial loads and bending mo-ments, for instance in frames subjected to an exceptional event leading to the loss of a column, situation where significant tying forces can developed in the structural beams above the lost column. In this paper, a design model, founded on the component method, aiming at predicting the behaviour of joints subjected to com-bined axial loads and bending moments is presented. In particular, it is illustrated how this model was vali-dated through comparisons to recent experimental tests performed on steel-concrete composite beam-to-column joints. [less ▲]

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See detailM-type channels selectively control bursting in rat dopaminergic neurons
Drion, Guillaume ULg; Bonjean, Maxime; Waroux, Olivier ULg et al

in European Journal of Neuroscience (2010), 31

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