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See detailApplication of GRACE to the assessment of model-based estimates of monthly Greenland Ice Sheet mass balance (2003–2012)
Schlegel, N.; Wiese, D.; Larour, E. et al

in Cryosphere (The) (2016), 10

Quantifying the Greenland Ice Sheet's future contribution to sea level rise is a challenging task that requires accurate estimates of ice sheet sensitivity to climate change. Forward ice sheet models are ... [more ▼]

Quantifying the Greenland Ice Sheet's future contribution to sea level rise is a challenging task that requires accurate estimates of ice sheet sensitivity to climate change. Forward ice sheet models are promising tools for estimating future ice sheet behavior, yet confidence is low because evaluation of historical simulations is challenging due to the scarcity of continental-wide data for model evaluation. Recent advancements in processing of Gravity Recovery and Climate Experiment (GRACE) data using Bayesian-constrained mass concentration ("mascon") functions have led to improvements in spatial resolution and noise reduction of monthly global gravity fields. Specifically, the Jet Propulsion Laboratory's JPL RL05M GRACE mascon solution (GRACE_JPL) offers an opportunity for the assessment of model-based estimates of ice sheet mass balance (MB) at ∼ 300 km spatial scales. Here, we quantify the differences between Greenland monthly observed MB (GRACE_JPL) and that estimated by state-of-the-art, high-resolution models, with respect to GRACE_JPL and model uncertainties. To simulate the years 2003–2012, we force the Ice Sheet System Model (ISSM) with anomalies from three different surface mass balance (SMB) products derived from regional climate models. Resulting MB is compared against GRACE_JPL within individual mascons. Overall, we find agreement in the northeast and southwest where MB is assumed to be primarily controlled by SMB. In the interior, we find a discrepancy in trend, which we presume to be related to millennial-scale dynamic thickening not considered by our model. In the northwest, seasonal amplitudes agree, but modeled mass trends are muted relative to GRACE_JPL. Here, discrepancies are likely controlled by temporal variability in ice discharge and other related processes not represented by our model simulations, i.e., hydrological processes and ice–ocean interaction. In the southeast, GRACE_JPL exhibits larger seasonal amplitude than predicted by the models while simultaneously having more pronounced trends; thus, discrepancies are likely controlled by a combination of missing processes and errors in both the SMB products and ISSM. At the margins, we find evidence of consistent intra-annual variations in regional MB that deviate distinctively from the SMB annual cycle. Ultimately, these monthly-scale variations, likely associated with hydrology or ice–ocean interaction, contribute to steeper negative mass trends observed by GRACE_JPL. Thus, models should consider such processes at relatively high (monthly-to-seasonal) temporal resolutions to achieve accurate estimates of Greenland MB. [less ▲]

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See detailApplication of groundwater models in karstic aquifers
Dassargues, Alain ULg

in Leibundgut, Christian; Gunn, John; Dassargues, Alain (Eds.) Karst Hydrology (Proc. of Rabat Workshop W2) (1998)

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See detailApplication of heparin as a dual agent with antimalarial and liposome targeting activities toward Plasmodium-infected red blood cells
Marques, J.; Moles, E.; Urbán, P. et al

in Nanomedicine (2014), 10(1719–1728),

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See detailApplication of High-Performance Liquid Chromatography to the Study of Thiamine Metabolism and in Particular Thiamine Triphosphatase
Bettendorff, Lucien ULg

in Journal of Chromatography. A (1991), 566(2), 397-408

Thiamine triphosphate can be found in most tissues at very low levels, but its role is unknown. Organs and muscles that generate electrical impulses are particularly rich in this compound. This paper ... [more ▼]

Thiamine triphosphate can be found in most tissues at very low levels, but its role is unknown. Organs and muscles that generate electrical impulses are particularly rich in this compound. This paper describes a thiamine triphosphatase from the electrical organ of Electrophorus electricus. The activity of this enzyme, as measured by a high-performance liquid chromatographic method, is closely anion-regulated. Furthermore, thiamine triphosphate increases chloride uptake in membrane vesicles prepared from rat brain. Our results suggest that this compound could play an important role in the regulation of chloride permeability. [less ▲]

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See detailApplication of Higher-Order Harmonic Balance to Non-Linear Aeroelastic Systems
Dimitriadis, Grigorios ULg; Vio, Gareth Arthur; Cooper, Jonathan Edward

in Proceedings of the 47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference (2006, May)

The influence of non-linearities on modern aircrafts is becoming of increasing impor- tance. The ability to accurately characterise LCOs and to predict at which speed they occur is very important. Higher ... [more ▼]

The influence of non-linearities on modern aircrafts is becoming of increasing impor- tance. The ability to accurately characterise LCOs and to predict at which speed they occur is very important. Higher Order Harmonic Balance (HOHB) methods have attracted some interest from the aeroelastic community over the last two decades. Such methods carry the promise of high quality stability prediction and Limit Cycle Oscillation (LCO) amplitude and frequency prediction for non-linear aeroelastic systems. In this paper, a Higher Order Harmonic Balance scheme is devised to extend the effectiveness of the method to systems undergoing secondary Hopf bifurcations. It is shown that the proposed harmonic shifting technique can allow the HOHB method to accurately estimate both branches of limit cycles occurring after the second bifurcation. [less ▲]

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See detailApplication of hyperspectral Raman imaging to the analysis of a self-emulsifying drug delivery system (SEDDS).
Sacre, Pierre-Yves ULg; De Bleye, Charlotte ULg; Netchacovitch, Lauranne ULg et al

Poster (2014, June)

Self-emulsifying drug delivery systems (SEDDS) are mixtures of drug and excipients that undergo emulsification when exposed to water. This pharmaceutical form is used to enhance the oral absorption of ... [more ▼]

Self-emulsifying drug delivery systems (SEDDS) are mixtures of drug and excipients that undergo emulsification when exposed to water. This pharmaceutical form is used to enhance the oral absorption of poorly water-soluble drugs. The API is finely dispersed in the excipients and forms a solid solution increasing its dissolution rate. Hyperspectral Raman imaging is a powerful tool that combines both spectral and spatial information. It returns qualitative and quantitative information useful during the development or the characterization of pharmaceutical preparations. The studied formulation consisted of a BCS 2 API (high permeability, low solubility) dispersed in excipients mainly composed of Lauroyl macrogol-32 glycerides (>50%). Two different preparations were analyzed: 100% of API dissolved and 70% of API dissolved with 30% of API powder added to the formulation. The two formulations have therefore exactly the same qualitative and quantitative composition but different spatial distribution and dispersion of the API mimicking a problem during the process. First a confocal Raman microscopic analysis was performed to evaluate the solid state of the API in the formulations. Then, an evaluation of the particle size was performed. These results are important since they can affect the bioavailability of the API and therefore its activity. Beside the microscopic scale analysis, a macroscopic imaging quantitative PLS model has been developed. The method has been validated within +/- 10% acceptance limits following the total error approach. This validated quantitative model enables reliable quantitative analysis at the pixel level of Raman images providing meaningful chemical images. [less ▲]

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See detailApplication of image analysis in food drying
Jinorose, Maturada; Devahastin, Sakamon; Blacher, Silvia ULg et al

in Ratti, C. (Ed.) Advances in Food Dehydration (2009)

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See detailApplication of image analysis to the identification and rating of road surface distress
Rasse, Catherine; Leemans, Vincent ULg; Destain, Marie-France ULg et al

in Correia; Branco (Eds.) Bearing Capacity of Roads, Railways and Airfields (2002)

Numerical image analysis is used to detect narrow cracks on bituminous pavement. This problem is complicated because of the variable road aspect, which depends on coarseness textures, changing ambient ... [more ▼]

Numerical image analysis is used to detect narrow cracks on bituminous pavement. This problem is complicated because of the variable road aspect, which depends on coarseness textures, changing ambient lighting, presence of humidity and because of the poor contrast of the cracks with regard to road texture. The paper presents algorithms suited to detect random cracks edges in a noisy environment in three stages. The pre-treatment consisted mainly in applying a background correction to eliminate the heterogeneity due to humidity, shade, ... In the treatment, a threshold value was applied to segment the 'object' from the rest of the image. As these objects may be cracks, part cracks, or some noise erroneously segmented as defect, a post-treatment was applied to appreciate more accurately if a pixel belonged to an object or to the background. It aimed also to assembly parts of the cracks in continuous structure. When compared to visual detection, efficient detection of cracks is obtained. Further work needs to be done to get an automatic detection of the cracks whatever the road texture. [less ▲]

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See detailApplication of ion beam techniques for cultural heritage knowledge and conservation
Aucouturier, M.; Bouquillon, A.; Chabanne, Dehlia et al

in Brai, Maria (Ed.) Tecniche di analisi di materiali nei Beni Culturali : volume degli atti del Workshop su: "Tecniche di analisi non distruttive di materiali lapidei naturali e artificiali nei Beni Culturali, Palermo 22 febbraio 2007 (2007)

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See detailApplication of isotopic tracers as a tool for understanding hydrodynamic behavior of the highly exploited Diass aquifer system (Senegal)
Madioune, Diakher Hélène; Faye, Serigne; Orban, Philippe ULg et al

in Journal of Hydrology (2014), 511

The Diass horst aquifer system located 50 km east of Dakar (Senegal) is exploited in two main aquifers covered by a sandy superficial aquifer: the confined/unconfined Palaeocene karstic limestone and the ... [more ▼]

The Diass horst aquifer system located 50 km east of Dakar (Senegal) is exploited in two main aquifers covered by a sandy superficial aquifer: the confined/unconfined Palaeocene karstic limestone and the confined Maastrichtian sandstone aquifer underneath. This system has experienced intensive groundwater abstraction during the last 50 years to supply increasing water demand, agricultural and industrial needs. The high abstraction rate from 1989 to 2009 (about 109,000 m3/d) has caused a continuous groundwater level decline (up to 30 m), a modification of the groundwater flow and salinization in parts of the aquifers. The objective of the study is to improve our understanding of the system functioning with regards to high pumping, identify the geochemical reactions that take place in the system, infer origin and timing of recharge by using mainly stable (δ18O, δ2H, 13C) and radioactive (3H and 14C) isotopes. Water types defined in the Piper diagram vary in order of abundance from Ca–HCO3 (65%), Ca/Na–Cl (20%), Na–HCO3 (3%) and Na–Cl (12%). Values of δ18O and δ2H for the superficial aquifer range between −5.8 and −4.2‰ and between −42 and −31‰, respectively. For the Palaeocene aquifer they range from −5.8 to −5.0‰ and from −38 to −31‰, respectively; values in the Maastrichtian aquifer are between −5.9 and −4.3‰ for δ18O and −38 to −26‰ for δ2H. Plotted against the conventional δ18O vs δ2H diagram, data from the upper aquifer exhibit a dispersed distribution with respect to isotopic fractionation while those of the Palaeocene and Maastrichtian aquifers are aligned parallel and slightly below/or on the Global Meteoric Water Line (GMWL) evidencing ancient waters which had evaporated during infiltration. The low tritium (generally <0.7 TU) and 14C (0.7–57.2 pmc) contents indicate predominance of older water being recharged during the Pleistocene and Holocene periods. However, few boreholes which exhibit high tritium (1.2–4.3 TU) and 14C (65.7–70.8 pmc) values indicate some mixture with recent water likely through faulting and vertical drainage from the upper to deeper aquifers as well as lateral flow along flow paths to the piezometric depressions created by pumping. [less ▲]

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See detailApplication of Laser Induced Breakdown Spectroscopy (LIBS) to the determination of transition probabilities of laser lines in Au II spectrum
Ortiz, M.; Mayo, R.; Biémont, Emile ULg et al

Conference (2007)

Experimental branching fractions for laser lines arising from excited states of 5d97s configuration of Au II have been determined by application of Laser Induced Breakdown Spectroscopy (LIBS). The ... [more ▼]

Experimental branching fractions for laser lines arising from excited states of 5d97s configuration of Au II have been determined by application of Laser Induced Breakdown Spectroscopy (LIBS). The experimental relative transition probabilities were converted into an absolute scale using theoretical values for the radiative lifetimes of the corresponding states, calculated in this work. Transition probabilities and radiative lifetimes have been determined by a relativistic Hartree - Fock method taking configuration interaction and core-polarization effects into account. A comparison of the present results with the available theoretical values has been made and shows a reasonable agreement although discrepancies are observed between theory and experiment for some transitions. [less ▲]

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See detailApplication of lasso penalization to differential item functioning detection
Magis, David ULg

Scientific conference (2013, February 26)

Identification of differential item functioning (DIF) in dichotomously scored items is often performed item by item. This approach increases the risk of false discovery errors (Type I error rate) as all ... [more ▼]

Identification of differential item functioning (DIF) in dichotomously scored items is often performed item by item. This approach increases the risk of false discovery errors (Type I error rate) as all items other than the tested one are assumed to be free of DIF. Some ad-hoc procedures, such as item purification and alpha level adjustment for multiple comparisons, have been studied in this context. The purpose of this talk is to focus on a different approach based on penalized likelihood estimation of a look-alike IRT model. Specifically, a Rasch model is being introduced with item-group interaction terms (i.e. DIF effects). Rather than obtaining pointwise estimates of the interaction parameters, which may be impossible because of high collinearity effects, the DIF effects are estimated with a lasso penalty term. Several criteria for optimally selecting the lasso tuning parameter are discussed, including cross-validation, AIC, BIC, and variants of these criteria. Preliminary results of a simulation study are presented and discussed. [less ▲]

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