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See detailContribution to the specialist committee V.3 entitled "Fabrication Technology" of the 16th International Ship and Offshore Structure Congress
Caprace, Jean-David ULg

in Borzecki, T.; Bruce, G.; Han, Y. S. (Eds.) et al Specialist committee V.3 - Fabrication technology (2008, August)

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See detailContribution to the statistical evaluation of data obtained in External Quality Assessment programmes
Coucke, Wim ULg

Doctoral thesis (2012)

Laboratory medicine has undergone a spectacular evolution in the last decades and has become today of crucial importance for supporting diagnostic and therapeutic decisions. The increase of the volume of ... [more ▼]

Laboratory medicine has undergone a spectacular evolution in the last decades and has become today of crucial importance for supporting diagnostic and therapeutic decisions. The increase of the volume of laboratory analyses has not gone without an emerging risk of measurement errors that may have far-reaching consequences, even on the patient’s life. External Quality Assessment (EQA), already established since several decades in various countries and often running on an international level, aim at going further than the "internal quality control" procedures of every laboratory and at improving laboratory quality by inter-laboratory comparisons. An EQA round generally consists of sending aliquots of the same sample to various laboratories for assaying selected tests. After finishing the assays, results are reported back to the EQA organizer. Subsequently these results are subject to a statistical analysis, which is performed globally, for all the participants, or for each analytical technique separately. Finally, a report is sent to every participant that informs about the acceptability of the individual results, with respect to predefined limits, and with respect to the group of peers. This thesis, structured in five chapters, focuses on the External Quality Control of clinical laboratories by a critical analysis of existing methods and by creating new approaches that permit to improve the current procedures. The first chapter of this work emphasizes the evolution of the role of the clinical laboratory and EQA in the quality improvement. After the report ’To Err is Human: Building a Safer Health System’, numerous scientists became interested in investigating the frequency, source and impact of laboratory errors. The Total Testing Process (TTP) became recognized as the best framework to investigate laboratory errors. The three different phases of the TTP - respectively, the pre-analytical, analytical and post-analytical phases - are described in detail and the nature and frequency of errors in each phase explained. For each phase, possible improvements are described and the role of EQA is suggested. Today, EQA principally focuses on the assessment and improvement of the analytical phase. Proposals are made to improve the role of EQA for assessing and improving pre- and post-analytical error as well, by using specific sample material and by automating the reporting of data and laboratory reports to the EQA participants. The principle of the comparison of results of a laboratory with those obtained by the other laboratories is traditionally based on the calculation of "z-scores". An indepth study comparing different techniques has been made, shedding new light on the shortcomings and strong points of the different approaches. We concluded that robust techniques may exhibit weak performance for smaller sample size, while techniques that eliminate outliers before calculating zscores should be recommended. The second Chapter discusses the role of EQA as a tool to assess harmonization between methods. The role of EQA is described, together with the pitfalls and current shortcomings for assessing harmonization. A major problem in assessing standardization between methods is the possible presence of matrix effects in control samples, in which a method-specific bias may appear. Several explanations for matrix effects are mentioned and statistical techniques are described that assist EQA organizers to split up the data in homogeneous peer groups using multivariate statistics. The chapter also reviews several techniques to be used in method comparison studies, and the preference for the use of orthogonal regression is expressed. In addition, an example is given of a method-comparison study for Estradiol and Progesterone, with a novel technique of assessing standardization between various methods, in the presence of matrix effects for a small number of samples. The study also reveals that standardization between various methods is not attained, and that the striving for standardization with standards of higher order may not be satisfactory. Chapter 3 introduces different evaluation techniques that combine information from different samples or parameters: Variance and bias index scores, Mean ranking scores, counts of z- and u-scores, and a long-term analytical Coefficient of Variation. Also, a new and original method is introduced that uses 3 steps to identify outliers in a first step, to find laboratories with exceeding variability in a second, and to identify laboratories with high bias in a third step. Each of the techniques are evaluated and discussed by means of a data set in which accidental outliers, high variability and high bias were induced. In addition, the comparison between the different evaluation methods reveals that distinguishing between variability and bias is a tedious task, and that some long-term analysis methods lack robustness against outliers. Also, it is proven that evaluation techniques summarizing results of different parameters may hide useful information. In addition, the 3-step method is proposed as a method for discerning between errors produced in the pre- or post-analytical phase, and errors that arise from the analytical phase. Chapter 4 applies the 3-step method to data obtained from the Belgian EQA. Data sets from alcohol, flow cytometry, lithium and semen analysis surveys are examined. The method is extended for applicability to heteroscedastic, i.e. unequal residual variability, regression models and demonstrates that it is able to be used in a wide range of surveys. For each of the surveys under consideration, a follow-up is made of the occurrence of accidental mistakes, and the evolution of within-laboratory variability and bias for selected methods. It highlights several conclusions that show a striking similarity for various EQA surveys: an improvement of laboratory performance has been attained over time. The major improvement was a reduction of accidental mistakes. The analytical performance of selected methods, however, did not show an improvement over time. In Chapter 5, some graphical representations of EQA data are explored and a graphical representation of the 3-step method is described. The histogram, normal quantile plot and box plot are described in detail and suggested for providing a quick visual overview of EQA data. Other graphical representations that respond to specific questions are given and discussed as well, like Shewhart charts, Cusum charts and graphical representations to combine variability and bias in one graph. In addition, the 3-step method is graphically explored by means of three distinct graphs. The chapter finishes by suggesting the use of interactive graphs for improving feedback from the EQA organizers to the EQA participants by means of Scalable Vector Graphics. The latter is illustrated with web-accessible examples of long-term evaluation of z-scores and the results of the 3-step method for the data obtained in the Belgian EQA for alcohol determination in blood. In brief, this work describes in a critical and constructive way current statistical methods used in EQA and proposes novel statistical and graphical techniques to help alleviating the future needs of External Quality Assessment programmes. [less ▲]

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See detailContribution to the study of acoustic communication in two Belgian river bullheads (Cottus rhenanus and C. perifretum) with further insight into the sound-producing mechanism
Colleye, Orphal ULg; Ovidio, Michaël ULg; Salmon, André et al

in Frontiers in Zoology (2013), 10(71),

Background: The freshwater sculpins (genus Cottus) are small, bottom-living fishes widely distributed in North America and Europe. The taxonomy of European species has remained unresolved for a long time ... [more ▼]

Background: The freshwater sculpins (genus Cottus) are small, bottom-living fishes widely distributed in North America and Europe. The taxonomy of European species has remained unresolved for a long time due to the overlap of morphological characters. Sound production has already been documented in some cottid representatives, with sounds being involved in courtship and agonistic interactions. Although the movements associated with sound production have been observed, the underlying mechanism remains incomplete. Here, we focus on two closely related species from Belgium: C. rhenanus and C. perifretum. This study aims 1) to record and to compare acoustic communication in both species, 2) to give further insight into the sound-producing mechanism and 3) to look for new morphological traits allowing species differentiation. Results: Both Cottus species produce multiple-pulsed agonistic sounds using a similar acoustic pattern: the first interpulse duration is always longer, making the first pulse unit distinct from the others. Recording sound production and hearing abilities showed a clear relationship between the sound spectra and auditory thresholds in both species: the peak frequencies of calls are around 150 Hz, which corresponds to their best hearing sensitivity. However, it appears that these fishes could not hear acoustic signals produced by conspecifics in their noisy habitat considering their hearing threshold expressed as sound pressure (~ 125 dB re 1 ␣Pa). High-speed video recordings highlighted that each sound is produced during a complete back and forth movement of the pectoral girdle. Conclusions: Both Cottus species use an acoustic pattern that remained conserved during species diversification. Surprisingly, calls do not seem to have a communicative function. On the other hand, fish could detect substrate vibrations resulting from movements carried out during sound production. Similarities in temporal and spectral characteristics also suggest that both species share a common sound-producing mechanism, likely based on pectoral girdle vibrations. From a morphological point of view, only the shape of the spinelike scales covering the body allows species differentiation. [less ▲]

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See detailContribution to the study of Alchornea cordifolia (Schumach. & Thonn.)
Mavar-Manga, H; Brkic, D; De Pauw-Gillet, Marie-Claire ULg et al

Conference (2002, March)

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See detailContribution to the study of alliinase, the active principle of garlic
DETHIER, Bérénice ULg; Ponchaux, Julien; Laloux, Morgan et al

Poster (2014, February 07)

Alliinase is a crucial enzyme in the Allium genus. The conversion of its substrates, cysteine sulfoxides, into volatile thiosulfinates is an important mechanism in the defence of the plant. It also ... [more ▼]

Alliinase is a crucial enzyme in the Allium genus. The conversion of its substrates, cysteine sulfoxides, into volatile thiosulfinates is an important mechanism in the defence of the plant. It also provides the typical pungent flavour of garlic. As a matter of fact, the thiosulfinates decompose in a range of organosulfur compounds (OSC) known for their biological activities (antioxidant, anticancer, anti-diabetes properties, etc.). The environment of the decomposition of the thiosulfinates determines the type and amount of products released. A deeper knowledge of the conditions that form each OSC could help us in the preparation of garlic-based nutraceutics in the perspective of healthier food consumption. This study aims to improve the extraction and purification the enzyme alliinase in order to perform the reaction between the enzyme and its substrates and assess the potentialities of garlic preparations. Three methods have been applied to evaluate the efficiency of the extractions and purifications of the enzyme. A first idea of the purity of the enzyme is given by an electrophoresis separation of each sample on a polyacrylamide gel (SDS-PAGE). The protein content is then measured by UV-vis spectrometry with Lowry-Folin reagent for the coloration and BSA as an external standard. Finally, the specific activity is assessed by an indirect measure of the pyruvate (released as a co-product): the addition of NADH and lactate dehydrogenase turns the pyruvate in lactate, and the disappearance of NADH is measured by UV-vis spectrometry at 340 nm. The extraction of the enzyme from garlic was performed either by PEG 8000 precipitation or by ammonium sulphate precipitation. Two purifications were tested: affinity chromatography (on ConA) and size-exclusion chromatography. The combination of the ammonium sulphate process with the ConA chromatography provided the purest enzyme, with the best activity but a lower yield than the size-exclusion process. Finally the stability of the enzyme has been assessed at 4, -20 and -80 °C, showing that the enzyme could be kept at -80 °C for over 4 months without deterioration, while activity loss was observed at higher temperature. [less ▲]

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See detailContribution to the study of camel milk fat globule membrane
Karray, Nadia Laadhar; Danthine, Sabine ULg; Blecker, Christophe ULg et al

in International Journal of Food Sciences & Nutrition (2006), 57(5-6), 382-390

The camel milk fat globule membrane has been characterized according to several approaches. Compared with the cow milk fat globule membrane, various specificities have been revealed. Its physicochemical ... [more ▼]

The camel milk fat globule membrane has been characterized according to several approaches. Compared with the cow milk fat globule membrane, various specificities have been revealed. Its physicochemical composition showed a poor content in proteins, and a higher content in neutral lipids and in phospholipids. The mechanical properties measured at low (4 degrees C, 20 degrees C) and high temperatures (40 degrees C, 45 degrees C and 50 degrees C) using a film balance are different when the camel milk fat globule membrane is spread at the air-water interface. The thermal study revealed an important proportion of high-melting triacylglycerols that involves fatty acids with long chains. [less ▲]

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See detailContribution to the study of physicochemical and functional properties of hemicelluloses and xylooligosaccharides (XOS) extracted from rapeseed meal
Mertens, Cécile ULg; Paquot, Michel ULg; Destain, Jacqueline ULg et al

Poster (2012, February 08)

Rapeseed meal is one of the main industrial co-products from agriculture in Belgium, with more than 30 000 T produced each year. Beside its agricultural and energetic applications, new paths of ... [more ▼]

Rapeseed meal is one of the main industrial co-products from agriculture in Belgium, with more than 30 000 T produced each year. Beside its agricultural and energetic applications, new paths of valorization are being developed in order to add value to the rapeseed meal, usually by extraction of interesting molecules. In this thesis project, the aimed molecules are hemicelluloses, which are obtained via a global fractionation method that is being developed and optimized, constituting the first part of this project. Indeed, while rapeseed meals are globally already well exploited (mainly for their feed value), rapeseed hemicelluloses have not yet been studied for food application. Yet, hemicelluloses can be used as food additives (thickener, stabilizer, etc) mainly in bakery products. The literature being incomplete regarding the chemical structure of rapeseed hemicelluloses, one of the objectives of this project is to study their physicochemical properties, in regard with their technofunctional properties. Rapeseed hemicelluloses can also be used as raw material to produce an emergent type of prebiotic: xylooligosaccharides (XOS). These molecules can be introduced as well in the food supplement sector. Their production will be achieved by enzymatic hydrolysis, for a polymerization degree between two and five. Thus, the production and the physicochemical and technofunctional characterization of rapeseed XOS constitute the last objective of this project. This thesis is part of the SYNBIOFOR project, which aim is to create new symbiotic ingredients. [less ▲]

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See detailContribution to the study of piano Key Weir hydraulics
Erpicum, Sébastien ULg; Machiels, Olivier ULg; Dewals, Benjamin ULg et al

in Proceedings of the 8th ICOLD European Club Symposium (2010)

Within the framework of updating the release and storage capacities of existing reservoirs, the use of piano key weirs (PKW) can be an interesting alternative either to increase the discharge of a free ... [more ▼]

Within the framework of updating the release and storage capacities of existing reservoirs, the use of piano key weirs (PKW) can be an interesting alternative either to increase the discharge of a free weir without changing the weir width on the dam crest nor the reservoir level, or to increase the threshold reservoir level before releasing water while keeping the weir width and the level of safety. Results of first experiments on scale models have shown the high efficiency of PKW in terms of discharge capacity. But, even if PKW projects start to be developed on real structures, lacks persist in the understanding of the flow behavior on this new type of weir, in the characterization of their hydraulic potential and in the availability of design guidelines. This paper presents the results of several research projects, based on both numerical and physical modeling, carried out on this topic at the Laboratory of Engineering Hydraulics of the University of Liege. The researches rely on physical experiments on scale models of idealized PKW elements or real structures, as well as on numerical modeling with specifically developed solvers. The paper presents an overview of these projects, emphasizing the most important results regarding PKW design and performance. [less ▲]

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See detailContribution to the study of semiochemical slow release formulations. Development of flash chromatographic methods.
Heuskin, Stéphanie ULg; Farmakidis, Julien; Lorge, Stéphanie et al

Poster (2009)

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See detailContribution to the study of semiochemical slow-release formulations as biological control devices
Heuskin, Stéphanie ULg

Doctoral thesis (2011)

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been widely considered within various integrated pest management (IPM) strategies. In the present thesis ... [more ▼]

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been widely considered within various integrated pest management (IPM) strategies. In the present thesis, two sesquiterpenoids, E-β-farnesene and E-β-caryophyllene, were formulated for their related properties as aphid enemy attractants. E-β-farnesene, the alarm pheromone of many aphid species, was also identified as a kairomone by attracting and inducing oviposition of aphid predators (Episyrphus balteatus De Geer (Diptera: Syrphidae)) and by attracting aphid parasitoids (Aphidius ervi Haliday (Hymenoptera: Braconidae)). E-β-caryophyllene was identified as a potential component of the aggregation pheromone of the Asian ladybird, Harmonia axyridis Pallas, another aphid predator. The two products were purified from essential oils of Matricaria chamomilla L. (Asteraceae) and Nepeta cataria L. (Lamiaceae) for E-β-farnesene and E-β-caryophyllene, respectively. Natural and biodegradable slow-release formulations were then investigated in order to deliver these molecules on crop fields for a long period of time as biological control devices. Due to their sensitivity to oxidation, both sesquiterpenes needed to be protected from oxygen degradation. For this purpose, alginate – hydrophilic matrix with low oxygen permeability – was used as polymer for the formulations: the main objective was to deliver semiochemical substances in the air in a controlled way. Consequently, a careful selection of alginates was realised. Formulated beads showed different structural and encapsulation properties depending on various formulation factors. Alginate formulations were characterized by texturometry and by confocal microscopy in order to observe the distribution of semiochemicals in alginate network. The last step of alginate bead characterisation consisted in studying release rate of semiochemicals in laboratory-controlled conditions by optimised trapping and validated Fast-GC procedures. Finally, the efficiency of formulations as aphid predator (Syrphidae) and parasitoids (A. ervi) attractants was demonstrated by field trapping and olfactometry experiments. [less ▲]

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See detailContribution to the study of stress cracking phenomenon by oxidative induction time measurements
Rigo, Jean-Marie ULg; Courard, Luc ULg; Detaille, Laurence et al

in Delmas, Philippe; Gourc, Jean-Pierre (Eds.) Proceedings of the Rencontres 95 (1995)

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See detailContribution to the study of Strychnos usambarensis GILG, main ingredient of an African curarizing arrow poison
Angenot, Luc ULg

in Dissertation Abstracts (1974), 34(11), 338

The thesis is subdivided in four parts and two annexes . the first part concerns the choice of Strychnos usambarensis based on ethnobotanical considerations; the second part is dedicated to the study of ... [more ▼]

The thesis is subdivided in four parts and two annexes . the first part concerns the choice of Strychnos usambarensis based on ethnobotanical considerations; the second part is dedicated to the study of arrow poisons in the World and particularly in Africa; the third part describes the isolation of eight indole alkaoids ( 5 new and 3 known ones) and their structure determination thanks to modern spectroscopic methods.The fourth part is applied to the biosynthesis of these alkaloids and to the identification of loganic acid.The first appendix describes the phytochemical screening of 33 Rwandan plants mainly collected in the National Park of Akagera. The second appendix relates pharmacological experiments on crude fractions and some isolated alkaloids. [less ▲]

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See detailContribution to the study of the allosteric properties of acetylcholinesterase
Gridelet, J.; Foidart, Jean-Michel ULg; Wins, P.

in Archives Internationales de Physiologie et de Biochimie (1970), 78

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