Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
See detailThe combination of illuminants and its effect on colour rendering
Embrechts, Jean-Jacques ULg

in Proceedings of the Colour Dynamics '88 Congress (1988)

Detailed reference viewed: 15 (3 ULg)
Full Text
Peer Reviewed
See detailCOMBINATION OF INDEPENDENT COMPONENT ANALYSIS, DESIGN OF EXPERIMENTS AND DESIGN SPACE FOR A NOVEL METHODOLOGY TO DEVELOP CHROMATOGRAPHIC METHODS
Rozet, Eric ULg; Debrus, Benjamin ULg; Lebrun, Pierre ULg et al

Poster (2012, February)

As defined by ICH [1] and FDA, Quality by Design (QbD) stands for “a systematic approach to development that begins with predefined objectives and emphasizes product and process understanding and process ... [more ▼]

As defined by ICH [1] and FDA, Quality by Design (QbD) stands for “a systematic approach to development that begins with predefined objectives and emphasizes product and process understanding and process control, based on sound science and quality risk management”. A risk–based QbD–compliant approach is proposed for the robust development of analytical methods. This methodology based on Design of Experiments (DoE) to study the experimental domain models the retention times at the beginning, the apex and the end of each peak corresponding to the compounds of a mixture and uses the separation criterion (S) rather than the resolution (RS) as a Critical Quality Attribute. Stepwise multiple linear regressions are used to create the models. The estimated error is propagated from the modelled responses to the separation criterion (S) using Monte Carlo simulations in order to estimate the predictive distribution of the separation criterion (S) over the whole experimental domain. This allows finding ranges of operating conditions that will guarantee a satisfactory quality of the method in its future use. These ranges define the Design Space (DS) of the method. In chromatographic terms, the chromatograms processed at operating conditions within the DS will assuredly show high quality, with well separated peaks and short run time, for instance. This Design Space can thus be defined as the subspace, necessarily encompassed in the experimental domain (i.e. the knowledge space), within which the probability for the criterion to be higher than an advisedly selected threshold is higher than a minimum quality level. Precisely, the DS is defined as “the multidimensional combination and interaction of input variables (e.g., material attributes) and process parameters that have been demonstrated to provide assurance of quality” [1]. Therefore, this DS defines a region of operating conditions that provide prediction of assurance of quality rather than only quality as obtained with traditional mean response surface optimisation strategies. For instance, in the liquid chromatography there is a great difference in e.g. predicting a resolution (RS) higher than 1.5 vs. predicting that the probability for RS to be higher than 1.5 (i.e. P(RS> 1.5)) is high. The presentation of this global methodology will be illustrated for the robust optimisation and DS definition of several liquid chromatographic methods dedicated to the separation of different mixtures: pharmaceutical formulations, API and impurities/degradation products, plant extracts, separation of enantiomers, … References [1] International Conference on Harmonisation (ICH) of Technical Requirements for Registration of Pharmaceuticals for Human Use, Topic Q8(R2): Pharmaceutical development, Geneva, 2009. [less ▲]

Detailed reference viewed: 141 (9 ULg)
Full Text
See detailCombination of lipase catalysis and thiol-Michael addition for the synthesis of carbohydrate esters used as stabilizers in supercritical carbon dioxide emulsions
Boyère, Cédric ULg; Favrelle, Audrey; Broze, Guy ULg et al

Poster (2011, November 21)

The use of aqueous dispersed media, such as emulsions and miniemulsions, has many advantages over solution processes for chemical transformations and polymerization reactions, i.e. limited environmental ... [more ▼]

The use of aqueous dispersed media, such as emulsions and miniemulsions, has many advantages over solution processes for chemical transformations and polymerization reactions, i.e. limited environmental impact, ease of products recovery and increased reaction rate. Although, dispersed media are usually implemented from water/solvent mixtures, supercritical carbon dioxide (scCO2) (Pc =74 bars; Tc = 31°C) constitutes an interesting alternative to the traditional organic solvents because it is inexpensive, non-toxic, non-flammable and environmentally friendlier. In this context, we develop a novel class of surface active compounds able to stabilize water/scCO2 emulsions, i.e. fluorinated modified carbohydrates. The hydrophilic head of the surfactant consists in a sugar moiety whereas the fluorinated tail has a strong affinity for the scCO2 phase. These carbohydrate esters are prepared by a two-step strategy which takes advantage of the selectivity of enzymatic catalysis and the versatility of the thiol-Michael addition reaction. The new thiolated mannose intermediate is a useful building block for the incorporation of unprotected sugar moieties into complex molecules. The surface active properties of the fluorinated derivatives have been evaluated as well as their use as stabilizers for the preparation of microparticles and highly porous polymer materials in scCO2. [less ▲]

Detailed reference viewed: 55 (5 ULg)
Full Text
Peer Reviewed
See detailCombination of mechanical and optical profilometry techniques for concrete surface roughness characterization
Perez, Fabien; Bissonnette, Benoît; Courard, Luc ULg

in Magazine of Concrete Research (2009), 61(6)

Achieving durable bond between new and old concrete still represents a challenge in concrete repair technology. It has been the subject of a number of investigations, but in most cases, only adhesion ... [more ▼]

Achieving durable bond between new and old concrete still represents a challenge in concrete repair technology. It has been the subject of a number of investigations, but in most cases, only adhesion strength was addressed. To better understand bond mechanisms, in particular those related to surface roughness, two complementary surface characterisation techniques were implemented, providing a multiscale roughness characterisation by means of specific filtering calculations: mechanical profilometry for low-scale roughness and optical profilometry for the upscale roughness. Using these complementary approaches, different types of concrete surface preparation were characterised. The resulting description highlights the complexity of concrete surface topography. Moreover, it shows that the type of surface preparation essentially affects the meso- and macro-roughness levels, microroughness being practically insensitive. Such results will be useful for better understanding the interlocking potential and bond performance of concrete repairs. [less ▲]

Detailed reference viewed: 71 (0 ULg)
Peer Reviewed
See detailCombination of oral antidiabetic drugs and insulin in the treatment of non-insulin-dependent diabetes.
Scheen, André ULg; Castillo, M. J.; Lefebvre, Pierre ULg

in Acta Clinica Belgica (1993), 48(4), 259-68

Non-insulin-dependent diabetes mellitus (NIDDM) appears to be an heterogeneous disorder characterized by both relative insulin deficiency and impaired insulin action. The initial management of NIDDM ... [more ▼]

Non-insulin-dependent diabetes mellitus (NIDDM) appears to be an heterogeneous disorder characterized by both relative insulin deficiency and impaired insulin action. The initial management of NIDDM should include patient education, dietary counselling and individualized programs of physical activity. It is only when such measures fail that drug therapy should be considered. Oral drug therapies include sulphonylurea derivatives, biguanides, among which metformin remains the only one commercialized in our country, and alpha-glucosidase inhibitors such as acarbose. However, insulin therapy may be required to achieve adequate glycaemic control in some patients, the so-called secondary failures to oral treatment. The rationale for combining insulin and oral drug therapy derives from a better understanding of the pathophysiology of NIDDM and of the mechanisms of action of the oral drugs available: 1) type 2 diabetic patients are both insulin-deficient and insulin-resistant, thus requiring quite high doses of exogenous insulin; 2) peripheral insulin delivery leads to hyperinsulinaemia which could play a role in the pathogenesis of late diabetic complications; 3) sulphonylureas stimulate insulin release directly into the portal vein and could also potentiate peripheral insulin action; and 4) metformin (by improving glucose metabolism and insulin sensitivity) and alpha-glucosidase inhibitors (by slowing down the digestion of complex carbohydrates and sucrose) are able to reduce the amounts of insulin needed to control postprandial hyperglycaemia. Numerous studies have shown that a combination of insulin and sulphonylurea is more effective than insulin alone in the treatment of patients with NIDDM after secondary failure to oral drugs, leading to better glucose profiles and/or decreased insulin needs. The available data suggest that combination therapy is most beneficial in the diabetic patient who still has residual insulin secretory capacity and that the best scheme comprises an evening injection of lente insulin and the administration of sulphonylureas before meals. Preliminary results suggested that insulin-metformin (when obesity is present) or insulin-acarbose (when post-prandial hyperglycaemia occurs) combinations might offer some favourable features for the treatment of NIDDM patients although these therapeutical approaches still require adequate evaluation in further controlled studies. The additional cost of such combined therapy should be weighed against the potential advantages of better metabolic control. [less ▲]

Detailed reference viewed: 29 (0 ULg)
Full Text
Peer Reviewed
See detailCombination of ring-opening polymerization and "click chemistry": Toward functionalization and grafting of poly(epsilon-caprolactone)
Riva, Raphaël ULg; Schmeits, Stéphanie; Jérôme, Christine ULg et al

in Macromolecules (2007), 40(4), 796-803

A straightforward strategy is proposed for the derivatization of poly(epsilon-caprolactone) (PCL). First, statistical copolymerization of alpha-chloro-epsilon-caprolactone (alpha-Cl-epsilon-CL) with ... [more ▼]

A straightforward strategy is proposed for the derivatization of poly(epsilon-caprolactone) (PCL). First, statistical copolymerization of alpha-chloro-epsilon-caprolactone (alpha-Cl-epsilon-CL) with epsilon-caprolactone (epsilon-CL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP). In a second step, pendent chlorides were converted into azides by reaction with sodium azide. Finally, duly substituted terminal alkynes were reacted with pendent azides by copper-catalyzed Huisgen's 1,3-dipolar cycloaddition, thus a "click" reaction. According to this strategy, pendent hydroxyl and acrylate groups and atom transfer radical polymerization (ATRP) initiators were successfully attached to PCL. Similarly, amphiphilic graft copolymers were prepared by cycloaddition of an alkyne end-capped poly(ethylene oxide) (PEO) onto the azide substituents of the copolyester. The dependence of the grafting yield on the experimental conditions of the "click" reaction, i.e., temperature, solvent, and catalyst, was investigated. This strategy is very versatile because a large variety of aliphatic polyesters can be easily synthesized from a single precursor, easily prepared from commercially available compounds, merely by changing the alkyne involved in the Huisgen's 1,3-dipolar cycloaddition. Last but not least, PCL subsituted by azide groups does not have to be isolated after substitution of chlorides by sodium azide, and the "click" reaction can be carried out in a "one-pot" process. [less ▲]

Detailed reference viewed: 107 (27 ULg)
Full Text
Peer Reviewed
See detailCombination of ring-opening polymerization and "click" chemistry for the synthesis of an amphiphilic tadpole-shaped poly(epsilon-caprolactone) grafted by PEO
Li, Haiying; Riva, Raphaël ULg; Jérôme, Robert ULg et al

in Macromolecules (2007), 40(4), 824-831

A tadpole shaped poly(epsilon-caprolactone) (PCL; Mn = 24 500) was made amphiphilic by grafting the two PCL tails with PEO. In the first step, a macrocyclic PCL was synthesized by ring-opening ... [more ▼]

A tadpole shaped poly(epsilon-caprolactone) (PCL; Mn = 24 500) was made amphiphilic by grafting the two PCL tails with PEO. In the first step, a macrocyclic PCL was synthesized by ring-opening polymerization of epsilon-caprolactone (epsilon-CL) initiated by a cyclic tin(IV) dialkoxide and stabilized by local intramolecular photo-cross-linking. In the second step, the polymerization of a mixture of epsilon CL and alpha-chloro-epsilon-caprolactone (alpha Cl epsilon CL) was resumed with formation of two activated chloride containing PCL tails. In the third step, the chlorides were converted into azides onto which alkynyl end-capped PEO was grafted by the copper-mediated Huisgen's cycloaddition [3 + 2], thus giving a "click" reaction. The thermal properties of the final copolymer and the precursors were analyzed by differential scanning calorimetry. The amphiphilicity of the final copolymer was confirmed by micellization in water. [less ▲]

Detailed reference viewed: 81 (18 ULg)
Full Text
Peer Reviewed
See detailCombination of ring-opening polymerization and "click" chemistry towards functionalization of aliphatic polyesters
Riva, Raphaël ULg; Schmeits, Stephanie ULg; Stoffelbach, François et al

in Chemical Communications (2005), (42), 5334-5336

Azide pendent groups of aliphatic polyesters have been derivatized into tertiary amines, ammonium salts and poly(ethylene oxide) grafts. The experimental conditions have been optimized (organic solvent ... [more ▼]

Azide pendent groups of aliphatic polyesters have been derivatized into tertiary amines, ammonium salts and poly(ethylene oxide) grafts. The experimental conditions have been optimized (organic solvent, 35 degrees C), such that the aliphatic polyesters are not degraded, including even poly(lactide) which is very sensitive to attack by weak nucleophiles. [less ▲]

Detailed reference viewed: 56 (13 ULg)
Peer Reviewed
See detailCombination of trophic biomarkers to distinguish among Antarctic amphipods trophic guilds
Nyssen, Fabienne ULg; Dauby, Patrick ULg; Graeve, Martin

Conference (2004, July)

Peracarid crustaceans and amphipods in particular are an important group in the Southern Ocean and one of the most diverse in the macrozoobenthos. As a part of a multidisciplinary study of the amphipods ... [more ▼]

Peracarid crustaceans and amphipods in particular are an important group in the Southern Ocean and one of the most diverse in the macrozoobenthos. As a part of a multidisciplinary study of the amphipods ecological roles in Antarctic benthic systems, about 150 specimens belonging to 25 species of 10 of the most common amphipod families occurring in the Southern Ocean have been involved in this study of amphipod trophic patterns. Beside “classical” stomach content analysis or field observations, the use of naturally occurring stable isotopes of carbon (δ13C) and nitrogen (δ15N) has recently provided new insights into food web ecology. This method is based on the direct relationship established between the isotopic signature of an organism and that of its preys. Nitrogen-15 typically shows a step-wise increase with trophic level within a food chain. Closer to the value of the diet, carbon-13 is preferentially used to assess the relative proportion of potential primary sources in a trophic web (ex.: pelagic vs benthic contribution to food intake). Furthermore, for several species, the lipid signature – which has already been used successfully to help understand marine trophodynamics – and more particularly the fatty acid composition has been investigated as trophic biomarkers to reveal more precisely to which trophic guild they belong to. [less ▲]

Detailed reference viewed: 23 (2 ULg)
Full Text
Peer Reviewed
See detailCombination therapy versus monotherapy: a randomised pilot study on the evolution of inflammatory parameters after ventilator associated pneumonia
Damas, Pierre ULg; Garweg, Christophe ULg; Monchi, Mehran et al

in Critical Care (2006), 10(2), 52

Introduction Combination antibiotic therapy for ventilator associated pneumonia (VAP) is often used to broaden the spectrum of activity of empirical treatment. The relevance of such synergy is commonly ... [more ▼]

Introduction Combination antibiotic therapy for ventilator associated pneumonia (VAP) is often used to broaden the spectrum of activity of empirical treatment. The relevance of such synergy is commonly supposed but poorly supported. The aim of the present study was to compare the clinical outcome and the course of biological variables in patients treated for a VAP, using a monotherapy with a beta-lactam versus a combination therapy. Methods Patients with VAP were prospectively randomised to receive either cefepime alone or cefepime in association with amikacin or levofloxacin. Clinical and inflammatory parameters were measured on the day of inclusion and thereafter. Results Seventy-four mechanically ventilated patients meeting clinical criteria for VAP were enrolled in the study. VAP was microbiologically confirmed in 59 patients (84%). Patients were randomised to receive cefepime (C group, 20 patients), cefepime with amikacin (C-A group, 19 patients) or cefepime with levofloxacin (C-L group, 20 patients). No significant difference was observed regarding the time course of temperature, leukocytosis or C-reactive protein level. There were no differences between length of stay in the intensive care unit after infection, nor in ventilator free days within 28 days after infection. No difference in mortality was observed. Conclusion Antibiotic combination using a fourth generation cephalosporin with either an aminoside or a fluoroquinolone is not associated with a clinical or biological benefit when compared to cephalosporin monotherapy against common susceptible pathogens causing VAP. [less ▲]

Detailed reference viewed: 13 (2 ULg)
Full Text
Peer Reviewed
See detailCombination/Sequential Therapy in Osteoporosis
Lecart, Marie-Paule; Bruyère, Olivier ULg; Reginster, Jean-Yves ULg

in Current Osteoporosis Reports (2004), 2(4), 123-30

Combination therapy includes the concomitant or sequential use of compounds sharing the same mode of action (eg, two or more inhibitors of bone resorption) or with distinct pathways of activity (eg, an ... [more ▼]

Combination therapy includes the concomitant or sequential use of compounds sharing the same mode of action (eg, two or more inhibitors of bone resorption) or with distinct pathways of activity (eg, an inhibitor of resorption plus an anabolic agent). Combination use of antiresorptive agents may generate concerns, because of the risk of inducing oversuppression of bone turnover. However, if low doses of estrogen, used for the management of climacteric symptoms, are insufficient to normalize bone turnover, the addition of a bisphosphonate to hormone therapy may prove to be useful to achieve this objective. Patients pretreated with inhibitors of resorption, who have not achieved a full therapeutic response, are good candidates for treatment with anabolic agents. The increase in bone turnover that comes after the introduction of parathyroid hormone (PTH) in patients treated with an antiresorptive agent is similar to that observed in treatment-naive patients and the pattern of bone mineral density (BMD) increase is also identical, with the exception of a 6 month delay in the spine and hip BMD changes observed in prior alendronate-treated subjects. Current data discourage the concomitant use of alendronate and PTH since the bisphosphonate appears to blunt (in men and women) the anabolic action of PTH. Whether this applies to other bisphosphonates or inhibitors of resorption, remains unknown. The use of an inhibitor of bone resorption after completion of PTH treatment seems an appropriate way to maintain the skeletal benefits gained during therapy. Long-term clinical studies, using fractures as an endpoint should be initiated to better understand the clinical and pharmaco-economic interest of combination therapies in the management of osteoporosis. [less ▲]

Detailed reference viewed: 17 (2 ULg)
Full Text
Peer Reviewed
See detailA combinatorial branch-and-bound algorithm for box search
Mathieu, Sébastien ULg; Louveaux, Quentin ULg

in Discrete Optimization (2014), 13

Considering a set of points in a multi-dimensional space with an associated real value for each point, we want to find the box with the maximum sum of the values of the included points. This problem has ... [more ▼]

Considering a set of points in a multi-dimensional space with an associated real value for each point, we want to find the box with the maximum sum of the values of the included points. This problem has applications in data mining and can be formulated as a mixed-integer linear program. We propose a branch-and-bound algorithm where the bounding is obtained by combinatorial arguments instead of the traditional linear relaxation. Computational experiments show that this approach competes with current state of the art mixed-integer solvers. The algorithm proposed in this paper may be seen as a simple and dependence-free method to solve the box search problem. [less ▲]

Detailed reference viewed: 60 (22 ULg)
Full Text
Peer Reviewed
See detailCombinatorial optimization approaches to the design of load shedding schemes against voltage instability
Moors, Cédric; Lefebvre, Daniel; Van Cutsem, Thierry ULg

(2000, October)

This paper proposes a methodology for the design of automatic load shedding against long-term voltage instability. In a first step, a set of training scenarios is set up, corresponding to various ... [more ▼]

This paper proposes a methodology for the design of automatic load shedding against long-term voltage instability. In a first step, a set of training scenarios is set up, corresponding to various operating conditions and disturbances. Each scenario is analyzed to determine the minimal load shedding which stabilizes the system, with due consideration for the shedding location and delay. In a second step, the parameters of a closed-loop undervoltage load shedding scheme are determined so as to: (i) approach as closely as possible the optimal sheddings computed in the first step, over the whole set of scenarios; (ii) stabilize the system in all the unstable scenarios and (iii) shed no load in the stable ones. The corresponding optimization problem is solved using three methods : genetic algorithms, branch and bound approach and the so-called “sequential design”. A detailed example is given on the Hydro-Qu´ebec system in which load shedding is presently planned. [less ▲]

Detailed reference viewed: 49 (5 ULg)
Full Text
See detailCombinatorial Optimization Models in Automated Manufacturing
Crama, Yves ULg

Conference (2010, April 01)

Detailed reference viewed: 11 (3 ULg)
Full Text
Peer Reviewed
See detailA combinatorial proof of $S$-adicity for sequences with linear complexity
Leroy, Julien ULg; Richomme, Gwenaël

in Integers: Electronic Journal of Combinatorial Number Theory (2013), 13

Detailed reference viewed: 14 (0 ULg)
Full Text
Peer Reviewed
See detailCombinatorics, Automata and Number Theory 2006
Berthé, Valérie; Lecomte, Pierre ULg; Rigo, Michel ULg

in Theoretical Computer Science (2008), 391

Detailed reference viewed: 18 (5 ULg)
See detailCombine pedigree and marker information into a single estimator for the calculation of relationships
Bömcke, Elisabeth ULg; Gengler, Nicolas ULg

Poster (2009, May)

Relationship coefficients are particularly useful to improve genetic management of endangered populations. Estimation of relationships was traditionally based on pedigree data but, today, numerous methods ... [more ▼]

Relationship coefficients are particularly useful to improve genetic management of endangered populations. Estimation of relationships was traditionally based on pedigree data but, today, numerous methods already exist to replace pedigrees by molecular data. However, genotyping a complete population for a sufficient number of markers can be impossible, e.g., in case of local and/or rare breeds. The idea was therefore to develop a new method to estimate relationship by combining molecular with pedigree data into a single estimator. Originally developed for the management of an endangered horse population, it will be useful for specific situations, where neither pedigree nor molecular data are complete. Two questions appeared: What and how to combine? Following the principle that things have to be similar to be combined, we compared two coefficients that have the advantage to be similarly defined: the additive relationship coefficient (axy) calculated from pedigrees and the total allelic relationship (taxy) obtained from markers. Wright relationship coefficient (rped,xy) were also compared to taxy, transformed into rmol,xy, to highlight the influence of inbreeding. The results showed the influence of inbreeding, of marker quality and the tendency of molecular coefficients to overestimate the relationship among individuals. The method to combine the selected coefficients was also determined. Various parameters were taken into account in the model: number of markers and quality (e.g. marker informativeness), mutation rate, pedigree quality (e.g. generation-equivalents), … The combined estimator has several advantages. Especially, negative relationship values obtained in literature with molecular-based estimators in case of small inbred populations can be avoided. [less ▲]

Detailed reference viewed: 34 (5 ULg)