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See detailNew Methode for a Two-Step Hydrolysis and Chromatographic Analysis of Pectin Neutral Sugar Chains
Haikel, Garna; Mabon, Nicolas ULg; Wathelet, Bernard ULg et al

in Journal of Agricultural and Food Chemistry (2004), 52

Detailed reference viewed: 14 (2 ULg)
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See detailA new methodological approach for error distributions selection in Finance
Hambuckers, julien ULg; Heuchenne, Cédric ULg

Conference (2014, April)

In this article, we propose a robust methodology to select the most appropriate error distribution candidate, in a classical multiplicative heteroscedastic model. In a first step, unlike to the ... [more ▼]

In this article, we propose a robust methodology to select the most appropriate error distribution candidate, in a classical multiplicative heteroscedastic model. In a first step, unlike to the traditional approach, we don't use any GARCH-type estimation of the conditional variance. Instead, we propose to use a recently developed nonparametric procedure (Mercurio and Spokoiny, 2004): the Local Adaptive Volatility Estimation (LAVE). The motivation for using this method is to avoid a possible model misspecification for the conditional variance. In a second step, we suggest a set of estimation and model selection procedures (Berk-Jones tests, kernel density-based selection, censored likelihood score, coverage probability) based on the so-obtained residuals. These methods enable to assess the global fit of a given distribution as well as to focus on its behavior in the tails. Finally, we illustrate our methodology on three time series (UBS stock returns, BOVESPA returns and EUR/USD exchange rates). [less ▲]

Detailed reference viewed: 46 (19 ULg)
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See detailA new methodological approach for error distributions selection in Finance
Hambuckers, julien ULg; Heuchenne, Cédric ULg

E-print/Working paper (2014)

In this article, we propose a robust methodology to select the most appropriate error distribution candidate, in a classical multiplicative heteroscedastic model. In a first step, unlike to the ... [more ▼]

In this article, we propose a robust methodology to select the most appropriate error distribution candidate, in a classical multiplicative heteroscedastic model. In a first step, unlike to the traditional approach, we don't use any GARCH-type estimation of the conditional variance. Instead, we propose to use a recently developed nonparametric procedure (Mercurio and Spokoiny, 2004): the Local Adaptive Volatility Estimation (LAVE). The motivation for using this method is to avoid a possible model misspecification for the conditional variance. In a second step, we suggest a set of estimation and model selection procedures (Berk-Jones tests, kernel density-based selection, censored likelihood score, coverage probability) based on the so-obtained residuals. These methods enable to assess the global fit of a given distribution as well as to focus on its behavior in the tails. Finally, we illustrate our methodology on three time series (UBS stock returns, BOVESPA returns and EUR/USD exchange rates). [less ▲]

Detailed reference viewed: 27 (14 ULg)
See detailA new methodological approach for error distributions selection
Hambuckers, julien ULg; Heuchenne, Cédric ULg

Scientific conference (2013, November)

Since 2008 and its financial crisis, an increasing attention has been devoted to the selection of an adequate error distribution in risk models, in particular for Value-at-Risk (VaR) predictions. We ... [more ▼]

Since 2008 and its financial crisis, an increasing attention has been devoted to the selection of an adequate error distribution in risk models, in particular for Value-at-Risk (VaR) predictions. We propose a robust methodology to select the most appropriate error distribution candidate, in a classical multiplicative heteroscedastic model. In a first step, unlike to the traditional approach, we do not use any GARCH-type estimation of the conditional variance. Instead, we propose to use a recently developed nonparametric procedure: the Local Adaptive Volatility Estimation (LAVE). The motivation for using this method is to avoid a possible model misspecification for the conditional variance. In a second step, we suggest a set of estimation and model selection procedures tests based on the so-obtained residuals. These methods enable to assess the global fit of a given distribution as well as to focus on its behaviour in the tails. Finally, we illustrate our methodology on three time series (UBS stock returns, BOVESPA returns and EUR/USD exchange rates). [less ▲]

Detailed reference viewed: 19 (4 ULg)
Peer Reviewed
See detailA new methodological approach for error distributions selection
Hambuckers, julien ULg; Heuchenne, Cédric ULg

Conference (2013, December 15)

Since 2008 and its financial crisis, an increasing attention has been devoted to the selection of an adequate error distribution in risk models, in particular for Value-at-Risk (VaR) predictions. We ... [more ▼]

Since 2008 and its financial crisis, an increasing attention has been devoted to the selection of an adequate error distribution in risk models, in particular for Value-at-Risk (VaR) predictions. We propose a robust methodology to select the most appropriate error distribution candidate, in a classical multiplicative heteroscedastic model. In a first step, unlike to the traditional approach, we do not use any GARCH-type estimation of the conditional variance. Instead, we propose to use a recently developed nonparametric procedure: the Local Adaptive Volatility Estimation (LAVE). The motivation for using this method is to avoid a possible model misspecification for the conditional variance. In a second step, we suggest a set of estimation and model selection procedures tests based on the so-obtained residuals. These methods enable to assess the global fit of a given distribution as well as to focus on its behaviour in the tails. Finally, we illustrate our methodology on three time series (UBS stock returns, BOVESPA returns and EUR/USD exchange rates). [less ▲]

Detailed reference viewed: 16 (7 ULg)
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See detailA new methodological approach to try to link past disturbances and modern landscapes
Bourland, Nils ULg; Livingstone Smith, Alexandre; Doucet, Jean-Louis ULg

in Primate Tidings (2011, July), 24

Detailed reference viewed: 25 (10 ULg)
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See detailNew methodology for generating realistic data for evaluation of performance of radar STAP algorithms
Ries, Philippe; Tey, Shuwen; Verly, Jacques ULg et al

Conference (2007)

Detailed reference viewed: 5 (0 ULg)
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See detailNew Methodology for the Development of Chromatographic Methods
Rozet, Eric ULg; Debrus, Benjamin ULg; Lebrun, Pierre ULg et al

Conference (2011, September 08)

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. Acknowledgements A research grant from the Belgium National Fund for Scientific Research (F.R.S-FNRS) to E. Rozet is gratefully acknowledged. [less ▲]

Detailed reference viewed: 47 (7 ULg)
Peer Reviewed
See detailA new methodology to analyse monthly somatic cell counts
Detilleux, Johann ULg; Volckaert, D.; Leroy, Pascal ULg

(1998)

Detailed reference viewed: 7 (1 ULg)
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See detailNew Methodology to detect toxin-GPCR binding by MALDI-TOF Mass Spectrometry
Echterbille, Julien ULg; De Pauw, Edwin ULg; Gilles, Nicolas et al

Poster (2011)

Introduction More than 50 thousands of venomous species are currently indexed in the world. Each of their venoms is composed of 200 to 1000 different toxins which potentially exhibit a high selectivity ... [more ▼]

Introduction More than 50 thousands of venomous species are currently indexed in the world. Each of their venoms is composed of 200 to 1000 different toxins which potentially exhibit a high selectivity for membrane receptors such as ionic channels or G-protein coupled receptors (GPCRs). GPCRs constitute the larger family of receptors since around 800 different kinds of them are knows. GPCRs are the target of around 30% of the current pharmacopeia drugs. Notable examples include Novartis’s Zelnorm, Eli Lilly’s Zyprexa and Schering-Plough’s Clarinex used to treat constipation, schizophrenia and allergies, respectively. Finding new GPCRs ligands appears of prime interest to design new pharmacological tools and potentially discover the drugs of our future. Interestingly, several toxins from venoms have already been described to bind to this particular family of receptor, opening the way to the discovery of new peptide drugs from animal venoms1-2. This work presents a pioneering MALDI-TOF/TOF based strategy to fish new GPCRs ligands from complex mixtures such as venom fractions. Methods The proof of concept of this methodology was built by studying the binding of [Arg8]-vasopressin (AVP) on type 2-vasopressin receptor (V2). Experimentally, fragments of cellular membranes over-expressing V2 receptors were incubated with cone snail’s venom fraction (~30 peptide toxins) doped by a small amount of AVP. After 2 hours incubation, free and bound fractions were carefully purified with a combination of centrifugation and micro column purifications. Samples were finally analyzed with a Bruker Ultraflex II MALDI-TOF/TOF mass spectrometer and the resulting spectra were interpreted with FlexAnalysis (v3.0), BioTools (v3.2) and SequenceEditor (v3.2) bioinformatics’ softwares from Bruker Daltonics. Preliminary data After the incubation of cellular membranes overexpressing V2 GPCR with a complex mixture of peptides doped by AVP, we clearly detect that the only V2 ligand present in the fraction was the AVP. Our result demonstrates the possibility to identify a ligand of GPCRs from a complex peptide mixture, such as venom fractions. Contrary to radiobinding, this approach allows detecting the direct binding of the toxin and does not imply to know a ligand of the studied GPCR before starting the experiments. This opens the way to the deorphanization of receptors (180 orphans GPCRs over 800). Moreover, since the new ligand is detected by mass spectrometry, it is directly identified from the mixture, without additional purification. Its structural characterization can be directly performed by de novo sequencing experiments. The drawback of our approach is the very long (but crucial!) sample preparation as each sample requires 2 purification steps (for both free and bound fraction). The next step of our work will be the automation of the procedure to allow a high-throughput screening of venom fractions on different GPCRs and the discovery of new ligands. Novel aspect GPCR’s ligands discovery by MALDI-TOF/TOF based techniques: a new pharmacological tool. 1 Quinton, L. et al. Isolation and pharmacological characterization of AdTx1, a natural peptide displaying specific insurmountable antagonism of the a1A-adrenoceptor. British Journal of Pharmacology 159, 316-325 (2010). 2 Rouget, C. et al. Identification of a novel snake peptide toxin displaying high affinity and antagonist behaviour for the α2-adrenoceptors. British Journal of Pharmacology 161, 1361-1374, doi:10.1111/j.1476-5381.2010.00966.x (2010). [less ▲]

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See detailNew Methods For Halogenation of [18F]Fluorinated Benzyl Derivatives.
Kech, C.; Lemaire, Christian ULg; Brichard, L. et al

in Journal of Labelled Compounds & Radiopharmaceuticals (2005), 48

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See detailNew methods for handling the range dependence of the clutter spectrum in non-sidelooking monostatic STAP radars
Lapierre, Fabian; Van Droogenbroeck, Marc ULg; Verly, Jacques ULg

in International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2003), Proceedings, Volume 5 (2003, April)

We address the problem of detecting slow-moving targets using a non-sideloking monostatic space-time adaptive processing (STAP) radar. The construction of optimum weights at each range implies the ... [more ▼]

We address the problem of detecting slow-moving targets using a non-sideloking monostatic space-time adaptive processing (STAP) radar. The construction of optimum weights at each range implies the estimation of the clutter covariance matrix. This is typically done by straight averaging of neighboring data snapshots. The range-dependence of these snapshots generally results in poor performance. We present two new methods that handle the rangedependence by exploiting the geometry of the direction-Doppler curves. [less ▲]

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See detailNew methods of prenatal screening for trisomy 21
Capelle, Xavier ULg; Schaaps, Jean-Pierre ULg; Foidart, Jean-Michel ULg

in Revue Médicale de Liège (2008), 63(2), 82-6

Down syndrome is the most commonly recognized genetic cause of mental retardation. The risk of trisomy 21 is directly related to maternal age which can be viewed as the first screening test in the 1970's ... [more ▼]

Down syndrome is the most commonly recognized genetic cause of mental retardation. The risk of trisomy 21 is directly related to maternal age which can be viewed as the first screening test in the 1970's. New strategies for Down syndrom, have emerged with higher sensitivity and lower false-positive rate. These strategies are based on sonographic and maternal serum markers. The most specific but complex strategy is based on the integrated test, i.e., the integration of the quadruple test performed in the second trimester to the first trimester combined screening: for a 85% detection rate, the false positive rate is estimated to 0.9%. This strategy deprives the patient of an early diagnosis. Alternatives strategies do exist which can perform similar detection rate but with increasing false positive rate. To date Down syndrom, screening has not been coordinated by a national body; it would be usefull to ensure the sonographist formation, perform quality audit and decrease variations in practice. [less ▲]

Detailed reference viewed: 103 (5 ULg)
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See detaila new methylxanthine lisofylline increases radiosensitivity in air and hypoxia
Coucke, Philippe ULg; Crompton; Greiner et al

Scientific conference (1998, March 04)

Detailed reference viewed: 6 (0 ULg)
See detailNew Migration and Intergation in Europe
Martiniello, Marco ULg

Scientific conference (2011, September 29)

Detailed reference viewed: 22 (2 ULg)
See detailNew Migration and new Migrants in Belgium
Martiniello, Marco ULg

Scientific conference (2009, June 11)

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See detail“New Migrations and New Migrants in Belgium”
Martiniello, Marco ULg

Scientific conference (2008, February 01)

Detailed reference viewed: 4 (0 ULg)
See detailThe new migratory Europe: towards a proactive immigration policy?
Martiniello, Marco ULg

in Parsons, Craig; Smeeding, Timothy (Eds.) Immigration and the Transformation of Europe (2006)

Detailed reference viewed: 60 (4 ULg)